# 3phase motor



## TOO_SL:IM (May 13, 2010)

Howdy just quick Q I just installed a 30hp 3phase 240v submersible pump.The voltage is a Delta 240v with A 120v ,B (wild leg) 208v C 120v all to ground and 240v phase to phase.So I get my rotation right then start to set my overloads so the question is on A leg I get 68 amps on B leg 75amps on c leg 68 amps, and 7amps on the neutral. Why such a difference on the "B" phase,this makes it kind of hard to dial in the overloads when one phase is 7amps higher, any thoughts.


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## John Valdes (May 17, 2007)

You do not have a neutral on a 3 phase induction motor.
The high leg on a 3 phase motor is not a concern. Having a place to connect a neutral is.
Overloads are set to FLA.


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## ElectricArcher (Feb 25, 2010)

What did you connect a "neutral" wire to?


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## micromind (Aug 11, 2007)

A low of 68 amps, and a high of 75 amps is not unreasonable at all. 

It's only a 10% spread, pretty common for a submersible pump motor. 

As stated above, the neutral should not be connected to any part of a 3 phase motor. It's ok to use it for the control circuit, if the controls are 120 volts, but the only things that connect to the motor are the 3 phases and the ground. 

Rob


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## TOO_SL:IM (May 13, 2010)

Sorry my bad,let me explain.first your right this is a Delta 4wire system and the neutral landed only on the neutral lug of the combo service disconnect and starter.I dont know why I said I hooked up the neutral,I was just more focused on the difference in amps on the wild leg as compared to the others.Thanks for the answers.
Slim


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## micromind (Aug 11, 2007)

If the service is a 4 wire delta, and there are 120 volt loads, it's common for the high leg to have the highest current to a motor. 

The 120 loads will cause the voltage to be lower on the two 120 legs, and the imbalance will be reflected as higher current on the high leg. 

If you can transfer the 240 single phase loads that don't involve the neutral to the high leg and one of the other phases, it'll help.

Rob


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