A New Approach to Flux and Torque-Sensing in Induction Machines

A new method of air-gap flux sensing in induction machines is introduced which is based on sensing the voltage across individual motor coils. By subtracting the voltage across two properly located motor coils a signal is obtained which is independent of stator ir drop and nearly independent of motor leakage reactance drop. By combining the proposed flux sensing method with conventional current transducers, the electromagnetic torque is readily computed. The method has been implemented in the laboratory and good correlation has been obtained for both sinusoidal and inverter power supplies.