On innovative methods of induction motor inter-turn and broken-bar fault diagnostics

A fault indicator, the so called swing angle, for broken-bar and inter-turn faults is investigated in this paper. This fault indicator is based on the rotating magnetic field pendulous oscillation concept in faulty squirrel cage induction motors. Using the "swing angle indicator", it is demonstrated here that an inter-turn fault can be detected even in the presence of machine manufacturing imperfections. Meanwhile, a broken-bar fault can be detected under both direct line and PWM excitations, even under the more difficult condition of partial load levels. These two conditions of partial load and motor manufacturing imperfections, which are considered as difficult situations for fault detection, are investigated through experimentally obtained test results for a set of 2-hp and 5-hp induction motors