Sensorless Speed Control of Single-Inverter Dual Motors based on Slotting Saliency Harmonic

Traditionally in single-inverter dual motor drives, two current sensors are attached to two inverter output phases. This is an economic option and often used by industry. Applying this configuration to saliency-based sensorless control is challenging, since both motor saliency waves may present opposite phase. In this case, the sum saliency signal, calculated by the current responses obtained by the two current sensors, would lead to zero and no rotor position would be available.In order to obtain two saliency signals, one for each motor, and thus avoiding the zero saliency sum, this paper investigates the use of three current sensors instead, where two are attached to the phases of the first motor and the remaining one to a phase of the second motor. With this current sensor configuration, voltage step excitation strategy is applied. In the proposed test bench, two similar induction motors are fed by a single inverter and mechanically coupled by a belt drive that allows opposite phase slotting synchronous signals. It will proven by experimental measurements that each motors’ sensorless position can be accurately calculated regardless of the phase shift between both slotting signals using the three current sensor.