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Title: 3-phase power demonstration
Post by: Mike Sokol on December 06, 2018, 07:32:33 pm
I was just contacted by a company that wants me to train their crew and make a video for them on the differences between the main 3-phase transformer connections, and how to recognize them in the field. Yup, I need to get them up to speed on how to recognize and measure Delta, Wye and Wild-Leg Delta services, as well as 2-pole 120/240-volt service.

Of course it's easy enough for me to create a nice Powerpoint presentation, but I always say that nothing beats a real example. So I'm envisioning how to build a tiny 3-phase signal generator that will make 120/208 volts in WYE, Delta or High-Leg, in a place that doesn't have 3-phase power.

So the thought occurred to me that all I have to do is take any multi-track mixing program, generate a 10 minute track of a 60 Hz sine wave, duplicate it on tracks 2 and 3, then slip those tracks back 120 and 240 degrees out of phase. Then I just output the 3 audio tracks on 3 outputs of an I/O interface like my MOTU Audio Express. Next, I hook up three 120/240-volt primary filament transformers with the 6.3-volt side being driven by the TRS outputs on the MOTU. Finally, I can wire the 120/240-volt sides of the transformers into Delta, Wye or High-Leg Delta configurations with a few banana plugs. Of course, the MOTU can't drive any real amperage through the transformers. But I just need it to make 3-phase voltage in the 120 volt range that can be measured with a DMM.

I don't see why it won't work. Has anyone here tried something like this?     
Title: Re: 3-phase power demonstration
Post by: Tim McCulloch on December 06, 2018, 08:25:09 pm
Ask yourself "WWNTD"  What Would Nicola Tesla Do?
 
Title: Re: 3-phase power demonstration
Post by: Riley Casey on December 06, 2018, 09:14:58 pm
Nicola would claim wireless was better

Ask yourself "WWNTD"  What Would Nicola Tesla Do?
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on December 06, 2018, 09:22:14 pm
Ask yourself "WWNTD"  What Would Nicola Tesla Do?
Well, Tesla always said he knew his inventions would work just envisioning them in his mind. He only had to do demonstrations to prove it to other people.

Title: Re: 3-phase power demonstration
Post by: Frank Koenig on December 07, 2018, 01:09:43 am
Another approach would be to get your hands on a small, fractional-horsepower three-phase motor. These will work as a (not very good) single-phase motor with power applied to one of the three windings if you give them a spin to get started, which you could do with a starter cord and pully, a la lawnmower (good for dramatic effect). The other two windings will produce power suitably shifted in phase. You would still need a center-tapped transformer to simulate high-leg delta.

--Frank
Title: Re: 3-phase power demonstration
Post by: Marc Sibilia on December 07, 2018, 06:35:51 am
Next, I hook up three 120/240-volt primary filament transformers with the 6.3-volt side being driven by the TRS outputs on the MOTU.
...
Of course, the MOTU can't drive any real amperage through the transformers.

I don't see why it won't work. Has anyone here tried something like this?     

I don't think you will get your 120/240V output without some amplification.  The outputs of the MOTU probably have some current limiting resistors for short circuit protection and they will drop most of the voltage with a low impedance load.  You could use a couple of cheap (under $25) Lepai 2020 amplifiers ( ~ 15 watts into 4 ohms) as buffers, as well as a form of protection for your nice interface.  They should work well for driving some 1A 6.3V transformers.

P.S. It will work. I just tried it with a 6.3 V 3A transformer and a Lepai, and it was pulling 0.35A on the 6.3V "primary" with no load on the 120V secondary.  It takes slightly more than 6.3V on the primary to get 120V on the secondary.  That's easy to adjust with the volume control.  The good thing about the Lepai is it will only do about 8 Vrms output, so the insulation on the transformer is relatively safe from stupid mistakes on input level.

Be careful and methodical (I don't think I need to tell you this, but it is for people following along).  With 240 V secondaries, you could see voltages of almost 1 kVrms with the worst case output wiring and input signal phasing.  This would likely comprimise one or more of the transformers' insulation, and may be more than the voltmeter's rated voltage.
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on December 07, 2018, 08:12:59 am
Another approach would be to get your hands on a small, fractional-horsepower three-phase motor. These will work as a (not very good) single-phase motor with power applied to one of the three windings if you give them a spin to get started, which you could do with a starter cord and pully, a la lawnmower (good for dramatic effect). The other two windings will produce power suitably shifted in phase. You would still need a center-tapped transformer to simulate high-leg delta.

--Frank

I'm pretty sure that all car alternators are 3-phase generators with a WYE winding configuration and a bunch of diodes to make DC. So all I would have to do is pull out the diodes and add a DC control voltage to the alternator rotor winding to adjust the output voltage on the stator windings. I could spin this with any kind of 120-volt motor, and add 12 volt to 120-volt filament transformers to create floating transformer secondaries just like POCO transformers in reverse. I can get a really small car alternator for $50 or so, an AC motor for another $20 and three filament transformers with 120/120 volt primary windings for maybe $20 each. I've got to take this as checked luggage on a plane so it could be mounted on a plate that would fit in a pelican case. The advantage of this type of rig is that it's more obvious to electrical power students than running Reaper on a Mac through an I/O interface. Plus it would be a good chance to demonstrate how 3-phase generators work. In addition, if the filament transformers were hefty enough it could easily generate a few amps of current per output for more interesting experiments such as what happens when the neutral opens up, etc...

The Mechanical Engineer inside of me wants to build this. 
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on December 07, 2018, 08:20:34 am
I don't think you will get your 120/240V output without some amplification.  The outputs of the MOTU probably have some current limiting resistors for short circuit protection and they will drop most of the voltage with a low impedance load.  You could use a couple of cheap (under $25) Lepai 2020 amplifiers ( ~ 15 watts into 4 ohms) as buffers, as well as a form of protection for your nice interface.  They should work well for driving some 1A 6.3V transformers.

P.S. It will work. I just tried it with a 6.3 V 3A transformer and a Lepai, and it was pulling 0.35A on the 6.3V "primary" with no load on the 120V secondary.  It takes slightly more than 6.3V on the primary to get 120V on the secondary.  That's easy to adjust with the volume control.  The good thing about the Lepai is it will only do about 8 Vrms output, so the insulation on the transformer is relatively safe from stupid mistakes on input level.

Be careful and methodical (I don't think I need to tell you this, but it is for people following along).  With 240 V secondaries, you could see voltages of almost 1 kVrms with the worst case output wiring and input signal phasing.  This would likely compromise one or more of the transformers' insulation, and may be more than the voltmeter's rated voltage.

The Lepai amps are a good tip. I was wondering about the actual impedance of the 6.3 volt transformers being so low that it would excessively load the output stage of the I/O interface. I'm sure there's current-limiting build-out resistors on the MOTU box which would probably drop the voltage swing too much since it's expecting a 600-ohm load at minimum. Looks like the amps are $22 each, so that's a cheap fix: https://www.amazon.com/Lepy-Amplifiers-Component-LP-2020A-Class-D/dp/B01FZKA28Y/ref=sr_1_fkmr0_1?ie=UTF8&qid=1544188691&sr=8-1-fkmr0&keywords=lepai+amplifier+quad

The Lepai amplifiers actually sound pretty decent. I bought one last Christmas for my son's television set to drive a pair of passive speakers, and it worked very well. Working backwards and considering basic efficiency losses, this should easily produce maybe 5 watts (500 mA) per leg on the 120/208 side of the filament transformers. 

And yes, I would fuse everything properly and consider insulation breakdown voltages. And even something as innocent looking as this can produce lethal voltages and currents. I know that you know that I know this, but you are correct that we need to remind all the possible readers about the hazards of playing with live electrical circuits. As I like to say, "Kids don't try this at home". 

The Electrical/Audio Engineer inside of me really wants to build this. 
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on December 07, 2018, 09:42:31 am
I think these transformers would work nicely. If I'm thinking about this correctly, I need the transformer "outputs" to be 120-volts for the 120/208 WYE configuration, and 240-volts with one of them center-tapped for the 120/240 Delta High-Leg configuration. The beauty of doing this with something like Reaper as a multi-track player is that I could let the class see the three sine waves on the computer screen and actually measure the voltage across the various transformer legs as I slip the track phases. That could be really educational, I think.

Title: Re: 3-phase power demonstration
Post by: Ron Hebbard on December 07, 2018, 09:43:02 am
The Lepai amps are a good tip. I was wondering about the actual impedance of the 6.3 volt transformers being so low that it would excessively load the output stage of the I/O interface. I'm sure there's current-limiting build-out resistors on the MOTU box which would probably drop the voltage swing too much since it's expecting a 600-ohm load at minimum. Looks like the amps are $22 each, so that's a cheap fix: https://www.amazon.com/Lepy-Amplifiers-Component-LP-2020A-Class-D/dp/B01FZKA28Y/ref=sr_1_fkmr0_1?ie=UTF8&qid=1544188691&sr=8-1-fkmr0&keywords=lepai+amplifier+quad

The Lepai amplifiers actually sound pretty decent. I bought one last Christmas for my son's television set to drive a pair of passive speakers, and it worked very well. Working backwards and considering basic efficiency losses, this should easily produce maybe 5 watts (500 mA) per leg on the 120/208 side of the filament transformers. 

And yes, I would fuse everything properly and consider insulation breakdown voltages. And even something as innocent looking as this can produce lethal voltages and currents. I know that you know that I know this, but you are correct that we need to remind all the possible readers about the hazards of playing with live electrical circuits. As I like to say, "Kids don't try this at home". 

The Electrical/Audio Engineer inside of me really wants to build this.
Will you demonstrate "Scott T" interconnections as well? 
Toodleoo! 
Ron Hebbard
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on December 07, 2018, 10:08:00 am
Will you demonstrate "Scott T" interconnections as well? 
Toodleoo! 
Ron Hebbard

Wow, I remember reading about this really ingenious phase conversion circuit many years ago, but I've never encountered one in the wild since its only needed for 2-phase/90-degree power. Basically it's a really cool offset-tapped transformer setup that converts 2-phase (90 degree) power to 3-phase (120-degree power). This was invented in the 1890's to get around one of Edison's patents on rotary-phase converters.

However, I don't think it's relevant for a classroom of A-V technicians who need to measure 3-phase power for sound and lighting since 2-phase power in the US is extremely rare. However, this would make a really cool video demonstration showing the historic differences between single-phase, 2-phase and 3-phase power transmission and usage.

See more at https://en.wikipedia.org/wiki/Scott-T_transformer
Title: Re: 3-phase power demonstration
Post by: Frank Koenig on December 07, 2018, 10:11:53 am
I'm pretty sure that all car alternators are 3-phase generators with a WYE winding configuration and a bunch of diodes to make DC.

That's a great idea. It will take some surgery to get ahead of the rectifier diodes that are pressed into the alternator housing for heatsinking. The low voltage makes it (relatively) safe for banana plug patching. -F

You'll also need a source of excitation for the field unless you can find a permanent magnet alternator.
Title: Re: 3-phase power demonstration
Post by: Nathan Riddle on December 07, 2018, 10:23:31 am
Hobbyking.com has 3p motors for their RC stuff.

https://hobbyking.com/en_us/turnigy-2211-brushless-indoor-motor-2300kv.html

https://www.rcgroups.com/forums/showthread.php?666877-Rewinding-brushless-motors-WYE-or-Delta

But I think the transformer method will be safest/easiest to demonstrate (no moving parts) [atleast there shouldn't be any :P]
Title: Re: 3-phase power demonstration
Post by: Jay Barracato on December 07, 2018, 10:27:25 am
If you are doing this with students, hook the alternator up to a bicycle and make them pedal a la Gilligan's island.

They will remember...

Sent from my Moto Z (2) using Tapatalk

Title: Re: 3-phase power demonstration
Post by: Mike Sokol on December 07, 2018, 10:36:17 am
If you are doing this with students, hook the alternator up to a bicycle and make them pedal a la Gilligan's island.

They will remember...

Sent from my Moto Z (2) using Tapatalk

So these students will be working A-V technicians like you guys and gals are. I think I should send to power to a 3-phase load center like this one, so I can show various 1-p, 2-p and 3-p circuit breakers. Of course the MOTU I/O method would only make perhaps 50mA per leg at 120 volts, but a car alternator could possibly make at least a few amperes per leg. More to think about.

Title: Re: 3-phase power demonstration
Post by: Tim McCulloch on December 07, 2018, 12:02:42 pm
If you are doing this with students, hook the alternator up to a bicycle and make them pedal a la Gilligan's island.

They will remember...

Sent from my Moto Z (2) using Tapatalk

That's where I was heading... damn mind reader! 
Title: Re: 3-phase power demonstration
Post by: Tim McCulloch on December 07, 2018, 12:23:12 pm
So these students will be working A-V technicians like you guys and gals are. I think I should send to power to a 3-phase load center like this one, so I can show various 1-p, 2-p and 3-p circuit breakers. Of course the MOTU I/O method would only make perhaps 50mA per leg at 120 volts, but a car alternator could possibly make at least a few amperes per leg. More to think about.

I have a buddy who rented space in a retail strip center and opened a little bar & grill.  The dividing walls had been moved a couple of times and some of his dining room outlets were powered by the business next door, but when he needed a few more circuits behind the bar he noticed that every 3rd breaker space in his panel was unused so he used those blank spaces for new circuits.  He did the work, didn't call an electrician or pull a permit.

After a few "magic smoke" episodes he called me to take a look.  Phase line conductors were marked Black, Red, Orange.  A quick demonstration with a volt meter confirmed high-leg Delta service to his panel.  The Emperor's New Circuits were 208v.
Title: Re: 3-phase power demonstration
Post by: Chris Hindle on December 07, 2018, 12:38:17 pm

You'll also need a source of excitation for the field unless you can find a permanent magnet alternator.
That would be a generator, not an alternator.
I think it was early 60's that Alternators came into use.
Before that, it was DC Generators.
Chris.
Title: Re: 3-phase power demonstration
Post by: Stephen Swaffer on December 07, 2018, 12:57:22 pm
So these students will be working A-V technicians like you guys and gals are. I think I should send to power to a 3-phase load center like this one, so I can show various 1-p, 2-p and 3-p circuit breakers. Of course the MOTU I/O method would only make perhaps 50mA per leg at 120 volts, but a car alternator could possibly make at least a few amperes per leg. More to think about.

You need to add an islated neutral bus to do this right.-as it is pictued that panel is only acceptable for delta connected loads.
Title: Re: 3-phase power demonstration
Post by: Frank Koenig on December 07, 2018, 02:29:10 pm
That would be a generator, not an alternator.

I disagree. Automotive ALTERNATORS, in my experience, use a field winding on the rotor powered through slip rings. The output voltage, derived from the 3-phase stator and a 3-phase rectifier, is controlled by varying the field current.  They could use a permanent magnet field but would need to apply voltage regulation downstream, as by PWM.

The GENERATORS of yesteryear had a field winding in the stator, and took the output from multiple windings on the rotor through a commutator.

The whole nomenclature of what constitutes an AC or DC machine has become blurry in recent years with the widespread use of electronic motor/generator drives.  -F
Title: Re: 3-phase power demonstration
Post by: Chris Hindle on December 07, 2018, 02:51:56 pm
I disagree. Automotive ALTERNATORS, in my experience, use a field winding on the rotor powered through slip rings. The output voltage, derived from the 3-phase stator and a 3-phase rectifier, is controlled by varying the field current.  They could use a permanent magnet field but would need to apply voltage regulation downstream, as by PWM.

The GENERATORS of yesteryear had a field winding in the stator, and took the output from multiple windings on the rotor through a commutator.

The whole nomenclature of what constitutes an AC or DC machine has become blurry in recent years with the widespread use of electronic motor/generator drives.  -F
Agreed to your points Frank.
As I retired mechanic, Generators were 50's, and Alternators 60's and newer.
Never had to rebuild a Genny, but have done a shit load of Delco's over the years. Mostly brushes and/or Modules. Those diodes were indestructible.

That they COULD have used PM instead of windings would have just made them heavier, and didn't PWM controls start in the 80's ?
Chris.
Title: Re: 3-phase power demonstration
Post by: Frank Koenig on December 07, 2018, 03:21:48 pm
That they COULD have used PM instead of windings would have just made them heavier, and didn't PWM controls start in the 80's ?

Yes. Heavier, probably more expensive, maybe thermal issues, and auto manufacturers hate to change anything that's still getting product out the door unless they find a far cheaper way to make it. (Why are there still drum brakes in 2018?)

As an aside, last winter I visited both hydroelectric plants at Bonneville on the Columbia River. In the older plant they had replaced the exciter generators with semiconductor rectifiers. The exciter rectifiers for an alternator the size of a small house are air cooled and fit in an ~15 ft wide standing height cabinet.

-Frank
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on December 07, 2018, 04:06:30 pm
Just talked to their training manager and they’re excited about the possibility of having real 3-phase power in all the flavors to measure. And I get to do a full 8-hour training day. This could be a lot of fun.
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on December 07, 2018, 04:10:10 pm
You need to add an islated neutral bus to do this right.-as it is pictued that panel is only acceptable for delta connected loads.
Yeah, that wouldn’t be too difficult considering there will only be a few hundred mA of current. Or I could bring a rack of MacroTech amplifiers and make some real juice.
Title: Re: 3-phase power demonstration
Post by: Chris Hindle on December 07, 2018, 05:44:20 pm
Yeah, that wouldn’t be too difficult considering there will only be a few hundred mA of current. Or I could bring a rack of MacroTech amplifiers and make some real juice.
And here I was thinking 3 sine wave oscillators and 3 DC-300's  ::)
Chris.
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on December 09, 2018, 07:41:19 am
And here I was thinking 3 sine wave oscillators and 3 DC-300's  ::)
Chris.

IIRC decades ago one of the companies I worked with used a Crown DC300 to drive big servo motors on a vibration platform. Don’t they go down to actual DC output because their’s no HPF in their signal path? Bad for speakers, good for servo motors...
Title: Re: 3-phase power demonstration
Post by: Chris Hindle on December 10, 2018, 08:39:42 am
IIRC decades ago one of the companies I worked with used a Crown DC300 to drive big servo motors on a vibration platform. Don’t they go down to actual DC output because their’s no HPF in their signal path? Bad for speakers, good for servo motors...
I believe that was the DC in the product name. They WOULD go to DC.
That was the default failure mode, and would wipe out a batch of drivers in a real hurry. Not as spectacular as a Flame Linear, but just as damaging....
On 1 rig, we lost 3 of 12 2441's when a DC300 took a dump.
Ahhh, the good old dayze....
Chris.
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on December 11, 2018, 08:33:20 am
I believe that was the DC in the product name. They WOULD go to DC.
That was the default failure mode, and would wipe out a batch of drivers in a real hurry. Not as spectacular as a Flame Linear, but just as damaging....
On 1 rig, we lost 3 of 12 2441's when a DC300 took a dump.
Ahhh, the good old dayze....
Chris.

I'm going to talk to my contact at Crown and see if they'll loan me a CT475 amp for the class: https://www.crownaudio.com/en/products/ct-475

This is a quad 1RU amp that outputs 75 watts per channel into 8 ohms, so it would match up nicely with air conditioner transformers that are 120/240-volts to 24-volts. And these transformers come in 40 or 50VA size which would match up nicely with the amplifier outputs. The only advantage of using a bigger amplifier would be that I could do a few current experiments that would be iffy on a little 10-watt amplifier. In any event, I'm going to draw up a schematic and block diagram in a few days to make sure I'm not missing anything. It's all in my head right now, so it's time to put this down on paper.
Title: Re: 3-phase power demonstration
Post by: Chris Hindle on December 11, 2018, 08:54:20 am
I'm going to talk to my contact at Crown and see if they'll loan me a CT475 amp for the class: https://www.crownaudio.com/en/products/ct-475

This is a quad 1RU amp that outputs 75 watts per channel into 8 ohms, so it would match up nicely with air conditioner transformers that are 120/240-volts to 24-volts. And these transformers come in 40 or 50VA size which would match up nicely with the amplifier outputs. The only advantage of using a bigger amplifier would be that I could do a few current experiments that would be iffy on a little 10-watt amplifier. In any event, I'm going to draw up a schematic and block diagram in a few days to make sure I'm not missing anything. It's all in my head right now, so it's time to put this down on paper.
Gotta say Mike, you sure get to theorize and build some pretty cool "stuff".
Good on ya, and the education you spread to others. (me included).
I got to blow up a lot of shit learning what I know...
Long before this interwebby thing came along....
Chris.
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on December 11, 2018, 09:37:19 am
Gotta say Mike, you sure get to theorize and build some pretty cool "stuff".
Good on ya, and the education you spread to others. (me included).
I got to blow up a lot of shit learning what I know...
Long before this interwebby thing came along....
Chris.

This really is too much fun!

Now what I need to consider is how to take the three transformer secondaries and rewire them as WYE, Delta or High-Leg Delta services at the flip of a switch. I'm not sure I trust myself to use banana plugs to rewire the various configurations while simultaneously teaching a seminar. Of course I could do the Rick Wakeman brute force method and have 9 transformers feeding 3 different service panels with everything wired at once, but that seems like cheating and too heavy to take on a plane. Looks like I need to remember Boolean Algebra and Karnaugh maps like I used in the 70's for machine control design, and get a really big rotary switch. My head hurts already just thinking about it. 
Title: Re: 3-phase power demonstration
Post by: Jay Barracato on December 11, 2018, 02:52:19 pm
This really is too much fun!

Now what I need to consider is how to take the three transformer secondaries and rewire them as WYE, Delta or High-Leg Delta services at the flip of a switch. I'm not sure I trust myself to use banana plugs to rewire the various configurations while simultaneously teaching a seminar. Of course I could do the Rick Wakeman brute force method and have 9 transformers feeding 3 different service panels with everything wired at once, but that seems like cheating and too heavy to take on a plane. Looks like I need to remember Boolean Algebra and Karnaugh maps like I used in the 70's for machine control design, and get a really big rotary switch. My head hurts already just thinking about it.
I think switches up is wye, switches down is Delta for the primaries. I am not sure how you were going to do the tap.(https://uploads.tapatalk-cdn.com/20181211/092370daef8f2215ddc8ab588f97a666.jpg)

Sent from my Moto Z (2) using Tapatalk

Title: Re: 3-phase power demonstration
Post by: Mike Sokol on December 11, 2018, 04:06:03 pm
Just finished talking to a very knowledgeable field engineer for Harman/Crown, and he thinks the CT475 amplifier should do the job. But in the discussion we began talking about using a London Blu-50 DSP processor to generate the 3-phase 60-Hz signal. I have a fair amount of experience with London Blu programming, so building a 3-phase signal generator in the DSP should be really simple. Lot's of ways to do this thing, and all of them really cool.

So much technology, so little time....   
Title: Re: 3-phase power demonstration
Post by: Tim McCulloch on December 11, 2018, 04:45:54 pm
Just finished talking to a very knowledgeable field engineer for Harman/Crown, and he thinks the CT475 amplifier should do the job. But in the discussion we began talking about using a London Blu-50 DSP processor to generate the 3-phase 60-Hz signal. I have a fair amount of experience with London Blu programming, so building a 3-phase signal generator in the DSP should be really simple. Lot's of ways to do this thing, and all of them really cool.

So much technology, so little time....   

I'm seeing some real value in the DSP approach but the Dr. Frankenstein in me wants big copper knife switches and some high voltage discharge toys.  Oh, you said you have to fly this on commercial aircraft?  Never mind.

Hmmm... Lights and loudspeakers, too?  You can demonstrate the audibility of phase when adding 120° and 240°, and then with "split, single phase".  Two birds or too confusing?

This is for an AV company, training their techs to measure, recognize and understand some of the theory behind 3 phase?  I'd mostly emphasize the things they're likely to encounter in their typical venues and work.  Delta and high-leg delta probably exist in some of this company's locations but for the most part will never be encountered directly by an AV tech; usually a building engineer or house electrician takes care of things not plug 'n play.  That said, I've see what passes for in-house distro boards and misuse of outlets and plugs meant for other services to prevent clients from plugging in without being billed.  If this is for their techs doing special event one offs I think there would be a whole lot more than you can cover in 8 hours.... which is my segue to:

The ETCP portable power certification test.
https://etcp.esta.org/certify/examination_ppdt.html

There is also the companion (and more theatrically oriented)
https://etcp.esta.org/certify/examination_electrical.html

Title: Re: 3-phase power demonstration
Post by: Mike Sokol on December 11, 2018, 06:40:43 pm

This is for an AV company, training their techs to measure, recognize and understand some of the theory behind 3 phase?  I'd mostly emphasize the things they're likely to encounter in their typical venues and work.  Delta and high-leg delta probably exist in some of this company's locations but for the most part will never be encountered directly by an AV tech; usually a building engineer or house electrician takes care of things not plug 'n play. 

The ETCP portable power certification test.
https://etcp.esta.org/certify/examination_ppdt.html

There is also the companion (and more theatrically oriented)
https://etcp.esta.org/certify/examination_electrical.html

Their training manager specifically asked for a class on how to measure power systems and recognize Delta, WYE, High-Leg-Delta, and Split-Phase 120/240. Perhaps they got tied into a High-Leg-Delta feed at some point in time and dumped 208 volts into a bunch of 120-volt only gear.

I've seen some really wacky wiring at hotel conference rooms and wineries. For instance I found a 4-wire/3-phase/240-volt Delta (3 hots and a ground without a neutral) receptacle at a pretty new winery recently. The house tech said I could plug in there, but I took one look at the receptacle and pulled out my meter to confirm that was a non-starter. I just put my Honda EU3000i genny around the corner of the building and ran my 100 ft of 6/4 back to the distro. Everybody much happier... 

I also found the distro split from hell at a conference center that was a 3-wire/50-amp/240-volt welder plug split out to a bunch of Edison outlets. Again, no real neutral, just a small EGC/Ground wire. I opted for running a few long extension cords over to wall mounted Edison outlets that tested OK with my SureTest Analyzer.   
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on December 11, 2018, 07:09:47 pm
More crazy Wild-Leg-Delta encounters. I've found this sort of 3-phase service panel in a few churches that were converted warehouse factories. Of course, High or Wild-Leg-Delta power is really common in factories that needed to power a bunch of 3-phase/240-volt motors, and only needed limited amounts of split phase 120/240-volt power for the offices. But DIY church handymen being who they are, I've found some really strange and dangerous wiring. I don't trust anybody's wiring any more, especially when it's a brand new receptacle in a very old church.  Take a look at this receptacle in a shop that totally confused the electrician who installed it. Here's a link to the entire thread: https://diy.stackexchange.com/questions/109837/240v-outlet-with-120v-and-215v-how/109840

Title: Re: 3-phase power demonstration
Post by: Tim McCulloch on December 11, 2018, 07:20:43 pm
I don't doubt what you find, in fact my previous reply was much longer (edited down before I hit send) with some stories about what I've found in hotels and convention centers and why they do it (revenue).

I guess I'd rather have line technicians trained to find out that something is wrong and have their employer fix it, than have employees who try to fix/modify/engineer a kludge.

Title: Re: 3-phase power demonstration
Post by: Mike Sokol on December 11, 2018, 08:26:17 pm
I guess I'd rather have line technicians trained to find out that something is wrong and have their employer fix it, than have employees who try to fix/modify/engineer a kludge.
I don't plan to teach these guys/gals how to fix or modify any wiring, only to recognize what's safe and what's dangerous.
Title: Re: 3-phase power demonstration
Post by: Tim McCulloch on December 12, 2018, 01:13:00 am
I don't plan to teach these guys/gals how to fix or modify any wiring, only to recognize what's safe and what's dangerous.

We're on the same page.  Carry on!

You could really geek out the demo with DSP, though.   8)
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on December 12, 2018, 07:00:34 am
You could really geek out the demo with DSP, though.   8)

Yeah, the tech support guy I talked to at Harman was really excited about the DSP application. In addition to standard 3-phase/120-degree service, it would also be simple to create 2-phase/90-degree power (of course, obsolete now) and wire up a Scott-T transformer to show 2-phase to 3-phase conversion. That would be a real hoot!
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on December 12, 2018, 07:43:31 am
You need to add an islated neutral bus to do this right.-as it is pictued that panel is only acceptable for delta connected loads.

This looks like a better choice for a load center since it already has an isolated neutral, ground bar, and all the other fixin's. I'll just add a few 2-pole and 3-pole circuit breakers and it's ready to demo 3P power. 
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on December 12, 2018, 07:54:56 am
Once I commit to a 75-watt class amplifier, then 24-volt HVAC transformers with a 120/240-volt primary are really common. This one is 40VA which should match up very nicely with the amplifier. Cost is only $18 ea with shipping, so super-cheap. I'll need four of them since I'm going to hook up the 4th amplifier channel for who-knows-what. Perhaps it could drive a second service panel to demonstrate 1P 120/240-volt power.
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on December 13, 2018, 05:14:54 pm
This could be a start. I found a tiny 3-phase "alternator" that's used to demonstrate wind generator theory. I think it will output around 24 volts at 1,800 RPM, but who knows. I'm going to spin it with a little 1,800 RPM shaded pole fan motor. Yes, I know a shaded pole motor is not synchronous (like a Hammond B3 tone generator) and will slip a bit under load. But even if it ends up at 59 Hz that's good enough for a start. In any event I ordered one since at $8 with shipping it's cheap enough to throw away, and will a good test of my training protocol.
Title: Re: 3-phase power demonstration
Post by: Stephen Swaffer on December 13, 2018, 07:53:50 pm
So, motors have a lot in common with transformers.  An older semi-obsolete motor starting method is Wye-Delta start.  You supply 3 phase, and a set of contactors supplies power to the motor in a Wye configuration, then a timer switches contactors and motor switches to a delta run.  I'm thinking that hooking transformers up where the motor is and manually controlling the switching should allow you to hook up either a wye or delta supply going "backwards" through the relay.  I don't have a schematic handy but will check one out tomorrow.
Title: Re: 3-phase power demonstration
Post by: Frank Koenig on December 14, 2018, 12:46:33 am
This could be a start. I found a tiny 3-phase "alternator" that's used to demonstrate wind generator theory. I think it will output around 24 volts at 1,800 RPM, but who knows. I'm going to spin it with a little 1,800 RPM shaded pole fan motor. Yes, I know a shaded pole motor is not synchronous (like a Hammond B3 tone generator) and will slip a bit under load. But even if it ends up at 59 Hz that's good enough for a start. In any event I ordered one since at $8 with shipping it's cheap enough to throw away, and will a good test of my training protocol.

It will make 60 Hz at 1800 RPM only if it has four poles per phase.  This one looks like it a total of 9 windings, so I'm not sure. I guess all I'm saying is you might need some other speed than 1800 RPM.
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on December 14, 2018, 06:27:50 am
It will make 60 Hz at 1800 RPM only if it has four poles per phase.  This one looks like it a total of 9 windings, so I'm not sure. I guess all I'm saying is you might need some other speed than 1800 RPM.

Yeah, I was trying to count poles and figure out the geometry. The specifications say it has 3 output wires, so it's probably connected up delta. Of course I could use a little variable speed DC motor to spin it at the correct speed, or a small pulley set to change the speed. But it will be easy to figure out once I can spin it. Now all I need is a 4-trace oscilloscope for these experiments. 
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on December 14, 2018, 07:12:57 am
I'm now thinking about what I actucally need to demonstrate live in class. While it would be good to show a slide of how delta is converted to wye, and I could probably put test points on this gadget to show primary 3-wire delta voltages, I don't think anyone other than a POCO lineman would ever encounter 3-wire delta. So I think I need a 3-phase load center that I can switch between Wye 208/120 and High-Leg, 4-wire Delta 240/120. Then I could bring a small single phase load center to demonstrate single phase 240/120-volt wiring. For that 1p panel I could use a small 120/240-volt CT transformer fed from my B&K variable AC power supply to demonstrate low and high voltages.

One of the reasons I want some reasonable available load current is I want to demonstrate what you'll see when an undersized neutral is in a system. I first encountered this phenomenon at the Old Mill Inn some 40+ years ago when I noticed that when we fired up 50KW worth of PAR lighting on one of the panel legs, the voltage would drop down to maybe 110 volts, while the voltage on the other unloaded leg in the panel would rise to 130 volts or so. The only reasonable explanation was the neural couldn't support the current unbalance without a significant voltage drop.

Of course I had my lighting tech turn banks of our PAR lights on and off while I measured voltages in the open electrical panel. Not something I recommend to unqualified personnel, but I already had my Master Electrician license at the time and was taking classes for an EE degree, so it was a interesting live experiment.   
Title: Re: 3-phase power demonstration
Post by: Tom Bourke on December 14, 2018, 10:09:13 am
I'm now thinking about what I actucally need to demonstrate live in class. While it would be good to show a slide of how delta is converted to wye, and I could probably put test points on this gadget to show primary 3-wire delta voltages, I don't think anyone other than a POCO lineman would ever encounter 3-wire delta. So I think I need a 3-phase load center that I can switch between Wye 208/120 and High-Leg, 4-wire Delta 240/120. Then I could bring a small single phase load center to demonstrate single phase 240/120-volt wiring. For that 1p panel I could use a small 120/240-volt CT transformer fed from my B&K variable AC power supply to demonstrate low and high voltages.
Having tried to teach complex concepts to simple AV techs, I feel your pain.  In my case most just wanted a recipe to make it work.  For power I would not make the test rig they deal with to complex.  A selection of the outlets they will have to deal with and what they should read.  Some instruction on the NEMA numbers and how to read a chart of connectors.

Having said that, here in Vegas we have mostly modern 120/208 Y or maybe 277/480.  Most venues have a maintenance department.  Mostly just need to make sure the connectors are wired right and the screws tight.  Other parts of the country and world don't have it so nice.  I have seen some strange in some of the old converted factory and mills in older towns.  Corner grounded Delta any one?  How about buck/boost transformers.  They don't need to understand how it works, just that it's not good for them to plug into.
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on December 14, 2018, 05:34:26 pm
Corner grounded Delta any one?

I've never seen one of these in the wild, so I'm considering whether or not to include a corner ground Delta in this seminar. At least I could put up a ppt slide showing how it will measure, but not spend any time on a live demonstration.

I was planning to include handouts with all the possible NEMA connectors as well as CEE-Form and Camlok color coding for various countries. Lots to do.   
Title: Re: 3-phase power demonstration
Post by: Jonathan Johnson on December 14, 2018, 11:21:46 pm
Is there a difference between high leg delta and wild leg delta?

High leg delta is what we think it is. Wild leg delta is the same as high leg, except that only two transformers are used? Or is that the "corner ground" just mentioned?
Title: Re: 3-phase power demonstration
Post by: Stephen Swaffer on December 14, 2018, 11:58:06 pm
I would tend to agree that ow the transformers are wired is less important than how to measure-and really the big thing is are they dealing with 4 wire 3 phase, or just 3 wire (not counting equipment ground).

In the facility I work in, there are 3 phase/4 wire panels-ones that I can run 277 volt lights from, and there are a number of 3 phase/3 wire panels that can only be used for 3 phase loads-or maybe single phase line-line or 480 V.  They are all supplied from the same transformer.  You can feed a 3 phase delta primary transformer and get a 3 phase/4 wire 208/120 panel, if needed.

It would not surprise me to see a large subpanel feeding only 3 phase HVAC loads in a commercial building that did not have a neutral installed in the panel.  But, in the interests of having a grounded system, that panel will most often be fed with a wye connected transformer (at least in any newer install in most of North

Of course, identifying a wild leg or corner grounded would be important-but those are just voltage measurements.
Title: Re: 3-phase power demonstration
Post by: Tom Bourke on December 15, 2018, 12:45:07 am
Is there a difference between high leg delta and wild leg delta?

High leg delta is what we think it is. Wild leg delta is the same as high leg, except that only two transformers are used? Or is that the "corner ground" just mentioned?
Wild and high leg delta are the same as far as I know.  A delta connection of 3 240V coils with one being center tapped and that center tap bonded with ground.  The high leg is about 208V to neutral. Since the high leg is not direct referenced by a bond or single coil to ground it can vary widely, with respect to ground, depending on loads.  That is where the "wild" comes from.

The 2 transformer delta V configuration is used where the power company wants to save on transformers yet have the ability to upgrade.  From an end user stand point it should not matter unless you draw more that the POCO provisioned.

Corner grounded delta is where one of the 3 hot legs is also bonded to ground.  Mutually exclusive with high leg delta and Y configurations.  You can almost treat it like split/single phase, other that the voltages being off.  I have only personally measured it in an old building at a very old elevator control panel.  I have also heard about situations using it for non motor loads causing catastrophic inductive heating  in the conduit.

Buck/ boost transformers can take a 277 and drop it to 240 or take 208 and boost it to 240.  And then is it 240 or 220 the person was looking for?  110 or 120 or 125?  To hook my single phase 230 volt air compressor to 208 three phase I have a buck/boost transformer.

That's the real complexity of measuring electrical systems.  An industrial situation is very different from an AV situation.  Add on a situation with some one who knows just enough to be dangerous?

My point about go/nogo measurements is based on how you get the voltage your seeing.  When you factor in +-10%  variance and allowed drop , it can get very confusing. 
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on December 15, 2018, 10:49:16 am
That's the real complexity of measuring electrical systems.  An industrial situation is very different from an AV situation.  Add on a situation with some one who knows just enough to be dangerous?

My plan is to teach these AVL technicians how to recognize various transformer configurations and know what's safe and what to avoid. I've done enough shows at big hotel conference rooms where the facility guy shows me where to hook up power and says that "everyone" uses some really sketchy looking receptacle. I've learned not to trust anyone until I measure it myself.

This is especially true with new churches that have moved into old industrial warehouses, many of which have 3-phase, high-leg Delta panels. The other thing to be aware of is that even the ones with 4-wire WYE transformers often have undersized neutrals since much of the original industrial load was 3-phase motors. The undersized neutrals can easily be overloaded when you hook tungsten dimmer packs on a single phase, which can create odd-order triplen currents on the neutral.

I'm not sure how many residential electricians (even licensed ones) would recognize all these flavors of 3-phase power since they would probably never encounter them in a non-industrial situation. But 3-phase power can be dangerous if you don't know what you're doing. Much to teach about.   
Title: Re: 3-phase power demonstration
Post by: Tim McCulloch on December 15, 2018, 12:43:51 pm
My plan is to teach these AVL technicians how to recognize various transformer configurations and know what's safe and what to avoid. I've done enough shows at big hotel conference rooms where the facility guy shows me where to hook up power and says that "everyone" uses some really sketchy looking receptacle. I've learned not to trust anyone until I measure it myself.

This is especially true with new churches that have moved into old industrial warehouses, many of which have 3-phase, high-leg Delta panels. The other thing to be aware of is that even the ones with 4-wire WYE transformers often have undersized neutrals since much of the original industrial load was 3-phase motors. The undersized neutrals can easily be overloaded when you hook tungsten dimmer packs on a single phase, which can create odd-order triplen currents on the neutral.

I'm not sure how many residential electricians (even licensed ones) would recognize all these flavors of 3-phase power since they would probably never encounter them in a non-industrial situation. But 3-phase power can be dangerous if you don't know what you're doing. Much to teach about.

I think it's very possible to try and teach too much to lowest tier hotel AV techs.  I think I'd start with a "go/no-go" module and then delve into theory after lunch for those still interested.

The very first post in this forum is about a hotel meeting room with an Edison power outlet that's labeled "microphone."  I don't expect hotels to do much better.  I agree that meter everything is best practice and one I use, but even at my level of interaction I don't care if a service is 480v delta or 208/277 high leg or 120/208/240 if I don't get the correct meter readings.  I can't change it - my only recourse is to not use it and get someone from the hotel or convention center to label it.

Again I'm all for knowledge (except for forums run by Social Knowledge, but that's another matter) but I think this needs to focus on safety of personnel, guests and equipment.  The *theory* behind 'unsafe for our use' services is nice but unnecessary for most AV techs.  All that is necessary is for techs to recognize over voltage and not use it.

This all said, I'm guessing there is a story or 2 behind this request.  Can you share?
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on December 15, 2018, 06:20:21 pm
This all said, I'm guessing there is a story or 2 behind this request.  Can you share?
I've not spoke at length to their head tech guy yet, so I don't have any intel as to what caused this line of inquiry. We're supposed to talk on Monday, so that's going to be my main line of questioning. What kind of power situations do they find themselves in, and was there some specific incident that went sideways? Right now I just have a bullet list of topics to cover, so I do need to know spin and depth of my training class. But as you said, many times you just need to give technicians a go/no-go type of SOP.
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on December 15, 2018, 06:30:12 pm
Check this out. I found a 3-phase signal generator from China for $31.88 with shipping. Signal level appears to be 5 volt P-P which would drive any small power amp nicely. https://www.ebay.com/itm/1-00-200KHZ-3-Phase-Sine-Signal-Generator-0-to-360-Frequency-meter-Counter-/172793617133?_trksid=p2349526.m4383.l4275.c10#viTabs_0

Circling back to the top of the thread, adding a pair of the Lepai 2020 amplifiers at $20 each might be the best choice for a voltage-only 3-phase demonstration. And these little transformers could get the voltage swing up to 120/240-volts as well as Delta or WYE configurations. 

If this works (and I'm reasonably sure it will), then it's certainly cheap enough, small enough and simple enough for a tabletop demonstration.
Title: Re: 3-phase power demonstration
Post by: Stephen Swaffer on December 15, 2018, 10:39:23 pm
I think it's very possible to try and teach too much to lowest tier hotel AV techs.  I think I'd start with a "go/no-go" module and then delve into theory after lunch for those still interested.

The very first post in this forum is about a hotel meeting room with an Edison power outlet that's labeled "microphone."  I don't expect hotels to do much better.  I agree that meter everything is best practice and one I use, but even at my level of interaction I don't care if a service is 480v delta or 208/277 high leg or 120/208/240 if I don't get the correct meter readings.  I can't change it - my only recourse is to not use it and get someone from the hotel or convention center to label it.

Again I'm all for knowledge (except for forums run by Social Knowledge, but that's another matter) but I think this needs to focus on safety of personnel, guests and equipment.  The *theory* behind 'unsafe for our use' services is nice but unnecessary for most AV techs. All that is necessary is for techs to recognize over voltage and not use it.

This all said, I'm guessing there is a story or 2 behind this request.  Can you share?

I would disagree to an extent.  I realize my background is industrial-but there is no technical reason not to install a 3 phase load only panel in a commercial facility to supply HVAC loads, etc.  The first 3 phase panel Mike showed was designed for such a use-no isolated neutral bus.  A panel like this will have the correct voltage readings-but on a 200 amp panel the difference between a properly sized grounding conductor and a properly sized grounded (aka neutral) conductor is from a #6 to a 3/0.  Similarly a 3 phase receptacle with a grounding conductor but no neutral would be likely to have too small a conductor to run single phase loads.

This "hack"-using a grounding conductor as a neutral is a code violation and a very real safety issue-and it is one of the most common ones I see (short of ignoring the importance of the grounding conductor/safety ground).

In my opinion, knowing how to check voltages is critical-as is determining if a 3 phase power source is a legitimate source of single phase power.  The "wye"-"delta" determination Mike originally mentioned-but the critical thing is if the 4th wire of the "wye" is available at the panel/receptacle-not necessarily if the transformer is delta connected.
Title: Re: 3-phase power demonstration
Post by: Tim McCulloch on December 16, 2018, 12:23:01 pm
I would disagree to an extent.  I realize my background is industrial-but there is no technical reason not to install a 3 phase load only panel in a commercial facility to supply HVAC loads, etc.  The first 3 phase panel Mike showed was designed for such a use-no isolated neutral bus.  A panel like this will have the correct voltage readings-but on a 200 amp panel the difference between a properly sized grounding conductor and a properly sized grounded (aka neutral) conductor is from a #6 to a 3/0.  Similarly a 3 phase receptacle with a grounding conductor but no neutral would be likely to have too small a conductor to run single phase loads.

This "hack"-using a grounding conductor as a neutral is a code violation and a very real safety issue-and it is one of the most common ones I see (short of ignoring the importance of the grounding conductor/safety ground).

In my opinion, knowing how to check voltages is critical-as is determining if a 3 phase power source is a legitimate source of single phase power.  The "wye"-"delta" determination Mike originally mentioned-but the critical thing is if the 4th wire of the "wye" is available at the panel/receptacle-not necessarily if the transformer is delta connected.

AV technicians will not be dealing with any source of power that doesn't come from some kind of NEMA outlet (whether or not it's the right outlet for the service is another matter).  They won't be poking around in panels or wiring outlets.  It is not necessary for them to understand 'why' an outlet doesn't meter correctly, only that it does not.  In a hotel or convention center the responsibility to make it right is with the engineering or maintenance dept. or they will call this electrician from Iowa... ;)

Again, I think imparting solid, foundational knowledge is good thing in general.  What I'm doubting is that AV techs working mostly in the same venue, same meeting rooms and ball rooms will *need* to understand the theory nearly as much as knowing they're on the wrong service.

For technicians working in unfamiliar facilities, again knowing that they shouldn't use a particular outlet or service disconnect when it "meters funny" is more important than their being able to identify the nature of the errant service.

Title: Re: 3-phase power demonstration
Post by: Frank Koenig on December 16, 2018, 12:44:50 pm
From having read all the above it sounds like a really good thing for these AV techs, and maybe for the rest of us as well, would be a nice, durable pocket chart that has illustrations of all the NEMA receptacles they're likely to encounter along with the expected meter readings. It would also call out receptacles that are unsuitable for Y-connection for lack of a neutral, as well as the now deprecated 3-wire home range and dryer receptacles.

The rule is if it doesn't meter as expected, don't use it, and enquire.

--Frank   
Title: Re: 3-phase power demonstration
Post by: Stephen Swaffer on December 16, 2018, 03:57:10 pm
AV technicians will not be dealing with any source of power that doesn't come from some kind of NEMA outlet (whether or not it's the right outlet for the service is another matter).  They won't be poking around in panels or wiring outlets.  It is not necessary for them to understand 'why' an outlet doesn't meter correctly, only that it does not.  In a hotel or convention center the responsibility to make it right is with the engineering or maintenance dept. or they will call this electrician from Iowa... ;)



Mike's OP indicated they wanted him to teach how to recognize transformer connections, etc.  That leads me to assume  :o  that somehow they had an issue and whoever was involved was doing more than plugging a NEMA plug into a NEMA receptacle.

Frank's suggestion seems to be a good one.  There are plenty of reference charts out there-but one edited for AV techs or even better one for "these are acceptable receptacles for our feeders or gear" might be even better.
Title: Re: 3-phase power demonstration
Post by: Tim McCulloch on December 16, 2018, 04:23:18 pm
Mike's OP indicated they wanted him to teach how to recognize transformer connections, etc.  That leads me to assume  :o  that somehow they had an issue and whoever was involved was doing more than plugging a NEMA plug into a NEMA receptacle.


That's why I'm waiting for the back story on this.  For hotel or convention center work NO AV tech is working inside a panel, ever.  At the hotels we work in the only services accessible to line staff are on some kind of outlets (including CamLocks, but then the switch has to be unlocked by a building engineer).

Hell, we can't even have ETCP-certified electricians tap tails into company switch lugs at the PAC, a city employee electrician has to do it.  Not because there was an issue (ever, in the 20 years I've worked in the venue) but because a non-electrician city worker was replacing a light switch and didn't test for power down.  No injury, no property damage, but the venue manager had a hissy fit and penalized the people trained and certified to do their jobs on stage.

Kansas isn't a bastion of progressive thinking (if they could eliminate workman's comp they would) so I don't think I'm in Nanny State.  I've worked in places with scary wiring, bogus "distro boards" and all kinds of non-compliant wiring but that wiring wasn't used with outside products (in house distros only, those kind of things).

My concern over trying to instill too much info is that the trainee's brains shut down and they absorb nothing, rather than taking away the parts about preventing electrical fires and not killing people through rejection of non-conforming outlets.
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on December 17, 2018, 12:01:48 am
My concern over trying to instill too much info is that the trainee's brains shut down and they absorb nothing, rather than taking away the parts about preventing electrical fires and not killing people through rejection of non-conforming outlets.

It's tricky to find the sweet spot between presenting too little info, and information overload. But reading between the lines it feels like something weird must have happened involving 3-phase power. In addition to a list of typical wiring situations they find themselves in, I'm also going to suggest doing a pre-seminar phone conference with a few of the trainees to try and determine just how much they already know. Could be a little... Could be a lot...

I suspect there's a certain stratification of technical levels, with some newbies needing to know the basics of how to test a stage for back-line stray voltages using a NCVT, and some veterans needing to understand power factor and how triplen harmonic currents can overload neutrals. Of course, there probably will be many techs in between these levels. They've also asked for a possible advanced training class in a few months, so I just don't know enough details yet to create a syllabus, but this sure is interesting. Once I get more info on their current technical level and the type of gigs they typically do, I'll be better able to focus on actual training content.   

Of course, I'm sharing this information with you so you can all mentally play along with the process of developing a training seminar. Personally, I've found that the process of preparing to teach a topic has made me a much better engineer over the years. And you guys are great at helping me come up with training ideas, so your input is very much appreciated. Stay tuned as I learn more.     
Title: Re: 3-phase power demonstration
Post by: Chris Hindle on December 17, 2018, 08:42:21 am
Mike, I'm leaning towards a 3-step program.

Step 1, assume they know nothing - or what they do know is hearsay.
An introductory to get them comfortable with AC in general, and on-site testing and verification for human and equipment safety in mind.

Step 2, go into WHY they see what they may face in measuring.
To many of them, this will be an abstract. Plasticized "memory cards" will be worth their weight in gold, down the road.

Step 3, yearly "refresher" courses ?

In my humble opinion, schooling is fairly useless if you don't run into the scenarios yourself. Hopefully, these guys will never see some of the situations you will describe, but they NEED to understand completely what the multimeters are telling them.

Pretty sure a rig got torched, and that's why you were contacted.

Just my 2 cents, of course.
Chris.
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on December 20, 2018, 12:35:59 pm
I have confirmation on the training gig, and have a month to put it all together. As suspected, there are seasoned tech guys with many years in the touring business, down to brand new greenhorns, and lots of crew in between. And their normal gigs include large tours, hotel ballroom events, outdoor festivals on generator power, and small one-off local and political gigs. Nobody wants to admit to setting a rig on fire, but we all know how that one goes.  ;)

Per my conversation with their tech director, the touring gigs are usually pretty straightforward since these are mostly union houses and everyone knows how to play together. But their touring guys would like a better understanding of what's under the hood when it comes to 3-phase power. He likes the idea of a connector chart showing acceptable voltages and such. Plus he said specifically that they need to know how to identify an undersized neutral under load. Triplen currents and power factor would be an advanced course out in the future. Fair enough.

The hotel ballroom gigs are a veritable plethora of crazy power situations, and their intermediate tech guys need to know how various receptacles and house distro power should measure, and what to stay away from.

The outside festivals generally supply their own generators, which can be hit or miss. So I need to include basic generator connections and measurements, along with best practices for generator grounding and stage bonding. Got it.

And the one-off political gigs might be outside and need a small inverter generator, or happen in a school cafeteria or the town console office. So they need to know how to use a small Honda generator or to properly measure and qualify a plain old Edison outlet in a gymnasium.

I can do this in two training seminars, with the first class next month covering all the measurement basics including how to use a DMM, clamp-ampmeter, Ground impedance tester, etc.  A few months later I could follow up with an advanced class, and after that do a yearly refresher course for the new crew members, etc...

So at least I have the basics and they've approved the syllabus I've already sent them. As usual, the knowledge of how this all works is pretty straightforward for many of you on this forum. The real trick is how to package it into bite-sized pieces that nobody chokes on. Lots of work to do on this one. 
Title: Re: 3-phase power demonstration
Post by: Tim McCulloch on December 20, 2018, 12:46:36 pm
Mike, did you look over the ETCP electrician and portable power certifications?

Edit ps: in the "Last Post" column on the index page the topic shows up as "3-phase power demons..."
Title: Re: 3-phase power demonstration
Post by: Chris Hindle on December 20, 2018, 01:18:00 pm
Edit ps: in the "Last Post" column on the index page the topic shows up as "3-phase power demons..."
Well, do it wrong, and the "description" is not far off.....
You can get bit pretty hard...
Chris.
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on December 20, 2018, 02:09:48 pm
Mike, did you look over the ETCP electrician and portable power certifications?

Edit ps: in the "Last Post" column on the index page the topic shows up as "3-phase power demons..."

Yes, I did. And that could be a great resource for their advanced techs.
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on December 21, 2018, 07:43:06 am
Figured I'd risk $23 (shipping included) on a 4-channel "400-watt" car amplifier to power this rig. Looks simple enough without any crossovers or fancy connectors. Just RCA inputs and Screw Terminal outputs.

I think the output voltage swing will match up nicely with the 6.3/12.6-volt filament transformers from Hammond. I ordered the transformers through Allied a few days ago, and their Columbia, MD field office called me wondering what I was doing with them. When I explained they thought it was really cool. I should bring this rig to AES sometime for a show & tell. 

Everything should be here in time for Christmas, so I know what I'll be doing in the afternoon after all the relatives have gone. Or sometimes I retreat to my lab in the morning while family and visitors are still here. None of you guys ever do that, do you??? ;)

 
Title: Re: 3-phase power demonstration
Post by: Curt Sorensen on December 21, 2018, 01:30:17 pm
Hi,

If there's any chance of such a presentation to be recorded, streamed, or shared somehow, that would be quite valuable to me and I'm sure many  others. Understood there may be reasons it can't happen.

Thanks for all y'all contribute,
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on December 21, 2018, 01:50:50 pm
Hi,

If there's any chance of such a presentation to be recorded, streamed, or shared somehow, that would be quite valuable to me and I'm sure many  others. Understood there may be reasons it can't happen.

Thanks for all y'all contribute

I won’t be able to stream this particular seminar due to privacy and copyright issues, but I’m working on a way to publish this content in 10-minute videos. Stay tuned.
Title: Re: 3-phase power demonstration
Post by: Dave Garoutte on December 21, 2018, 03:53:24 pm
I won’t be able to stream this particular seminar due to privacy and copyright issues, but I’m working on a way to publish this content in 10-minute videos. Stay tuned.
Very interested.
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on December 26, 2018, 06:25:33 pm
The 4-channel amp as well as the 12.6-volt transformers have arrived, but the 3-phase signal generator won't be here for another week at least (slow boat from China, literally). But I can use a 60-Hz sine wave on my phone to drive the amps, and my trusty O'scope to check out the waveform on the "primary" 115/230-volt side of the transformers. If that works as envisioned, then I'm going to mount everything on a backing plate that will fit in a Pelican case for transport.   
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on December 30, 2018, 10:33:56 am
Here's the single-phase version of the demonstration rig. The little "400-watt" car amp makes around 8 volts RMS output without clipping, so I used the 6.3-volt secondary of the transformer. This easily makes 120/240-volts on the transformer primary which is actually my secondary.

I'm using a HOSA 1500mA 12-volt universal power supply to run this mess, but that could be a little light when I get all 4 channels up and running, so I'll upgrade it to a 5000mA 12-volt DC supply just so it doesn't die if an output of the amplifier gets shorted. But this is all very current limited so I shouldn't have any fireballs if something goes wrong.

Still waiting on my 3-phase signal generator from China, which hopefully will arrive this week. In the meantime I'm going to mount this down on a little board that will fit in a pelican case and wire it up all pretty with appropriate test points. Everything looks like it's going to work, so I'm a happy guy so far.

I've got to bring this demonstration to AES for show and tell.
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on December 30, 2018, 04:19:07 pm
Just ordered this 12-volt/30-amp regulated supply from Amazon for $19 with shipping. The 400-watt car amplifier has a 15-amp fuse, so this power supply should be able to supply sufficient current for worst case shorting scenarios without shutting down. It will be here on Wednesday.
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on December 31, 2018, 08:26:07 am
So here's what I'm thinking about doing to demonstrate wiring of various 3-phase configurations. I was going to mount this on a piece of plywood, but my wife gave me an old white-board yesterday, so I started laying out how to mount the transformers on it. Then I drew out where I could mount 5-way binding posts for various connections and test points. After I did that with dry-erase markers it hit me. Why don't I just mount the transformers and 5-way binding posts on the whiteboard and put a hinge on the bottom so it can lay flat for transport or an overhead video camera, and it can flip up at an angle for direct viewing and testing by the class. I can literally sketch the various diagrams for standard Delta, Grounded-Leg Delta, High-Leg Delta, 3-leg WYI, 2-leg WYI and whatever else comes to mind (open leg Delta, perhaps?) right on the white-board, then hook it up using colored banana plugs. I can get 5-way binding posts in Black, Red, Blue, Green and Yellow (no white that I can find, but maybe yellow is OK), and get banana plug jumpers in these colors as well.

So what do you think? Is this a good way to bring a schematic on paper to life? As I've noted earlier, this system does make actual 120/208/240 volts AC at maybe 100mA current per leg, so students can use their own meters set to real scales for measurements.

As a side note, I'm installing a GFCI plug on the incoming 120-volt AC power cord feeding this entire rig, so that if someone accidentally gets between a hot test point and anything grounded the GFCI will trip before it electrocutes them. It would be a little embarrassing to kill someone in my seminar while trying to demonstrate electrical testing and safety.  ::) 
Title: Re: 3-phase power demonstration
Post by: Stephen Swaffer on December 31, 2018, 12:51:22 pm
I like the white board idea-might steal it myself!

The GFCI is not a bad precaution-but you are already using transformers.  For the purpose of this demo, they probably need to be un-bonded so actually true isolation transformers.  Isolation transformers are a reasonable and common safety precaution often used on test benches-but if someone manages to get "bit" by one it will still present a balanced hot/neutral current to the GFCI.
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on December 31, 2018, 01:13:29 pm
I like the white board idea-might steal it myself!

The GFCI is not a bad precaution-but you are already using transformers.  For the purpose of this demo, they probably need to be un-bonded so actually true isolation transformers.  Isolation transformers are a reasonable and common safety precaution often used on test benches-but if someone manages to get "bit" by one it will still present a balanced hot/neutral current to the GFCI.

My plan is to create a bonded-ground system, just like the real thing. So the neutral of the transformer secondaries will be bonded to the incoming EGC from the wall receptacle. That's because I want to be able to demonstrate NCVT testing with this setup, and should be able to recreate a null/center position near the center of the transformers, that will cancel out a NCVT response. At least, that's what I've been told by a few old-timer electricians who don't trust NCVTs. Of course, I only trust them a little after I verify that they're actually working, and I would never use one as the ONLY way to verify that power was off in big panel or machine. But they're just one more layer of testing. 
Title: Re: 3-phase power demonstration
Post by: Dave Garoutte on December 31, 2018, 02:14:16 pm
As you were describing it, I'm thinking, 'why not just use the white board?'.  five words later you read my mind. ::)
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on December 31, 2018, 02:29:14 pm
As you were describing it, I'm thinking, 'why not just use the white board?'.  five words later you read my mind. ::)

Hey, great minds think alike, or whatever.  ;D

I think there's a teaching advantage to laying out a circuit that resembles its schematic counterpart. This transformer-triangle is how I tend to think about 3-phase power inside of my head, especially for high-leg or grounded-leg Delta service. And it works well enough for 120/208 WYE service as well. All easy to demonstrate schematically and literally with a few colored dry markers and jumper plugs on my white board.
 

Title: Re: 3-phase power demonstration
Post by: Mike Sokol on December 31, 2018, 02:55:33 pm
The GFCI is not a bad precaution-but you are already using transformers.  For the purpose of this demo, they probably need to be un-bonded so actually true isolation transformers.  Isolation transformers are a reasonable and common safety precaution often used on test benches-but if someone manages to get "bit" by one it will still present a balanced hot/neutral current to the GFCI.

I would be really worried about an untrained consumer getting across two hot-legs of this this thing, but in this particular seminar I'm teaching AVL technicians what to look for when measuring power in a venue, which they already do all the time with their own meters. Plus I'll be sitting right in front of them watching like a hawk for any bad practices, like laying one hand on the transformers and the other on the meter probe. Come to think of it, I could choose not to ground the transformer shell allowing them to float. As long as they didn't leak too much internally that could offer an extra layer of safety. What do you all think?
Title: Re: 3-phase power demonstration
Post by: Stephen Swaffer on December 31, 2018, 03:43:16 pm
I think I would bond the shells together so they stay at the same potential-a neon light connected between them and ground would be a super safe way just in case they became energized through a fault.  Should be safe enough as long as the whole contraption is GFCI protected.

I guess I assumed you would not always have a bonded neutral to work with-if you wire and demo a true delta.
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on December 31, 2018, 04:57:01 pm
I think I would bond the shells together so they stay at the same potential-a neon light connected between them and ground would be a super safe way just in case they became energized through a fault.  Should be safe enough as long as the whole contraption is GFCI protected.

I guess I assumed you would not always have a bonded neutral to work with-if you wire and demo a true delta.

I'm mostly interested in demonstrating the types of 3-phase configuration that technicians could find in an entrance panel. I've never seen a floating delta entrance panel in the field, but maybe I wasn't looking hard enough. I've seen tons of 4-wire WYE and 4-wire High-Leg Delta, and an occasional 3-wire Grounded-Leg Delta, but the beauty of this open transformer architecture on my "white board" is that it would be pretty simple to wire up anything strange into the demo. I've read about Open-Delta 3-phase and understand its limitations, but never encountered one. But there's a first time for everything, I suppose....
Title: Re: 3-phase power demonstration
Post by: Stephen Swaffer on December 31, 2018, 05:30:24 pm
I'm mostly interested in demonstrating the types of 3-phase configuration that technicians could find in an entrance panel. I've never seen a floating delta entrance panel in the field, but maybe I wasn't looking hard enough. I've seen tons of 4-wire WYE and 4-wire High-Leg Delta, and an occasional 3-wire Grounded-Leg Delta, but the beauty of this open transformer architecture on my "white board" is that it would be pretty simple to wire up anything strange into the demo. I've read about Open-Delta 3-phase and understand its limitations, but never encountered one. But there's a first time for everything, I suppose....

Hopefully they would never encounter it.  Just seems like every time I say "never"-and if I had a nickel for every time tech support or OEM techs told me "We've never seen that before"...
Title: Re: 3-phase power demonstration
Post by: Frank Koenig on December 31, 2018, 06:57:27 pm
I've read about Open-Delta 3-phase and understand its limitations, but never encountered one.

I was under the (maybe mistaken) impression that most of the high-leg delta you see is also open delta. I base this on the transformers I see on the poles in all the light industrial areas around here. There's always a big pot with 3 secondary wires coming out and a little pot next to it with 2. I assume the big pot is 240 V center tapped with the center tap grounded and providing the neutral, while the little pot is just 240 V. Each primary is connected across one of two different phases and the POCO rotates which two as they go down the street to balance things out. Is this right or just an elaborate product of my imagination? Thanks.

The white board looks like a great idea, BTW.

Happy New Year to you all.

--Frank
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on December 31, 2018, 07:50:31 pm
I was under the (maybe mistaken) impression that most of the high-leg delta you see is also open delta. I base this on the transformers I see on the poles in all the light industrial areas around here. There's always a big pot with 3 secondary wires coming out and a little pot next to it with 2. I assume the big pot is 240 V center tapped with the center tap grounded and providing the neutral, while the little pot is just 240 V. Each primary is connected across one of two different phases and the POCO rotates which two as they go down the street to balance things out. Is this right or just an elaborate product of my imagination? Thanks.

The white board looks like a great idea, BTW.

Happy New Year to you all.

--Frank

I can imagine how this could work with reduced capacity on the 120/240-volt split transformer, but I'm mostly looking at power inside of the building and ignoring the transformers on the outside. Guess I'll start a new hobby.

A little Googling found this reference:

Open delta high leg

I have seen multiple instances of High leg implemented with two transformers in open delta configuration, where the neutral is the center tap of one of the transformers. I am trying to describe this and do not understand the objection that has twice been made.

I just found a good diagram of this, as the last one on the page: http://www.bmillerengineering.com/elecsys.htm and also Figure 10-18 in this book http://books.google.com/books?id=8cT8D9_WP7MC&pg=PA251&lpg=PA251#v=onepage&q&f=false BillHart93 —Preceding undated comment added 20:41, 17 October 2010 (UTC).

    The proposed edit said something like "one of the three transformers may be omitted" which is confusing to the reader since the object described in teh schematic diagram is called "a transformer". This three-phase transfomrer could be made out of a set of three individiual single-phase transformers, in which case an open delta would further allow only two transfomrers to be used. But was this in fact done? The point of high-leg delta was to provide for a small 120 V load in an otherwise 3 phase 240 volt distribution network, which would have been primarily 3 phase loads, warranting a 3-transformer bank (or a three-phase transformer). The citation in the proposed reference warnsa bout high-leg connections and shows an open-delta connection, but doesn't show an open-delta high-leg. --Wtshymanski (talk) 21:52, 17 October 2010 (UTC)

Diagrams in both links show open delta high leg with two transformers. As pointed out the first link needs to be scrolled to the bottom of its page. The second one points out Figure 10-18. Maybe you didn't look at all the figures?

The purpose of using high leg may sometimes be to provide for a small 3-phase load along with substantial single-phase loads, for which open delta works well. When the 3-phase load is large, all three are needed. I have seen more instances of open delta high-leg than with the full 3 transformers or 3-winding transformer.
Title: Re: 3-phase power demonstration
Post by: Stephen Swaffer on December 31, 2018, 10:31:36 pm
Then you have really fun installs like the one in this area.  Open delta high leg with 2 42 space  panels side by side.  One wired as you would expect.  The other wired to allow every' space to be used for a single phase load.  Inspectors?  In Iowa?  In the early 70's??

And yes, I've had to tie bands in-as this is a former church whose auditorium was used for occasional CCM concerts.  At least they called an electrician familiar with the building-I eventually installed a 14-50 receptacle for them.
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on January 01, 2019, 08:37:57 am
Hopefully they would never encounter it.  Just seems like every time I say "never"-and if I had a nickel for every time tech support or OEM techs told me "We've never seen that before"...

True, that....
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on January 02, 2019, 08:08:33 am
Thought you would like to see how I'm generating 3-phase/120-degree test files while waiting for my 3-phase signal generator from China. I have an Allen & Heath ICE-16 interface which will play back up to 16 channels of wave files. I only need 3 channels for this generator so I went into Audacity and generated a mono 30 minute sine wave at 60 Hz. I copied and pasted it onto two more tracks, then slipped tracks 2 and 3 by 5.55 ms and 10.11 ms to create tracks that are phase shifted 120 and 240 degrees at 60 Hz. I added dead air at the beginning of the slipped tracks, then soloed each track and output them as separate mono 16-bit/44.1 files.

Now, don't go nuts on me about the phase thing because I realize that this is a time delay simulating a phase shift at a particular frequency, in this case 60 Hz. I would have to come up with different delay times at 50 Hz or whatever.  ;D 

I loaded these mono files on a USB thumbdrive in the appropriate folders, and the ICE-16 plays them from outputs 1, 2 and 3 in the proper 0/120/240 degree relationships. This works perfectly and is the easiest backup signal generator I could come up with until my real signal generator arrives. At least I can experiment with everything else and get my white board ready for action.

Yes, I'll post a few videos of this demonstration in operation showing measurements for the various flavors of 3-phase power. Thanks for all your suggestions so far (except for the 3-phase potato generator). You guys really are my brain trust.   
Title: Re: 3-phase power demonstration
Post by: Jonathan Johnson on January 03, 2019, 01:54:01 am
So here's what I'm thinking about doing to demonstrate wiring of various 3-phase configurations. I was going to mount this on a piece of plywood, but my wife gave me an old white-board yesterday, so I started laying out how to mount the transformers on it. Then I drew out where I could mount 5-way binding posts for various connections and test points. After I did that with dry-erase markers it hit me. Why don't I just mount the transformers and 5-way binding posts on the whiteboard and put a hinge on the bottom so it can lay flat for transport or an overhead video camera, and it can flip up at an angle for direct viewing and testing by the class. I can literally sketch the various diagrams for standard Delta, Grounded-Leg Delta, High-Leg Delta, 3-leg WYI, 2-leg WYI and whatever else comes to mind (open leg Delta, perhaps?) right on the white-board, then hook it up using colored banana plugs. I can get 5-way binding posts in Black, Red, Blue, Green and Yellow (no white that I can find, but maybe yellow is OK), and get banana plug jumpers in these colors as well.

Are you planning to fly with this? Let me know when. I want to see what happens at the TSA checkpoint. I'll bring popcorn.  ;D
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on January 03, 2019, 07:11:57 am
Are you planning to fly with this? Let me know when. I want to see what happens at the TSA checkpoint. I'll bring popcorn.  ;D

Well, this will go in checked luggage along with printed copies of my Powerpoint presentation, but hopefully it will pass muster.  ;D

Once I was flying back from a microphone manufacturer with a pair of side-address mics for review packed in my carry-on luggage. This was back in the day when you could watch the X-ray screen as your luggage went through. When the security guy stopped the belt and called for help I looked at the screen, and I've got to admit that side-address condenser mics look a lot like pipe bombs. More security showed up and I had to show them the loaner receipt for the microphones. Everyone calmed down a bit, but they still took my carry-on bag apart (carefully) to confirm they were mics and not bombs.
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on January 04, 2019, 07:51:35 am
I just received notification from the USPS that the 3-phase signal generator has arrived at my local post office, so it might be delivered today or Monday. Just in time to mount it on the front of the white board along with the transformers. All my colored 5-way binding posts and banana jumpers are here as well, so tomorrow could be a build/test day. Too much fun!

Now I just need a 4-channel scope to show phase relationships.

 
Title: Re: 3-phase power demonstration
Post by: Stephen Swaffer on January 04, 2019, 12:31:49 pm
You need this:

https://www.fluke.com/en-us/product/electrical-testing/power-quality-analyzers/three-phase-power-quality-meters/fluke-435-series-ii

Just bill it to the job.....
Title: Re: 3-phase power demonstration
Post by: Dave Garoutte on January 04, 2019, 12:44:53 pm
You need this:

https://www.fluke.com/en-us/product/electrical-testing/power-quality-analyzers/three-phase-power-quality-meters/fluke-435-series-ii

Just bill it to the job.....

Yikes!  That costs more than the ANNUAL power bill for my 3-phase machine shop!
Title: Re: 3-phase power demonstration
Post by: Jay Barracato on January 04, 2019, 01:59:06 pm
Yikes!  That costs more than the ANNUAL power bill for my 3-phase machine shop!
Ok I clicked on it, let the ads start rolling in.

Sent from my Moto Z (2) using Tapatalk

Title: Re: 3-phase power demonstration
Post by: Mike Sokol on January 04, 2019, 04:10:13 pm
Yikes!  That costs more than the ANNUAL power bill for my 3-phase machine shop!

WOW! Just north of $6,000. Very pretty, but a tad over budget.  ;D
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on January 05, 2019, 07:01:19 am
WOW! Just north of $6,000. Very pretty, but a tad over budget.  ;D

With any amount of luck looks like I'll have a Siglent SDS1104X-E to demo next week. At $500 it's a little more affordable than the Fluke. There's a lan port on the scope you can link to your browser so you can watch the display in real time on a computer screen, which I'll output to a video projector. This seems like a great teaching tool since my little 3-phase signal generator will let me change the phase angles in real time. 
Title: Re: 3-phase power demonstration
Post by: Stephen Swaffer on January 05, 2019, 09:17:48 am
But it does beg the questions...if the phase angles are off:

What are A/V techs gonna do about it?

What difference will it make to single phase audio gear?
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on January 05, 2019, 11:32:05 am
But it does beg the questions...if the phase angles are off:

What are A/V techs gonna do about it?

What difference will it make to single phase audio gear?

There's no way that the phase angles can be off in power made by a generator since it's tied to how the poles are wound. And even if the phase angles were somehow off, there's nothing you could do about it. Of course single-phase gear could care less about phase angles, but 3-phase motors certainly do. But since it will never happen in the field I won't teach it. However, this would be a great platform to demonstrate how phase rotation works as it relates to 3-phase motors, something I will demonstrate in the class.

The reason for building this system is to demonstrate how to measure various 3-phase configurations you might find and what the reasons might be for a strange voltage reading. Now with this system I could show what the original 90-degree 2-phase power looked like, but that's not for this technician class. But it could be interesting if I was teaching an engineering class on phasor theory, something I'm not really qualified to teach but really interesting stuff.
Title: Re: 3-phase power demonstration
Post by: Tim Hite on January 05, 2019, 02:08:30 pm
Notify not working so following along. . .
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on January 12, 2019, 05:24:50 pm
Here it is, up and running. I just need to clean up the wiring a bit, but it makes 3-phase WYE 120/208-volts and 3-phase High-Leg-Delta 120/208/240-volts. Good that I had my new 4-channel scope for troubleshooting since I had accidentally flipped the polarity (notice I didn't say inverted the phase) of one of the transformers which gave me some really strange voltage reading with a volt meter. Plus I've added a phase rotation meter to the demonstration. I get to try this out in front of a tech class on Tuesday, so it's working just in time.
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on January 17, 2019, 04:47:32 pm
After I cleaned up the wiring, I packed it up in a little Gator case and took it to my seminar on Tuesday. I did the high-leg delta demonstration for the class, and it worked perfectly making 120/240-volts on the "office taps", 240-volts phase to phase for motors, and 208 volts neutral to high leg. I'm going to repackage this prototype to make it a bit more flight worthy since everything loosened up on the plane. But the concept is sound, and the class asked a ton of questions about 3-phase connections. A few of the old-dogs in the class were able to talk about some of the local venues they work in that have high-leg delta panels, so now they understand why every third row of breakers is off-limits for audio power. And they also know why they can hook across all 3 phases for their chain motors (which are rated for 240-volts) and it will work just fine. Really fun class to teach.
Title: Re: 3-phase power demonstration
Post by: Dave Garoutte on January 17, 2019, 09:33:31 pm
Congrats!
It's fun when stuff works out.
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on January 18, 2019, 08:13:34 am
Congrats!
It's fun when stuff works out.


Yup... The Siglent SDS1104X-E scope is great since it not only has a Cat-5 network output you can view on a computer screen with a browser, you can also plug in a USB thumbdrive and take a screenshot anytime you like. This is a really great teaching tool for all kinds of demonstrations I have planned. Here's a screen shot of my 3-phase desktop demo. 
Title: Re: 3-phase power demonstration
Post by: brian maddox on January 18, 2019, 08:02:11 pm


Yup... The Siglent SDS1104X-E scope is great since it not only has a Cat-5 network output you can view on a computer screen with a browser, you can also plug in a USB thumbdrive and take a screenshot anytime you like. This is a really great teaching tool for all kinds of demonstrations I have planned. Here's a screen shot of my 3-phase desktop demo.

This is really great stuff.  Now i want to take one of your classes....
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on January 18, 2019, 08:22:59 pm
This is really great stuff.  Now i want to take one of your classes....

I'll see if I can get an invite to bring this class to AES. Will any of you be there?

147th Convention, New York, NY, USA
October 16-19, 2019
Title: Re: 3-phase power demonstration
Post by: Tim Hite on January 19, 2019, 11:06:51 pm
Would be awesome if you could do it over at the AES@NAMM seminars. Knowledge I would love to have.

I'll see if I can get an invite to bring this class to AES. Will any of you be there?

147th Convention, New York, NY, USA
October 16-19, 2019
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on January 21, 2019, 06:46:08 am
Would be awesome if you could do it over at the AES@NAMM seminars. Knowledge I would love to have.

There's not enough time to get on the schedule for AES/NAMM next week, but I'll work on 2020 AES/NAMM. I'll also see if I can hook up with some of the local AES chapters on the east coast. The 3-phase power demonstration along with using a NCVT for stray voltage detection would be a great 60-minute seminar. And adding how to use a clamp-ammeter to find ground-loop current hum would turn this into an informative 90-minute seminar. I'll contact the student AES chapter at Shenandoah University this week (my classes start tomorrow) to see what kind of interest there might be.
Title: Re: 3-phase power demonstration
Post by: Tim Hite on January 22, 2019, 02:49:30 am
ESTA now has a big presence at the winter NAMM show, as well. Maybe a better fit?

There's not enough time to get on the schedule for AES/NAMM next week, but I'll work on 2020 AES/NAMM. I'll also see if I can hook up with some of the local AES chapters on the east coast. The 3-phase power demonstration along with using a NCVT for stray voltage detection would be a great 60-minute seminar. And adding how to use a clamp-ammeter to find ground-loop current hum would turn this into an informative 90-minute seminar. I'll contact the student AES chapter at Shenandoah University this week (my classes start tomorrow) to see what kind of interest there might be.
Title: Re: 3-phase power demonstration
Post by: Mike Sokol on January 22, 2019, 07:48:38 am
ESTA now has a big presence at the winter NAMM show, as well. Maybe a better fit?

Ref: http://etcp.esta.org/

I contacted the ESTA a few years ago about presenting my Entertainment Electricity Seminars, but never heard back from them. Perhaps my new "Principals of 3-phase AC Power" seminar will break the ice and get them interested. Does anyone here have a contact with this group?