Sensorless Control of Induction Machines by Using PWM Harmonics for Rotor Bar Slotting Detection

The paper presents the use of the inherent high frequency PWM harmonics for sensorless control of AC machines. The amplitude and position of the PWM voltage harmonics cannot be controlled and depends on the fundamental machine operation. The paper examines the feasibility of sensorless control based on the extracted rotor bar slot position information in the case of a cage induction machine. The position signal demodulation and compensation schemes used are discussed. Experimental results of sensorless torque, speed and position control at loaded conditions including zero excitation and zero speed are given for an off-the-shelf induction machine.