Sensorless position cage induction motor drive using an asymmetric outer-section cage

This paper describes a new method of obtaining a rotor position signal from a cage induction machine operating without a mechanical sensor. The method is based on introducing a circumferential variation in the resistance of the outer section of either a double cage or deep bar cage rotor. The paper is aimed at showing the feasibility of the drive through simulation. The principle of operation is first described and a double cage machine model introduced which can represent the asymmetry. The model includes an indirect rotor flux orientated (IRFO) controller and signal processing for derivation of the position signal. Simulation results show the operation of the scheme as a position servo with low torque ripple.