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Maximum Frequency


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I have the following application:


Motor: 300Hp/2000V/40A/60Hz


VSD: 520KVA@480V


Power Supply: 50Hz/380V


What is the maximum frequency I can run the motor ?


Maybe 100?

Only 2 questions:

Where 2000 V will be taken from?

What the 480V VSD will be doing in the application ?

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Hello Cesar


The maximum frequency that you can run the motor is dependent on two major considerations.


1. The maximum speed that the bearings can operate at. Check with the motor manufacturer or bearing supplier.


2. The speed torque curve of the driven load. As you change the frequency, you change the power capacity of the motor.

At frequencies below the rated frequency of the motor, the voltage applied to the motor must be reduced proportional to the frequency reduction. This results in constant torque below rated frequency and ad power is torque times speed, the power capacity of the motor reduces with reducing frequency.

Above rated frequency, it is normal for the voltage to be limited to rated voltage by the magnitude of the supply voltage. This reduces the flux in the iron as the frequency is increased and reduces the torque output of the motor. bove rated frequency, the motor can deliver rated power.

As the speed of the load is increased, the torque required to drive the load typically increases.

The maximum frequency may be limited by the torque requirement of the load and the torque capacity of the motor.


Best regards,


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