Detection technique for stator inter-turn faults in BLDC motors based on third harmonic components of line currents

This study proposes a technique for detecting stator inter-turn faults in brushless dc motors using the third harmonic components of line currents. The faults are attributed to insulation degradation between adjacent coils in a phase and, they cause distortions in the magnetic fields, which affect the harmonic components in line currents. To analyze the harmonic components under the asymmetric magnetic fields in a faulty motor, a system matrix is developed. As a result, the third harmonic components in line currents are noticeably generated in comparison to other harmonics, and the fault can be detected by determining whether the third harmonics exist. The proposed technique is verified by experiment under different operating conditions.