Fault Diagnosis and Tolerance in Converters of Brushless DC Motor Drives for Low-Speed Applications

Condition monitoring and fault detection have become essential due to the growing need for reliabilityin motor drive applications. In electronically commutated motors, switching elements form the core components of the motor drives. These switching devices are prone to open-circuit faults (OCF) and short-circuit faults (SCF), which can impact the stability of the target application. This article introduces a simple switch fault diagnosis technique for brushless direct current (BLDC) motor drives, employing stator current sensing and sector information. The proposed method detects switch faults by monitoring the deviations in the conducting and non-conducting intervals of stator currents beyond their anticipated durations under normal conditions. Upon fault detection, the faulty legs of the converter are isolated and dynamically replaced by a two-leg redundant inverter. This reconfiguration is achieved by using low-cost electromechanical relays (EMRs). The fault-tolerant configuration ensures the motor operates at its rated power, even after experiencing up to two switch faults in the converter. In addition to fault detection and tolerance, the presented work also examines the severity of SCF, which causes abnormal stator currents due to three-winding conduction in BLDC motors. The effectiveness of the proposed approach is validated through experimental results obtained from a 36 V, 400 W BLDC motor drive.