Patent ID: 6738718
Filing Date: 2004-05-18
Classification: G01R,H02P

Abstract:
An apparatus for measuring torque and flux current in an AC synchronous drive motor having a shaft coupled to an a-phase, a b-phase and a c-phase, comprising:(a) an absolute shaft position indicator that is magnetically coupled to the shaft and that generates a position signal indicative of a position of the shaft; (b) a current sensing circuit that generates a current signal indicative of instantaneous direct link current of the motor; (c) a sample and hold amplifier that includes a trigger input and that samples the current signal, having a current signal value, when the trigger input is asserted; and (d) a processor, responsive to the position signal, that asserts the trigger input when the following events occur: i. the position signal indicates that each of the a-phase rotor, a b-phase rotor and a c-phase rotor is at a position where the internal back electromotive force for any phase is at either a maximum or a minimum; ii. when a voltage vector corresponding to a maximum or a minimum for a corresponding phase is applied to the motor; and iii. when the dc link current pulse-width meets a minimum requirement, the processor also responsive to the current signal so as to calculate torque generated by the motor and flux current in the motor based on the current signal value at a time when the trigger input is asserted.