Patent ID: 9634599
Date: 2017-04-25
CPC Classifications: H02P

Claim:
1. A method for operating a piece of equipment driven by rotary power comprising: coupling a permanent magnet AC motor to a shaft of the piece of equipment, the shaft adapted to be rotated directly by the permanent magnet AC motor, the permanent magnet AC motor including a stator and a rotor, the rotor having a permanent magnet positioned thereon; supplying alternating current to the stator; rotating the shaft; injecting a direct current in the opposite direction of a magnetic flux created by the permanent magnet and weakening the magnetic field of the permanent magnet; and increasing the speed of the permanent magnet AC motor to a maximum speed based on a speed ratio of the permanent magnet AC motor, the speed ratio defined as the ratio between the maximum speed and a rated speed, the rated speed corresponding to a rated voltage of the permanent magnet AC motor.