3 phase motor conductor tracing

[ammklq143]

I have a customer who bought a used 3 phase motor and the motor conductors aren’t labeled, nor connected to anything. Some seem to be somewhat paired up with others but nothing clearly obvious or for certain.

It’s a 12 wire motor and the high voltage is like the high voltage delta diagram in the bottom left corner of the link below.

https://control.com/uploads/articles/Poster_3Phase_Motor_Wiring.png

Is there any way to determine which wires are which on this motor if they aren’t labeled? I’m not familiar with motor internal wiring, so I have no idea if this is possible or if he has to take it to a motor repair place and have them take it apart and label the conductors.

Thank you for any help.

 

[Jraef]

All of the leads are the ends of coils, so if they are all separated, you can wring them out with a meter to determine which pair of leads go to each coil. But on a 12 lead motor if they are not numbered or identified in any way, it's really difficult to determine which coils go with which coils to get the proper patterns. A motor shop can partially disassemble the stator to discover that, but I don't recommend you doing that in the field if you do not have a TON of experience with it.

But are all of the leads currently still connected as you say for the Hi voltage pattern? If so, then what's the problem?

 

[ammklq143]

All of the leads are the ends of coils, so if they are all separated, you can wring them out with a meter to determine which pair of leads go to each coil. But on a 12 lead motor if they are not numbered or identified in any way, it's really difficult to determine which coils go with which coils to get the proper patterns. A motor shop can partially disassemble the stator to discover that, but I don't recommend you doing that in the field if you do not have a TON of experience with it.

But are all of the leads currently still connected as you say for the Hi voltage pattern? If so, then what's the problem?

Thanks for the information. No, the leads aren’t connected to anything. There are a few that are bent and look like they were probably tied together, but not 100% sure. I’ll probably have him take it somewhere and have them figure it out.

Thanks again for the info.

 

[TwoBlocked]

It can be done. I have a copy of Preventive Maintenance of Electrical Equipment by Charles I. Hubert. I'll see if can find the section and get the info to you.

 

[TwoBlocked]

I remember one time some leads got mixed up on a motor and we passed a reduced current through a pair of coils by using the heating element of a heat gun, measured the voltage divisions, switched one of the coils and did it again. Can't quite remember the details, but it showed whether the coils were bucking up or bucking down, like with transformers. We did finally get the info from the manufacturer, and our investigation proved correct.

 

[TwoBlocked]

Guess I was thinking of another book. Found this on the enet, and seems similar to what I remember. Might be best to use an analog meter to se the inductive kick.

 

[Birken Vogt]

I was going to also look for that article but you found it already.

Be advised that if the coils are not wired correctly in the end that the magic smoke will come out.

 

[Deltaforce]

Be advised that if the coils are not wired correctly in the end that the magic smoke will come out.

Checking current equality in each pair three sets motor terminals with a battery and ammeter avoid it?

 

[Joethemechanic]

You have to break it down in steps. First find the pairs of wires coming off of each coil. Then you get a low voltage limited current voltage supply (Like a doorbell transformer) and connect it to a coil, and measure your output on all the remaining coils with a low impedance meter like a Simpson 260. The one with the highest voltage will be the corresponding coil that is wound in the same slots. Now you will have 3 pairs of two coils each. Then comes finding out which ends of the coils to use by connecting them in series and seeing if they are bucking.

This gets kind of long and there are some more steps. Lots of times it is just easier to disassemble the motor and see what goes where and replace the bearings while you're in there, megger the armature, look for banged up and shorted laminations, etc.

I'm trying to remember the whole electrical test procedure to id each wire, but I'm an old man, it's midnight, and I haven't had to do it in like 20 years. I don't want to tell you wrong

 

[MTW]

Here is the procedure for a 9 lead, the methods should be similar for a 12 lead, never done it myself.

You might find similar instructions for the 12 lead, at The frequently asked questions page at US motors given in the attached PDF.

FAQ

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