Experimental investigation of rotor currents distribution in three phase induction motors with symmetrical squirrel cage at standstill

This paper simply investigates experimentally multiple “rotor” bar current waveforms at standstill, on a dedicated inside-out induction motor prototype as a basis to analyze the asymmetry of bar currents. A phasor calculus scheme based on primary MMF space harmonics is developed to explain this asymmetry of bar currents at standstill for a symmetrical cage. The results of the paper should be a strong experimental foundation to investigate thoroughly the effects of rotor speed and loading and of broken bars on additional losses, torque pulsations, noise and vibrations in high performance induction machines.