ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat Box
Recent Posts
Lock-down Thread
by Bill Addiss - 02/27/21 01:16 PM
Northern Tool Recalls Powerhorse Generators
by Admin - 02/25/21 09:49 PM
You will never guess
by gfretwell - 02/25/21 07:48 PM
New tool
by SMOKEYBOB - 02/15/21 04:59 PM
New in the Gallery:
Facebook follies, bad wiring
FPE in Germany pt.2
Who's Online Now
0 registered members (), 20 guests, and 18 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Page 1 of 2 1 2
3 phase motor powered by single phase #75116 02/14/07 07:31 PM
Joined: Jan 2005
Posts: 71
S
sid123456 Offline OP
Member
Has anyone ever come across a 3 phase motor powered by single phase? I came across this at a tire shop today. The motor is 3 phase on the name plate but it has a cord with just 3 wires in it. 2 to the motor and 1 grounded to the frame. Open up the pecker head and the taps don't match the high or low voltage diagrams. My boss said I was crazy. That you couldn't do that without a phase converter which there was not. But I've heard an old hillbilly tell me before it was possible.

Work Gear for Electricians and the Trades
Re: 3 phase motor powered by single phase #75117 02/14/07 08:14 PM
Joined: Dec 2000
Posts: 4,287
electure Offline
Member
Does it also have a large capacitor (or2) on it?

I've found 3Ø motors on single phase Euro machinery that manufactured their own 3rd Ø.

Re: 3 phase motor powered by single phase #75118 02/14/07 08:21 PM
Joined: Jan 2005
Posts: 5,316
renosteinke Offline
Cat Servant
Member
It is possible, with the use of the appropriate capacitors, etc., to "create" a third phase. It's won't be true three phase, but it will get things spinning the right way.

I'm not about to try to explain the 'how' or the 'why' .... but, since you mentioned that the tap hook-ups were unusual, it is possible that something like that was done.

The other thing you said that caught my attention was "auto shop." I have seen more screwed-up compressor arrangements in auto shops that in all other locations combined. I would almost say "if you saw it in an auto shop, there is no way what you saw was correct."

I suspect that, if you checked, that the motor is performing very poorly. That is, running hot, gobbling power, and not performing anywhere near its' capacity.

Re: 3 phase motor powered by single phase #75119 02/14/07 08:31 PM
Joined: Jan 2005
Posts: 71
S
sid123456 Offline OP
Member
They do have 2 capacitors..... Very interesting.

Re: 3 phase motor powered by single phase #75120 02/14/07 09:32 PM
Joined: Nov 2002
Posts: 456
C
classicsat Offline
Member
I got free 3Ø 3/4 HP motor one, and run it on 240V with capacitor from an A/C compressor. It is on my power washer.

Re: 3 phase motor powered by single phase #75121 02/15/07 06:44 AM
Joined: Mar 2005
Posts: 1,213
S
SteveFehr Offline
Member
Good explanation of the circuit on this site: http://www.gwm4-3phase.com/uands/static1.htm

[Linked Image from gwm4-3phase.com]

Re: 3 phase motor powered by single phase #75122 02/15/07 07:40 AM
Joined: Sep 2005
Posts: 153
W
Wolfgang Offline
Member
This way of wiring is quite known in Europe as "Steinmetz wiring". It is limiting the motor to about 70% of its nominal power on 3 phases. So it has to be oversized. In some applications it may overheat due to unregular wave form etc.

On the other hand there is a certain number of applications where smaller 3 phase motors can be wired in Steinmetz alternatively.

Last I saw was a fan in a big blower housing where all necessary data was directly given on the name plate.

Re: 3 phase motor powered by single phase #75123 02/15/07 11:58 AM
Joined: Jun 2006
Posts: 613
M
mikesh Offline
Member
I have seen the big rotophase converters and recently I had a look at a VFD that used a 240 volt single phase input with a variable frequency 3 phase output. It was on a milling machine and the VFD gave him even more speed control than through the gearbox alone.
It was under $1000 CDN for up to 5 horse power.

Re: 3 phase motor powered by single phase #75124 02/15/07 01:38 PM
Joined: Dec 2005
Posts: 860
R
RODALCO Offline
Member
There is an other thread regarding this topic too on ECN with schematics.

It works well. I do the same to convert single phase to three phase in my workshop and then start 3 Ø motors of the running main (3Ø running on 1Ø) motor.

Most motors under 3 HP start directly with no problems from the RST main terminals.


The product of rotation, excitation and flux produces electricty.
Re: 3 phase motor powered by single phase #75125 02/15/07 03:30 PM
Joined: Jan 2003
Posts: 4,391
I
iwire Offline
Moderator
Check out this thread.

I found it interesting.

Hillbilly Sawmill


Bob Badger
Construction & Maintenance Electrician
Massachusetts
Page 1 of 2 1 2

Featured:

2020 National Electrical Code
2020 National Electrical
Code (NEC)

* * * * * * *

2020 Master Electrician Exam Preparation Combos
2020 NEC Electrician
Exam Prep Combos:
Master / Journeyman

 

Member Spotlight
Scott35
Scott35
Anaheim, CA. USA
Posts: 2,721
Joined: October 2000
Show All Member Profiles 
Top Posters(30 Days)
Popular Topics(Views)
275,440 Are you busy
209,338 Re: Forum
196,620 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.7.3