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#1 ram14375

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Posted 05 March 2006 - 03:41 AM

Dear sirs,
we have two identical slip ring induction motor of 11kv,2100 kw,137 amps ,rotor voltage 1160v ,1105 amps started by seperate LRS used for driving ball mill. The average operating kw of the motor is around 1900kw.The required ball mill starting torque is around 150% of rated trq.

we have another slip ring induction motor of 1900kw ,134 amps,rotor voltage 1425v,805 amps rotor current .
can we use the above motor to substitute one of the running motors . If so what will be the impact on electrical and mechanical side. can anyone help
thanks
ram

#2 jOmega

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Posted 19 April 2006 - 08:47 PM

Hello Ram,

I suspect that you did not receive any replies to your posting because you did not provide sufficient technical information and detail of the motors and the application and how the motors are configured and how they are mechanically coupled to the driven load.

That being said, I offer the below.

If your 'another slip-ring induction motor" was rated identical to the primary motors used on the Ball Mill ... there wouldn't be any problem and you would not have asked your question.

However, 1900 kW motor is NOT equal to 2100 kW motor.
It provides less torque/ampere of current.

The rotor voltage and current are higher in the 1900 kW motor and will have the effect of overloading the controller connected to the motor rotor (it doesn't matter if the controller is resistor banks, or a solid state/magnetic type controller, it will be overloaded.)

Starting is another consideration ...
You said that starting is 150% of rated torque --- but that is 150% of rated torque of a 2100 kW motor.... which is quite a bit more starting torque than 150% of a 1900 kW motor.

Without more information, I would not advise you to consider using the 1900 kW motor in place of the 2100 kW motor. You might not be able to get it started because it cannot develop enough torque.... and you could destroy the motor by asking it to deliver more torque than it is capable of doing in the starting mode.

Kind regards,

jΩ




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