Abstract: This paper proposes an improved rotor fault detection algorithm. The
main objects are: First, ameliorate the reliability of the rotor fault
detection task especially under very low load in the presence of industrial
frequency inverter. Second, allow even relatively unskilled users to make an
automatic, fast and reliable decision on machine health with low requirements.
Basing on the concept of multiple signature processing, the proposed algorithm
uses Relative Harmonic Indexes (RHI) as a new fault indicator. The RHI are
computed starting from many harmonics selected carefully according to their
sensitivity to the occurrence of rotor bar faults, this represents its main
advantage compared to the classical fault indicators which use only one or two
fault signatures leading commonly to erroneous diagnosis especially under low
load. The proposed algorithm requires only the stator current signal. For each
data acquisition, the algorithm computes, normalises and classifies the RHI
then it displays the obtained results in a simple manner. Extensive
experimental tests, carried out on a 3 kW squirrel cage induction motor fed
from an industrial frequency inverter, confirm the effectiveness of the
proposed algorithm in detecting of rotor bar fault under different operation
conditions even with very low loads.
