ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Top Posters(30 Days)
twh 10
Admin 4
Recent Posts
Dryer, Range grounding from "Main" panel
by sparkync. 05/23/17 03:32 PM
Any UL 508 experts out there?
by sparkyinak. 05/21/17 08:57 PM
Heat pump conundrum
by sparkyinak. 05/21/17 08:49 PM
Interesting week
by HotLine1. 05/20/17 11:57 AM
Electrical Pricing Guide
by ElectricianBud. 05/18/17 12:17 PM
New in the Gallery:
SE cable question
Popular Topics(Views)
236,661 Are you busy
171,333 Re: Forum
164,393 Need opinion
Who's Online Now
0 registered members (), 82 guests, and 10 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate This Thread
#129836 - 09/19/05 01:22 AM Does this transformer exist  
PEdoubleNIZZLE  Offline
Member
Joined: Jun 2004
Posts: 176
McKeesport, PA, USA
I am trying to understand 3 phase a little bit better. I was wondering, is there such a thing as a transformer with a single phase input, and three phase output? Is it possible to make one? (I'm not talking about phase converters that use electronics or a motor/genset combo, i'm just talking transformer here)


Tools for Electricians:

#129837 - 09/19/05 07:40 AM Re: Does this transformer exist  
winnie  Offline
Member
Joined: Sep 2003
Posts: 649
boston, ma
If you are strict about the system being a pure transformer, then you cannot build a single to three phase transformer. This is because you need some sort of phase shift somewhere to produce the necessary phasing difference.

The simplest single to three phase converter is an induction motor. Note a motor/generator combo, but just a single motor. You supply single phase power between two of the terminals, and extract your third leg from the other terminal. The single phase supply stores energy in the rotation of the rotor, and you get that back (with pretty good phase shift) from the other terminal. This is probably the closest thing to meet the description of a single to three phase transformer.

Once you have at least two phases, you can use transformers to combine the two phases in appropriate proportions to get any other phase count. Apparently three phase to 12 or 18 phase transformer sets were (are???) sometimes used to feed power to rectifier banks to produce DC with very low ripple.

-Jon


#129838 - 09/21/05 12:58 PM Re: Does this transformer exist  
Tesla  Offline
Member
Joined: Jun 2004
Posts: 1,273
Sacramento, CA
Google rotary converters.

Static phase converters will be found, also.
http://www.homemetalshopclub.org/projects/phconv/phconv.html
http://home.att.net/~waterfront-woods/Articles/phaseconverter.htm

If you are willing to tinker, you can build your own rotary converter inexpensively.


Tesla

#129839 - 09/21/05 06:26 PM Re: Does this transformer exist  
Scott35  Offline

Broom Pusher and
Member
Joined: Oct 2000
Posts: 2,707
Anaheim, CA. USA
I like Winnie's descriptions using an Induction Motor.
May sound strange to some, but the Induction Motor is a Transformer with a "Spinning Secondary", and as pointed out by Winnie, the Aux. Winding of a 1Ø Induction Motor may be used to create a Polyphase output from a Single Phase input (by incorporating the Aux. Winding's lead with the 2 leads of the A.C. Power System).

As Mr. Spock would say: Fascinating!!!

Scott35


Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

#129840 - 09/22/05 12:27 PM Re: Does this transformer exist  
PEdoubleNIZZLE  Offline
Member
Joined: Jun 2004
Posts: 176
McKeesport, PA, USA
Thanks for the help. For some reason, I thought that if you could rotate a secondary out of phase, it would lead or lag, Instead, i hit me that it would decrease the amplitude...

Vout=Vsec*cosθ, where θ is the relative angle that you rotate the secondary.

The only way it would be possible without using moving parts would be to use 2 pieces of ferromagnetic material which are timed correctly behind and forward in the space-time continuum... or something like that


#129841 - 09/22/05 02:59 PM Re: Does this transformer exist  
winnie  Offline
Member
Joined: Sep 2003
Posts: 649
boston, ma
That technique works pretty well to change from N phases to M phases, where N is greater than 1.

You simply use a wound rotor motor, with the stator wound for N phases, and the rotor wound for M phases, and lock the rotor in position.

In one of my worksites, we used a wound rotor induction machine, which looks exactly like the transformer that you describe, with a three phase primary and a three phase secondary. The rotor was anchored to a gear box that let us rotate it, but would hold it in whatever position it was placed. By changing the rotor position we would change the phase of the voltage induced in the rotor coils. The rotor coils were connected 'buck/boost' to the feed lines, giving us a nice variable voltage three phase output.

-Jon


#129842 - 09/23/05 06:18 PM Re: Does this transformer exist  
Tesla  Offline
Member
Joined: Jun 2004
Posts: 1,273
Sacramento, CA
May sound strange to some, but the Induction Motor is a Transformer with a "Spinning Secondary", and as pointed out by Winnie, the Aux. Winding of a 1Ø Induction Motor may be used to create a Polyphase output from a Single Phase input (by incorporating the Aux. Winding's lead with the 2 leads of the A.C. Power System).
Scott35

To get the correct phase angle you’ll need a 3 phase induction motor as your ‘idler’ or rotary converter….

It does not need to be large. Typically a 2hp idler can support 7.5hp loads.

Visit my prior links.


Tesla


Member Spotlight
Bill Addiss
Bill Addiss
NY, USA
Posts: 3,878
Joined: October 2000
Show All Member Profiles 
Featured:

2017 NEC and Related
2017 NEC
Now Available!

Shout Box
Powered by UBB.threads™ PHP Forum Software 7.6.0
Page Time: 0.014s Queries: 14 (0.002s) Memory: 0.7861 MB (Peak: 0.9420 MB) Zlib enabled. Server Time: 2017-05-23 20:44:21 UTC