Fault tolerant control method of seven-phase BLDC motor in asymmetric fault condition due to open phase

Open-switch faults of seven-phase BLDC (brushless DC) motor drive system cause torque ripple. This torque ripple makes unwanted noise and vibrations in the drive system. In particular, open-switch fault case of one-switch or two-switches in the same phase among fourteen switches of PWM inverter is analyzed. This paper proposes two fault tolerant control (FTC) methods for seven-phase BLDC motor in asymmetric fault condition due to open switch fault. One can reduce the torque ripple to similar level under the healthy condition. The other can partially compensate the output torque. The proposed method changes the conductive angle of the healthy phase current. The usefulness of this paper is verified through simulation results.