Evaluation of the Virtual Third Harmonic Back-EMF in Identifying Misaligned Hall-effect Position Sensors in Brushless DC Motor Drives

In this study, a robust fault diagnostic technique, based on the virtual third harmonic Back-EMF, is proposed to identify the Hall-effect position sensor misalignment in Brushless DC (BLDC) motor drives. The proposed technique can also be exploited in sensorless BLDC drives to highlight the commutation errors and, consequently, the unbalanced operation of a BLDC motor drive, either sensor-based or not, can be detected. Therefore, potential signals, which incorporate the virtual third harmonic Back-EMF, are investigated in the frequency domain for a reliable diagnosis of the defective system. Through the comparison of the pros and cons of each signal, the voltage difference between the neutral point of a resistor network and the half of the DC-link is proposed for the development of the diagnostic technique. Thus, this signal is evaluated in identifying both the unbalanced system operation and the severity of the defect in a wide speed and load range.