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Author Topic: 3-phase power demonstration  (Read 7185 times)

Jay Barracato

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Re: 3-phase power demonstration
« Reply #30 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.

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Mike Sokol

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Re: 3-phase power demonstration
« Reply #31 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....   
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Tim McCulloch

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Re: 3-phase power demonstration
« Reply #32 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

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Mike Sokol

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Re: 3-phase power demonstration
« Reply #33 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.   
« Last Edit: December 11, 2018, 06:44:03 pm by Mike Sokol »
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Mike Sokol

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Re: 3-phase power demonstration
« Reply #34 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

« Last Edit: December 11, 2018, 07:12:59 pm by Mike Sokol »
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Tim McCulloch

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Re: 3-phase power demonstration
« Reply #35 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.

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"Practicing an art, no matter how well or badly, is a way to make your soul grow, for heaven's sake. Sing in the shower. Dance to the radio. Tell stories. Write a poem to a friend, even a lousy poem. Do it as well as you possible can. You will get an enormous reward. You will have created something."  - Kurt Vonnegut

Mike Sokol

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Re: 3-phase power demonstration
« Reply #36 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.
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Mike Sokol
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Tim McCulloch

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Re: 3-phase power demonstration
« Reply #37 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)
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"Practicing an art, no matter how well or badly, is a way to make your soul grow, for heaven's sake. Sing in the shower. Dance to the radio. Tell stories. Write a poem to a friend, even a lousy poem. Do it as well as you possible can. You will get an enormous reward. You will have created something."  - Kurt Vonnegut

Mike Sokol

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Re: 3-phase power demonstration
« Reply #38 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!
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Mike Sokol
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Mike Sokol

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Re: 3-phase power demonstration
« Reply #39 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. 
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Mike Sokol
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Re: 3-phase power demonstration
« Reply #39 on: December 12, 2018, 07:43:31 am »


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