Sensorless startup strategy for a 315-kW high-speed brushless DC motor with small inductance and nonideal back EMF

This paper presents a novel sensorless startup strategy for a 315-kW high-speed magnetic suspension brushless dc (BLDC) motor with small inductance and nonideal back electromotive force (EMF). Two key strategies on the sensorless startup strategy of the BLDC motor are presented: First, small current startup strategy for the high-speed BLDC motor with small inductance; and second, self-adaption control strategy to compensate the commutation error for the BLDC motor with nonideal back EMF in the startup stage. A hybrid pulsewidth modulation strategy based on the load torque is proposed to limit the startup current. An optimal motor startup curve based on the system parameters is presented, and a self-adaption control strategy is proposed to solve the synchronous switching problem. The effectiveness and feasibility of the proposed method is verified by a series of experiments on the 315 kW, 20 000 r/min magnetic suspension blower platform.