ProSoundWeb Community

Please login or register.

Login with username, password and session length
Advanced search  

Pages: 1 [2] 3 4 ... 11   Go Down

Author Topic: 3-phase power demonstration  (Read 4194 times)

Mike Sokol

  • Moderator
  • Hero Member
  • *****
  • Offline Offline
  • Posts: 3319
  • Lead instructor for the No~Shock~Zone
    • No~Shock~Zone Electrical Safety
Re: 3-phase power demonstration
« Reply #10 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
« Last Edit: December 07, 2018, 11:53:17 am by Mike Sokol »
Logged
Mike Sokol
mike@noshockzone.org
www.NoShockZone.org

Frank Koenig

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 602
Re: 3-phase power demonstration
« Reply #11 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.
« Last Edit: December 07, 2018, 10:36:42 am by Frank Koenig »
Logged
Yes, it is a giant stereo system!

Nathan Riddle

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1498
  • Niceville, FL
    • Nailed Productions
Re: 3-phase power demonstration
« Reply #12 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]
« Last Edit: December 07, 2018, 10:26:35 am by Nathan Riddle »
Logged
I'm just a guy trying to do the next right thing.

This business is for people with too much energy for desk jobs and too much brain for labor jobs. - Scott Helmke

Jay Barracato

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1993
  • Solomons, MD
Re: 3-phase power demonstration
« Reply #13 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

Logged
Jay Barracato

Mike Sokol

  • Moderator
  • Hero Member
  • *****
  • Offline Offline
  • Posts: 3319
  • Lead instructor for the No~Shock~Zone
    • No~Shock~Zone Electrical Safety
Re: 3-phase power demonstration
« Reply #14 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.

« Last Edit: December 07, 2018, 11:51:20 am by Mike Sokol »
Logged
Mike Sokol
mike@noshockzone.org
www.NoShockZone.org

Tim McCulloch

  • SR Forums
  • Hero Member
  • *
  • Offline Offline
  • Posts: 19619
  • Wichita, Kansas USA
Re: 3-phase power demonstration
« Reply #15 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! 
Logged
"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

Tim McCulloch

  • SR Forums
  • Hero Member
  • *
  • Offline Offline
  • Posts: 19619
  • Wichita, Kansas USA
Re: 3-phase power demonstration
« Reply #16 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.
Logged
"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

Chris Hindle

  • SR Forums
  • Hero Member
  • *
  • Offline Offline
  • Posts: 1444
  • Montreal, Quebec, Canada, Earth, Sol System,......
Re: 3-phase power demonstration
« Reply #17 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.
Logged
Ya, Whatever. Just throw a '57 on it, and get off my stage.

Stephen Swaffer

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 2118
Re: 3-phase power demonstration
« Reply #18 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.
Logged
Steve Swaffer

Frank Koenig

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 602
Re: 3-phase power demonstration
« Reply #19 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
Logged
Yes, it is a giant stereo system!
Pages: 1 [2] 3 4 ... 11   Go Up
 


Page created in 0.066 seconds with 23 queries.