Dear sir,

Iam using a electronic system called conveyor belt in which motor is connected with ac drive of 3hp, our indicator gives 4-20milli amp to drive and accordingly drive runs the motor , so tell me what role does frequency play.

Uh, let's see, you have a conveyor belt being driven by a 3HP motor controlled by an AC drive. The drives output is controlled by a 4-20 mA signal.

I'm not sure exactly what you're asking about frequency, but I'll say this: the drive varies the frequency to the motor based on the control circuit input, thereby varying the speed that the motor operates. The higher the frequency, the faster the motor runs, and vice versa.

This sounds suspiciously like a test question, and if this is true, I would strongly suggest that you seek some assistance, whether it be with classmates or possibly a tutor. If you're working on this level of motor control you should already have a solid understanding of AC and DC theory.

Whatever the case, I hope this helped:D