Experimental evaluation of low voltage off-line testing for induction motor rotor fault diagnostics

The off-line 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 (RIC). 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. Results of the low voltage test reveal that it cannot provide reliable diagnosis due to the low excitation flux level especially for motors with closed rotor slot design. The single phase rotation test and on-line current spectrum analysis are also performed under identical fault conditions to show that the fault conditions can be detected with standard tests.