A.C. squirrel cage induction motor.

[michaelt]

Further to my question of June 15th, 2002.
The two 250 h.p. motors are Joy dual voltage star/delta 950/550 volts, the transformer feeding them is a 1mva 1100 volts Brush transfomer. We in Canada use U.K.transformers and switchgear because of our code. These motors are larger than we used before because the new generation of coal cutting machines are larger. The only response I need is yes or no. Thank you.

 

[electricpete]

You will have to clarify which yes or no question:

#1 - "does horsepower (output) increase"? My answer: maybe
#2 - "does current increase"? My answer: probably.

Not all questions can be answered yes or no but I invite other input since I'm sure the original poster is not satisfied with my answer.

 

[jbartos]

Suggestion: Regrettably, the motor nameplate data appear to be unavailable from the requestor.
Therefore, the correct answers may be:
1. Yes, maybe, and no.
2. HP=(1.73 x E x I x Eff x p.f.)/746
If E increases, HP increases.

 

[electricpete]

Change my answer to probably for both questions. Reasoning is in the previous message which is linked here:
thread237-25247

 

[cbarn24050]

Hi, the only thing I know for sure is that you will soon be able to have the motors rewound for 1100 volts.

 

[buzzp]

It will run for a while. You will reduce the life because you will have to turn up the OL setting (based on your previous post). If this OL setting is above the service factor amps then the motors life is reduced. So, yes the current draw will definately go up to do the same amount of work. The efficiency will decrease as well as the PF. The starting current will increase as well as available torque. The last two statements assume the load has not changed. However, I was told (not certain about this part) that the OL capacity of the motor will increase 21% with an increase in nameplate voltage by 10%. At the same time, the temperature will increase by 10%. Heat is what reduces the motors life. Bottom line-run the motor, expecting it too burn up sooner than otherwise. When it burns up have it rewound for your available voltage. Unless you can get the correct transformer. Good Luck.