Position sensorless startup for doubly salient electro-magnetic motor with only one test pulse

The self-inductance of doubly salient electro-magnetic motor (DSEM) varies with rotor position, so it's becoming an effective approach to estimate rotor position in DSEM sensorless drive system. Based on the feature that there must be a change in the magnitude relation of two phase self-inductances when the rotor goes from one sector to the other, this study proposes a novel rotor position estimation method for DSEM sensorless startup, it needs only one test pulse injection. The proposed method starts with injecting a test voltage pulse in all three-phase windings by turning on three proper transistors a certain time synchronously. Then at the end of the test pulse, the response currents of the two parallel-connected phases are sampled and compared for judging whether the rotor has reached the commutation instant. Moreover, the rotor position estimation error and output torque of the pulse-injection-based methods are theoretically analysed. Compared with the conventional rotor position estimating method which requires multiple test pulses, the proposed strategy has merits of less test time consuming, higher-accurate commutation, greater output torque and superior startup performance. Finally, the experiments on a 12/8-pole DSEM confirm the correctness and flexibility of the proposed method.