A Variable Duty Cycle Based Method for High Resistance Connection Fault Detection in BLDC Motor Drives

High-resistance connection (HRC) is a common issue in motor drive applications. These connections occur between the motor and inverter terminals, leading to voltage drops across the junction connectors and increased copper losses. HRC can create asymmetry in motor drive systems, degrading the motor's performance in terms of speed and torque. Therefore, reliable detection is crucial for implementing the mitigation techniques before the fault escalates and impacts the performance of the target application. This work proposes a new technique for detecting HRC faults in Brushless DC (BLDC) motor drives. In this technique, the DC link voltage across the motor terminals is varied for a fixed duration in an electrical cycle by adjusting the duty of the buck converter. This variation introduces a DC signal into the stator currents. By extracting the DC components from stator currents, it is possible to estimate the line resistances. Also, the severity of the fault is assessed using symmetrical component transforms. The proposed method is immune to variations in inductance and symmetrical variations in resistance. The above claims are supported by analytical expressions and experimental results obtained from a 36 V, 500 $W$ BLDC motor drive.