On-line diagnostics in inverter fed induction machines using high frequency signal injection

Fault diagnostics for induction machines using an injected high frequency carrier signal is presented and analyzed in this paper. Both stator winding fault and broken rotor bar detection is covered. Measurement of the resulting high frequency negative sequence current is shown to be capable of detecting both types of faults at their incipient stage. Though sharing similar physical principles to techniques applied to line-connected machines, the use of a high frequency signal is shown to provide important advantages for inverter fed machines, such as providing the same performance and drastically reduced sensitivity to the working condition of the machine, i.e. torque and flux levels, and fundamental excitation frequency.