Can someone much smarter than I give me insight on this. Is it possible to vary only the output voltage of a 300KW generator to control a 150HP submersible pump with high initial torque requirements. They are using a soft start currently and someone questioned why it could not be done by varying the output voltage of the generator only. Any expert opinion on this would be appreciated.
Thanks

The speed of the motor is governed more by supply frequency than by voltage. However, because a motor represents an inductive load, and the impedance of an inductor reduces when the frequency is reduced, the voltage must be reduced also to prevent the reduction in impedance from allowing excessive currents.