Experimental Evaluation of Low-Voltage Offline Testing for Induction Motor Rotor Fault Diagnostics

The offline single-phase rotor rotation test is frequently used in the field for assessing the integrity of the rotor cage without motor disassembly. However, the inconvenience of the large variable voltage supply requirement has triggered the advent of a portable low-voltage version of the test also known as the rotor influence check. This test has recently become common in the pulp and paper industry as it is convenient to use in an industrial environment. However, concerns on the reliability of the test have been raised due to frequent false test indications. The objective of this work is to provide an analysis and experimental evaluation of low-voltage rotor tests under controlled rotor fault conditions on 380-V and 6.6-kV motors. The results of the low-voltage test reveal that it cannot provide reliable diagnosis due to the low excitation flux level, particularly for motors with the closed rotor slot design. The single-phase rotation test and online current spectrum analysis are also performed under identical fault conditions to show that the fault conditions can be detected with standard tests.