> "UPNDOWN" wrote in message
> news:1192247760.615168.186210@k35g2000prh.googlegroups.com...

>> The application of the motor is on a hydraulic lift.
>>
>> Originally the unit had a 15hp motor. Line voltage is 485v 3 phase.
>>
>> Someone at our company, decided to order a new pump unit, and ordered
>> a unit with a 30HP 3phase motor.
>> The motor runs fine when the lift is empty, or close to full load.
>> When it gets up near full load the motor leads get hot, the amperage
>> starts going off scale, the line voltage drops about 10 to 15 volts.
>> The motor bogs down until the overload trips.
>>
>> The warranty department/field engineering has told them to replace the
>> motor, pump, valve, none have which have made a difference. They
>> said the motor being larger wouldn't cause this. I guess they think
>> the bigger HP motor is not being asked to do more work than the old
>> 15hp motor, and should have no problems.
>>
>> The crew doing the work, asked me. My reaction was the motor is to
>> big, install a 15hp or 20hp motor. My reason being is the wire going
>> to equipment is to small, and is causing the voltage drops at higher
>> current.
>>
>> I'm asking for more opinions on this problem, and some insight on
>> what is happening to this 30Hp motor.
>>

> If you are running the pump on a circuit rated for fifteen HP then I'm
> sure that is your problem, like you suspected.