Slot permeance effects on rotor slot harmonics in induction machines

Induction machines form the backbone of a substantial portion of the adjustable speed drives´ applications. Among the current estimation techniques available for speed-sensorless induction motor drives, speed measurement based on rotor slot harmonic (RSH) detection in machine line current happens to be a prominent one. The paper attempts to investigate the effect of slot permeance on the production of RSH. Simulation studies on a small motor but with a popular stator, rotor slot and pole combination suggest that their effect is less significant compared to rotor space harmonics effect. The cause of the less significant slot harmonic is shown to be the reverse rotating field caused by voltage unbalances and constructional imperfections and is thus absent in an ideal machine running from a balanced supply.