Question

what are the consequenses of increasing the supply frequency of a synchronous motor? in terms of Power, Heat and Torque.

Answer 1

We know that synchoronus motors are designed for a specific voltage per frequency ratio and is represented by V/Hz ,and this ratio is directly proportional to the magnetic flux developed in the windings. The torque developed in the shaft is of course proportional to the this flux which is rotating , so it is very important that the synchoronous motors works in the rated voltage per frequency ratio. So let us see what happens when supply frequency increases , it obviously decreases the voltage per frequency ratio and it result in decreasing the magnetic flux. As the magnetic flux reduces the torque also reduces proportionally,  and as it is directly proportional to the horse power of the motor so it is decreased and if the motor continues to be working in this situation the capability to run the load decreases and also results in heating of the motor.