Rotor Speed Determination of Induction Machines using End Ring Leakage Flux Measurement

In this paper the end winding leakage field of an induction machine (IM) is analyzed with focus on usability of the rotor slot field harmonics for rotor speed determination. Starting from an analytical model based on Biot–Savart’s law, frequency and amplitude of the rotor slot harmonics in the rotor end ring leakage flux density are estimated. These are compared with results from 3D FEA. Both FEA simulation and analytical results are validated by means of measurements on an induction machine. The constraints of usability for rotor speed measurement considering the IM’s operating range are determined. All analytical, numerical and experimental results are based on a demonstrator machine for an automotive drive.