Circuit Analysis of Goerges Phenomenon in a Three-Phase Induction Machine

Unbalanced rotor impedance may lead to an induction motor operating at half of synchronous speed. This phenomenon was discovered by Hans Goerges in 1896. A 1950 paper by Garbarino and Gross gives an equivalent circuit for this unbalanced system. The circuit analysis results were validated by hardware experiments. The current paper is a tribute to Garbarino and Gross for the elegant analysis. We give a detailed explanation on how the equivalent circuit can be derived step by step using symmetric component theory along with an understanding of machines. We also present the torque computing equation which was not presented in the 1950 paper. For validation, we rely on electromagnetic transient (EMT) simulation, to design experiments, produce time-domain data, carry out fast Fourier transform (FFT) analysis for harmonic analysis, and produce torque-speed curves to verify the analysis results.