Saliency-based Speed Sensorless Control of Single-Inverter Dual Induction Machines using Reduced Amount of Current Sensors

Parallel supply of dual-motors by single-inverter is a frequent practice, especially in traction applications. Model-based sensorless drives mostly rely on four current sensors, two of which attached to each motor. In the medium to high speed range, these model-based strategies can calculate the flux and torque share of each motor since the inverter output voltage is relatively linear. However, zero electrical speed operation turns out to be unstable as the system becomes unobservable. This area can be covered by injection strategies. This paper applies the voltage step excitation sensorless concept to dual-motor drives, which has not been researched in literature to the best of author's knowledge. Besides, a novel current sensor configuration is presented, using only three (instead of four) current sensors. Thereby, phase A and B currents of one motor (M1) will be measured, while the third sensor is attached to phase C of M2. As will be shown, new sensor arrangement allows for separation of individual machines inherent saliencies and thus delivers information of both machines rotor position, enabling a correct motor torque/flux share calculation by means of FOC equations. Experimental results prove the functionality of the new sensor configuration and voltage step excitation strategy applied to two parallel-connected induction motors.