Advantages of PM-machines compared to induction machines in terms of efficiency and sensorless control in traction applications

The energy consumption of a permanent magnet synchronous machine (PMSM) is compared with the model of an induction machine (IM). Both machines are wheel-hub traction drives and developed for electric tramways. An overview contrasts the ability of sensorless control for the two machine types at different machine speed. The Indirect Flux detection by Online Reactance Measurement (INFORM) method at standstill and low speed and a back-EMF model at high speed provide sensorless control of the PMSM over the whole speed range. The quality characteristic of the two approaches (depending on speed and load), the implemented control structure and the influence of the INFORM test sequences on produced torque are discussed.