A Coil Short-Circuit Fault Diagnosis Method Based on Overvoltage of Electromagnetic Coil in Active Magnetic Bearing

A short-circuit fault in the electromagnetic coil of the electromagnetic converter unit, which serves as the active magnetic bearing (AMB), has the potential to irreversibly compromise the stability of the AMB unit. This article proposes a rapid and precise methodology for diagnosing short-circuit faults in electromagnetic coils of AMB systems based on overvoltage. This article elucidates the mechanism of overvoltage generation when driving the electromagnetic coil in a silicon carbide (SiC) half-bridge switching power amplifier. This article presents an analysis of the influence of the driving circuit on the electromagnetic coil overvoltage and the relationship between the overvoltage amplitude and the electromagnetic coil impedance parameters. A theoretical analysis was conducted to ascertain the relationship between the degree of short-circuit fault in the electromagnetic coil and the overvoltage reflection coefficient. Based on this relationship, a Smith circle diagram was constructed. The overvoltage amplitude can be accurately determined by detecting it, thus allowing the degree of short-circuit failure of the electromagnetic coil to be identified. The AMB system was tested, and experiments were conducted on the degree of short-circuit fault and the overvoltage reflection coefficient of the electromagnetic coil. The results demonstrate that the method is highly accurate in fault diagnosis.