An apparatus and method for providing signals indicative of the magnitude and angular position of the DC motor flux of an AC induction motor is disclosed. The AC induction motor provides controllable rotation and torque in accordance with a drive current of variable magnitude and frequency. A first signal...http://www.google.com/patents/US4280085?utm_source=gb-gplus-sharePatent US4280085 - Apparatus and method for providing a signal proportional to flux in an AC motor for control of motor drive current
