Extra Freedom Degrees of Six-Phase Induction Motors Used to Diagnose Stator Inter-Turn Faults

Multi-phase electrical machines have recently drawn growing attention and usage, among which, 6-phase induction motors (6PIMs) have gained an important part. They are main candidates to be utilized in the oil and gas industries, hot rolling mill drives, pumps, ship propulsion, and traction. Condition monitoring and fault diagnosis are essential technologies, which enable incipient fault detection and removal in order to prevent serious damages to the machines and catastrophic interrupt of them. Among the incipient faults, the stator winding inter-turn fault is a rather frequent one. In recent decades, numerous studies have dealt with this fault in three-phase induction motors, however, a few reports are available concerning 6PIMs. This paper applies the winding function method to model and simulate the 6PIM with inter-turn fault in a stator phase winding. Then, using the extra degrees of freedom in 6PIM, an analytical method is used to define an efficient index for detecting the stator inter-turn faults. This index also identifies the faulty phase of the stator, shows good sensitivity to the fault severity and is almost insensitive to the load torque change. Various simulation studies and corresponding experimental test results confirm effectiveness of the proposed index.