Single switch open-circuit fault diagnosis in brushless DC motor drivers with buck converters

The power inverters which frequently go wrong are the weakest part in brushless DC (BLDC) motor drive systems. Thus, fault diagnosis of power inverters is the key point in the fault-tolerant control of BLDC motors. In this paper, the normal and faulty operating states of BLDC motor power inverters with buck DC-DC converter before the three phase full bridge were analyzed in detail. A straightforward method of single open-switch fault diagnosis in three phase full bridge inverters and buck DC-DC converters of the motor driver was proposed with only one current sensor. The measured DC-link currents and the six different operating states in 360 electrical degrees were used to detect the single switch open-circuit fault and to identify the faulty switch. Also, a protective circuit was designed to avoid the occurrence of the secondary fault. Both simulation and experimental results carried out confirm the feasibility and effectiveness of the proposed method for diagnosing single switch open-circuit fault in power inverters.