# 3 phase motor



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

rumple said:


> What happens if a 3 phase 230/460 v motor is wired for 480 and the peckerhead leads are wired incorrectly? I'm not talking about t1 t2 and t3, I'm talking if the 7/4 9/6 and 8/5 are switched around somehow?


 

It could do lots of things, but most likely overheat the windings. Depending on what combination you screw up, it may not run at all.


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## Jlarson (Jun 28, 2009)

I can't think of _anything_ good that would come of incorrectly connecting the leads.


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## Wirenuting (Sep 12, 2010)

Jlarson said:


> I can't think of anything good that would come of incorrectly connecting the leads.


You can use the motor to make Jiffy Pop at lunch time.


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## Jlarson (Jun 28, 2009)

Wirenuting said:


> You can use the motor to make Jiffy Pop at lunch time.


 :laughing:, an angle I didn't consider.


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## BBQ (Nov 16, 2010)

Using this as a guide you could draw out wrong connections.


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## CJE (Oct 10, 2010)

I used to work for a company that did a lot of livestock feeding equipment. We had a customer who wanted to pull his own motor and take it to be repaired. When he got it back, he called and said they had messed it up, it ran backwards. I told him to change any two leads. He said he understood what I was saying. Never occurred to me at the time to specify the leads coming to the motor from the contactor. He called the next day, saying that that made it worse- didn't matter which two he changed, and he had tried it every way he could, it wouldn't run at all now, only make a loud buzzing noise, or try to turn really slowly. When I got there, I put everything back the way it should have been, and it ran fine. No way to know how much he might have shortened the life of the motor though.


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## micromind (Aug 11, 2007)

I've actually seen this a few times. 

The most memorable was a rock crusher that had two 300HP motors turning the same shaft. Both were 6 lead. Each one had its own across-the-lines starter, they were arranged sequentially. One motor would start, then about 10 seconds later the other (now turning) motor would be blasted across the lines. 

The correct connection is L1 = T1&T6; L2 = T2&T4; and L3 = T3&T5. 

The plant guys had to remove one of the motors, and when they re-installed it, they connected it wrong. L1 = T1&T6, L2 = T2&T5, and L3 = T3&T4. Connected this way, one of the 3 windings was shorted, the other two were in parallel; they should be 120º apart.

I was called in because the second motor (the one they wired wrong) would trip its O/Ls. 

I didn't ask to see it in action, at first I thought the motor was bad. But when I went to disconnect it, it just didn't look quite right. It took me a while to finally get it.

I connected it correctly, and it ran fine. As far as I know, it's still ok.

Rob


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