# Phase Rotation



## pudge565 (Dec 8, 2007)

I'm going to give you guys a laugh while actually asking for an answer.

The first shift supervisor and I have a disagreement on phase rotation.

We have meat mix and viscera tankers with motor driven augers to unload them. They go to more than just our facility. Occasionally, we have to rewire a motor that runs in reverse. He is trying to get this fixed that we never have to rewire a motor, he says they have to be rewired because when the company that owns them cleans them the run the auger in reverse and forget to switch it back.

I told him that because these tankers go to other facilities we can't guarantee that the cleaners aren't putting it back the way it came to them. Phase rotation between facilities isn't necessarily the same. He swears that is is all across the country.

So I ask of you fine and intelligent gentlemen, who is right?


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## bkmichael65 (Mar 25, 2013)

There would be no need for phase rotation meters if he was right


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## McClary’s Electrical (Feb 21, 2009)

You are correct. If you are sharing with different facilities, you will always have this problem. I had a very smart, very respected electrician, try and tell me that the power company are getting better at it, and if you wire b, o, y, 1, 2, 3, it will be correct 99% of the time. I told him he had lost his mind.


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## pudge565 (Dec 8, 2007)

Best part is this guy is a "master electrician." I even pointed out about phase rotation meters and he still doesn't believe me.


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## J F Go (Mar 1, 2014)

pudge565 said:


> Best part is this guy is a "master electrician." I even pointed out about phase rotation meters and he still doesn't believe me.


Some people still don't believe we ever landed on the moon.So whats your point?:laughing: Just saying.If you read the new thread "grounding wire" you can get another stop me in my tracks look in your eyes.:whistling2:


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## bkmichael65 (Mar 25, 2013)

.......


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## theJcK (Aug 7, 2013)

phase rotation is one of the primary readings done in essential rollup to site.. point blank. one of the most overlooked things.. IMO.


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## AK_sparky (Aug 13, 2013)

Haha, I wish it was all the same. We put phase reversal monitor relay setups in some of our equipment so that it won't run if the input phases aren't correct. Other, less critical equipment we just have the installation/start-up instructions tell them to bump test.

Sounds like this guy has only ever worked in one place where the rotation is always the same.


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## DriveGuru (Jul 29, 2012)

Even if the phase rotation is correct(ABC), there is no EASA standard for AC motor direction relative to phasing. So it's a flip of the coin either way. It will depend on the motor manufacturer and or your motor repair facility. There is a standard for DC motor, but not AC. I don't know if maybe it because people change which side of the motor the connection box is on to suit their needs.


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## don_resqcapt19 (Jul 18, 2010)

I think that NEMA MG1 specifies that if you connect power with a rotation of ABC to the motor leads 1, 2, 3 the rotation will be counter clockwise when facing the motor opposite the drive end.


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## DriveGuru (Jul 29, 2012)

don_resqcapt19 said:


> I think that NEMA MG1 specifies that if you connect power with a rotation of ABC to the motor leads 1, 2, 3 the rotation will be counter clockwise when facing the motor opposite the drive end.



Often when a connection box is switch to the other side leads are not remarked. There may be a nema spec, Unfortunately most of the major motor rewind facilities in the country follow EASA specs. I've been round and round with them, and they tell me there is no EASA spec governing it, and they follow EASA repair guidelines. So in any circumstance, I believe it's always safest to verify the direction of your equipment


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## McClary’s Electrical (Feb 21, 2009)

Just install 3 position reversing disconnects on all equipment this is affecting.


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## McClary’s Electrical (Feb 21, 2009)

don_resqcapt19 said:


> I think that NEMA MG1 specifies that if you connect power with a rotation of ABC to the motor leads 1, 2, 3 the rotation will be counter clockwise when facing the motor opposite the drive end.


 nema mg 1 mandates rotation counter clockwise of single phase motors only. 24-1 does not apply to three phase, or polyphase motors.


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## OaklandElec (Jan 4, 2011)

Here it is standard for the POCO to hook up ABC so it is reverse rotation. By no means can you count on it though.


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## don_resqcapt19 (Jul 18, 2010)

DriveGuru said:


> Often when a connection box is switch to the other side leads are not remarked. ...


 I thought they just rotated the winding section of the motor 180° to swap the connection box side. The would not change the motor rotation when viewing the motor from opposite the drive end.

If they make the swap by switching the end bells and rotating the armature 180°, that would reverse the rotation when viewing from opposite the drive end.


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## don_resqcapt19 (Jul 18, 2010)

mcclary's electrical said:


> nema mg 1 mandates rotation counter clockwise of single phase motors only. 24-1 does not apply to three phase, or polyphase motors.


Thanks. I found an old copy of MG1 and the sections are somewhat confusing as they are talking about 3 phase phase sequence just before the rotation section, but even before that section they say this.


> 2.20.2 Induction Machines
> Terminal markings of polyphase induction machines are not related to the direction of rotation.


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## retiredsparktech (Mar 8, 2011)

don_resqcapt19 said:


> I think that NEMA MG1 specifies that if you connect power with a rotation of ABC to the motor leads 1, 2, 3 the rotation will be counter clockwise when facing the motor opposite the drive end.


When I worked as a motor tester at Louis Allis in Milwaukee, that was the standard, we followed. We referred to it as clockwise rotation, "think drill-motor". The leads had to be tagged on the three lead motors, which we built very few of.


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## Mshea (Jan 17, 2011)

I have had different phase rotation in the same facility at different panels. Main at abc and sub panel at cba.
I worked for a year in a rewind shop and while it was more than 30 years ago I am sure we never labled rotation. that said I do recall we had one job where we could not jog the motor so we used a rotation meter to be sure it was the correct way. Now if you have control over all the facilities this motor is to be used then ensure all the motor outlets are the same rotation then they will all work the same as soon as the motors are also wired for the same rotation.
Our utility would not check rotation except when changing the service drop on an existing installation. they do not normally define the incoming rotation unless there is alread 3 phase equipment that was sorking before.


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## DriveGuru (Jul 29, 2012)

don_resqcapt19 said:


> I thought they just rotated the winding section of the motor 180° to swap the connection box side. The would not change the motor rotation when viewing the motor from opposite the drive end.
> 
> If they make the swap by switching the end bells and rotating the armature 180°, that would reverse the rotation when viewing from opposite the drive end.



In an AC motor the stator winding is actually the armature, in a DC motor the rotating element is the armature. Once a motor winding is wound and installed in a core there is no way of removing the winding and core without destroying the winding, so if you need the box on the other side, you pull the rotor, reverse it, and switch the endbells.


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