Generators and Electric Motors
[Home] - [HELP] - [Forums] - [Groups] - [Classified Ads] - [Subscribe] - [Books] - [Sponsors] -

Go Back   SmokStak > SmokStak® Vintage Electrical Equipment > Generators & Electric Motors General Discussion
Forgot Password? Join Us!

Notices

Generators & Electric Motors General Discussion Antique Generators and Old Electric Motors: Questions and answers about restoring and showing old power generation systems.

Generators & Electric Motors General Discussion

Three Phase to Single Phase via Transformer


this thread has 17 replies and has been viewed 51699 times

Reply
 
Thread Tools Display Modes
  #1  
Old 08-31-2012, 06:08:28 PM
Gunny Gunny is offline
Subscriber
 
Join Date: Feb 2005
Location: North Carolina
Posts: 3,832
Thanks: 1,842
Thanked 1,711 Times in 1,071 Posts
Default Three Phase to Single Phase via Transformer

Where can one find a 3 phase to single phase transformer?

Can you draw out the connections for one?
Reply With Quote
Sponsored Links
  #2  
Old 08-31-2012, 06:32:15 PM
BTPost's Avatar
BTPost BTPost is offline
Moderator
 
Join Date: Jan 2005
Location: Excursion Inlet, Alaska USA 99850-0090
Posts: 4,840
Thanks: 556
Thanked 1,864 Times in 1,206 Posts
Talking Re: Just bought a 2006 Onan 7.5HDKAL-3E Need some help

Actually in theory one could make, or wind one, but in practice NO ONE does, so it is just Theory. There is NO Practical difference between a Three Phase Genend, and a Three Phase Transformer Secondary. If one had a Three Phase Delta, or Wye, wound Primary Triple Core Transformer, and then wound what would be a 12 Lead Secondary with 2 Coils, on each of the Three Cores, you would have exactly what you are looking for... A Three Phase to Single Phase Transformer with all the same connection diagrams that a 12 Lead Genend can produce. This would include a Parallel Delta, or Double Delta Configuration. The math works out the same, in either case. Just Say'en.....
__________________
Bruce in alaska

Last edited by BTPost; 09-01-2012 at 01:55:22 PM. Reason: I decided to make this into a Sticky, because it is a very Common Topic
Reply With Quote
  #3  
Old 09-05-2012, 10:22:35 AM
Jim Rankin Jim Rankin is offline
Registered-III
 
Join Date: Nov 2004
Location: Faunsdale, Alabama USA
Posts: 4,436
Thanks: 71
Thanked 1,185 Times in 967 Posts
Default Re: Three Phase to Single Phase via Transformer

And the upshot of this exercise is that the single phase connected secondary will always have a lower capacity than when it's connected 3 phase.

The best you can do is to balance the load seen by the primary as well as possible which is what all the single phase reconnections accomplish.
Reply With Quote
The Following User Says Thank You to Jim Rankin For This Post:
  #4  
Old 10-14-2012, 10:15:29 AM
Jim McIntyre's Avatar
Jim McIntyre Jim McIntyre is offline
Subscriber
 
Join Date: Nov 2004
Location: Mooresville, Indiana, USA
Posts: 4,531
Thanks: 876
Thanked 2,697 Times in 1,542 Posts
Default Re: Three Phase to Single Phase via Transformer

I'm wondering what the original post is really asking. Is it that he wants to connect a single phase, say 120V load to a 480V 3-phase supply? Or is it that he has a 3-phase generator and wants use a transformer to 'convert' it for use with a single phase load? Is he hoping for a transformer-based circuit that somehow skirts around the 2/3 capacity reduction? Or something else?
Reply With Quote
  #5  
Old 10-14-2012, 12:26:23 PM
EricWood's Avatar
EricWood EricWood is offline
Registered-III
 
Join Date: Oct 2005
Location: West Concord, Minnesota USA
Posts: 1,989
Thanks: 247
Thanked 1,530 Times in 811 Posts
Default Re: Three Phase to Single Phase via Transformer

Jim,

I would guess the question is related to something like this:

http://www.nuteckproducts.com/three-...ansformers.htm


People seem to want a way to pump their 3-phase genset into a transformer and get the single phase 240V "house power" out of it, so the full capacity of the generator can be utilized. Transformer would need to be sized so single phase KVA output equaled that of the generator's capacity. A cost-prohibitive venture in my opinion.


This kind of transformer is not going to be on anyone's shelf in a warehouse I suspect; custom-built to your requirements.

eric
Reply With Quote
  #6  
Old 10-15-2012, 12:16:25 PM
Jim McIntyre's Avatar
Jim McIntyre Jim McIntyre is offline
Subscriber
 
Join Date: Nov 2004
Location: Mooresville, Indiana, USA
Posts: 4,531
Thanks: 876
Thanked 2,697 Times in 1,542 Posts
Default Re: Three Phase to Single Phase via Transformer

OK, well I'm curious about the connections for that "3-phase to single phase" transformer, too...
Reply With Quote
  #7  
Old 10-15-2012, 04:04:58 PM
pegasuspinto pegasuspinto is offline
Registered-III
 
Join Date: Oct 2006
Location: Floyd, AR, USA
Posts: 2,966
Thanks: 339
Thanked 1,421 Times in 925 Posts
Default Re: Three Phase to Single Phase via Transformer

Final word-there is no 'simple' way to convert 3 phase to 1 phase without significant loss of KW capacity. It may be possible to custom tune something with large capacitors and load coils, but I suspect it would require the load to be in a very narrow window and could dramatically increase the generator load once the load fell out of specs, possibly enough to start letting the smoke out of everything. Other way would be to convert the 3 phase to DC and invert it back to the AC power you want, but that's certainly NOT simple, or cheap. The small inverter type portable generators (Honda and it's clones) work exactly that way. But price would get crazy once you were past 1-2kw.


Robert
Reply With Quote
  #8  
Old 10-15-2012, 11:09:28 PM
BTPost's Avatar
BTPost BTPost is offline
Moderator
 
Join Date: Jan 2005
Location: Excursion Inlet, Alaska USA 99850-0090
Posts: 4,840
Thanks: 556
Thanked 1,864 Times in 1,206 Posts
Talking Re: Three Phase to Single Phase via Transformer

Quote:
Originally Posted by pegasuspinto View Post
Final word-there is no 'simple' way to convert 3 phase to 1 phase without significant loss of KW capacity. It may be possible to custom tune something with large capacitors and load coils, but I suspect it would require the load to be in a very narrow window and could dramatically increase the generator load once the load fell out of specs, possibly enough to start letting the smoke out of everything. Other way would be to convert the 3 phase to DC and invert it back to the AC power you want, but that's certainly NOT simple, or cheap. The small inverter type portable generators (Honda and it's clones) work exactly that way. But price would get crazy once you were past 1-2kw. Robert
You miss- understand the issue here. If you can wind a Triple Core Primary Transformer with one winding per core, at the input voltage, and then wind twin seconday windings, on each of these cores. These secondary windings can be then configured the same as ANY Parallel Delta, or Double Delta, to make 120/240 Vac Single Phase output. The only real issue that needs to be designed into this transformer, is there needs to be enough iron designed into the cores, to carry the power from the three Phase side, to the single Phase Side. Much like an Extended Stack Genend.
__________________
Bruce in alaska
Reply With Quote
  #9  
Old 10-15-2012, 11:16:42 PM
Jim McIntyre's Avatar
Jim McIntyre Jim McIntyre is offline
Subscriber
 
Join Date: Nov 2004
Location: Mooresville, Indiana, USA
Posts: 4,531
Thanks: 876
Thanked 2,697 Times in 1,542 Posts
Default Re: Three Phase to Single Phase via Transformer

Quote:
Originally Posted by BTPost View Post
...The only real issue that needs to be designed into this transformer, is there needs to be enough iron designed into the cores, to carry the power from the three Phase side, to the single Phase Side.....
Yep, and then after you did all that, you'd still be left with the 2/3 derating that kicks in when a 3-phase source powers a single phase load...
Reply With Quote
  #10  
Old 07-10-2013, 09:48:08 AM
armandh armandh is offline
Sponsor
 
Join Date: Aug 2006
Location: Suburban St. Louis, Missouri
Posts: 3,098
Thanks: 294
Thanked 866 Times in 652 Posts
Default Re: Three Phase to Single Phase via Transformer

yes the extended stack gen sets could [with enough engine] produce 50% more 3 phase power.
thus the windings can produce 2/3 of that higher amount in double delta or zig zag single phase configuration.

the only way to get full power is to divide the load into 3 parts.
this has some VR challenges.
Reply With Quote
  #11  
Old 08-10-2017, 12:54:43 PM
BergmanJ
Guest
 
Posts: n/a
Default Re: Three Phase to Single Phase via Transformer

Folks,

There is a way to convert 3-phase to single phase; but, as BT indicated above, the efficiency is questionable, at best.

Here goes: Scott-Tee from 3-phase @ 120 degrees = 2-phase output @ 90 degrees; then series connect the two output windings with center connection isolated and insulated. Output from two "outside" leads at 240 volts (yes, need to "figure-out" the appropriate turns-ratios to obtain 240 here) to center-tapped auto-transformer (re-establishing "neutral" for 120/240 "split phase" from the center tap.

Again, not efficient; and, I have not figured-out the power-split ratios from all 3-phase windings; but, believe they are not evenly split. Don't know how this compares to derated single-phase use from 3-phase gen output, either. Guessing not a good!

This is more or less just an excercise for those interested in transformer phase conversion.

The direct opposite was used decades ago in 400 Hz aircraft power supplies to provide precision power to electro-mechanical gyroscopic navigation systems: Single phase to + and - 45 degree sources (provides 90 degree total differential outputs -- call one "zero" and the other "90") into two power amplifiers, then into scott-tee power transformers for three-phase power output to drive the gyro motors.

Regards, JLB
Reply With Quote
  #12  
Old 08-12-2017, 11:36:54 AM
armandh armandh is offline
Sponsor
 
Join Date: Aug 2006
Location: Suburban St. Louis, Missouri
Posts: 3,098
Thanks: 294
Thanked 866 Times in 652 Posts
Default Re: Three Phase to Single Phase via Transformer

getting the right voltage and phase relationship is NOT the same as getting the same power output.
the two [zig zag] legs in series use 2/3s the windings and power to produce half the output
Reply With Quote
The Following User Says Thank You to armandh For This Post:
  #13  
Old 08-12-2017, 11:56:05 AM
BTPost's Avatar
BTPost BTPost is offline
Moderator
 
Join Date: Jan 2005
Location: Excursion Inlet, Alaska USA 99850-0090
Posts: 4,840
Thanks: 556
Thanked 1,864 Times in 1,206 Posts
Talking Re: Three Phase to Single Phase via Transformer

If you choose the right Transformers with enough Copper & Iron, then you will have your correct AMP thru-put in the conversion....
__________________
Bruce in alaska
Reply With Quote
  #14  
Old 08-12-2017, 08:05:14 PM
armandh armandh is offline
Sponsor
 
Join Date: Aug 2006
Location: Suburban St. Louis, Missouri
Posts: 3,098
Thanks: 294
Thanked 866 Times in 652 Posts
Default Re: Three Phase to Single Phase via Transformer

generator too just like an extended stack

OK for a 240/480 delta or 380Y generator transformed to 120-0-120 single phase

but without enough Fe & Cu in the generator, problems still {IMHO}

there is always a weak link in the power chain. by design it should be the breakers or fuse.

no matter how it is configured.....

both the generator engine and the generator it self should handle more than the breaker,

or longevity will suffer.

Last edited by armandh; 08-13-2017 at 04:55:08 PM.
Reply With Quote
  #15  
Old 03-11-2018, 10:55:57 AM
TomBall TomBall is offline
Subscriber
 
Join Date: Dec 2012
Location: Perrysburg, New York
Posts: 395
Thanks: 8
Thanked 165 Times in 94 Posts
Default Re: Three Phase to Single Phase via Transformer

So in reading the responses, am I safe in concluding that if you had a three phase generator laying around and someone said you could easily wire it to run single phase power during outages, it is not that easy or efficient?
Reply With Quote
  #16  
Old 03-11-2018, 02:42:55 PM
Vanman Vanman is online now
Subscriber
 
Join Date: Aug 2011
Location: Mission Viejo, California
Posts: 6,011
Thanks: 9,899
Thanked 2,829 Times in 1,906 Posts
Default Re: Three Phase to Single Phase via Transformer

Many of them can be reconnected for 120/240 single phase, but all of them will be limited to 2/3 of their original three phase kva. That said there exist sets that are simply equipped with a larger generator, "extended stack" in Onan lingo, that have their three phase rating decreased such that they are rated the same kw for both single and three phase.
Reply With Quote
  #17  
Old 05-08-2018, 04:26:31 PM
armandh armandh is offline
Sponsor
 
Join Date: Aug 2006
Location: Suburban St. Louis, Missouri
Posts: 3,098
Thanks: 294
Thanked 866 Times in 652 Posts
Default Re: Three Phase to Single Phase via Transformer

Quote:
Originally Posted by Vanman View Post
Many of them can be reconnected for 120/240 single phase, but all of them will be limited to 2/3 of their original three phase kva. That said there exist sets that are simply equipped with a larger generator, "extended stack" in Onan lingo, that have their three phase rating decreased such that they are rated the same kw for both single and three phase.
"that have their three phase rating decreased"
[because the engine is smaller and matches the single phase output ability of the greater at 3 phase generator]
__________________
.
by using this free advise, you, your heirs, etc
absolve, save, and hold harmless the advisor.
CAVEAT EMPTOR
YMMV
Reply With Quote
  #18  
Old 05-24-2019, 07:35:01 AM
armandh armandh is offline
Sponsor
 
Join Date: Aug 2006
Location: Suburban St. Louis, Missouri
Posts: 3,098
Thanks: 294
Thanked 866 Times in 652 Posts
Default Re: Three Phase to Single Phase via Transformer

and for those pesky 208 Y 4 wire non re-connectable
https://www.smokstak.com/forum/attac...8&d=1558616360
a 120/120 XF with a current capacity equal to the generator leg
__________________
.
by using this free advise, you, your heirs, etc
absolve, save, and hold harmless the advisor.
CAVEAT EMPTOR
YMMV
Reply With Quote
Reply

Bookmarks


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

F o r u m Jump

Similar Threads Chosen at Random
Thread Thread Starter F o r u m Replies Last Post
Running Surplus 3-Phase Welders on Single-Phase Power dkamp Welding Shop 52 07-01-2019 08:00:02 AM
Another stupid question about converting from single phase 120v to single phase 240v! Patrick Onan Generators 7 11-30-2011 02:08:16 PM
Convert Onan 5.0CCK-5DR/8462V Three phase to Single phase RichardD Onan Generators 4 06-29-2011 07:48:56 AM
US Motor Div Generator Conversion To Single Phase 220V From Three Phase jimybud Generators & Electric Motors General Discussion 4 06-27-2010 08:19:50 PM
Transformer Question 3pahse to Single Phase richar22 Generators & Electric Motors General Discussion 21 12-02-2006 03:06:19 PM


Use "Ctrl" mouse wheel to change screen size.
All times are GMT -4. The time now is 03:46:33 PM.

Smokstak and Enginads site search!


All use is subject to our TERMS OF SERVICE
SMOKSTAK® is a Registered Trade Mark - A Community of Antique Engine Enthusiasts
Copyright © 2000 - 2019 by Harry Matthews P.O. Box 5612 - Sarasota, FL 34277