Experimental research on rotor fault diagnosis using external coil voltage analysis and shaft voltage signal analysis

Induction motors are nowadays used more frequently than any other electric motor in various kinds of electric drives. Incipient fault diagnosis is very important because if the fault is undetected, small motor failure can lead to serious motor failure. Although several sophisticated fault detection methods can be found in literature and practice, the focus of this paper are two methods that could be used ldquoon-linerdquo in real-life situations, and can be performed in a short time. The experiments have been performed by analyzing the voltage in an external search coil, and the shaft voltage. In the case of the search coil voltage analysis, the tests were performed for six different search coil positions. The search coil voltage spectral analysis has also been performed. All tests were performed on 22 kW, 380 V, 1470 r/min induction motor, for the case of a healthy rotor and for the case of a rotor with different deliberately damaged rotor.