Starting torque analysis in skewed-cage induction motor with broken bar using a combined hybrid analytical/finite element technique

The aim of this paper is to analyze the positional variation of starting torque in a 3-phase induction motor. This can depend on different factors: manufacture of the rotor (fabricated or cast), skewing of the rotor bars, broken bars (and position of the break), rotor eccentricities, and other possible asymmetries. In the study, different rotors are experimentally tested and a hybrid analytical/finite element technique is developed for rapid assessment of the starting torque variation with rotor position. This technique allows for rotor skew, broken bars and rotor eccentricity. Simulation results are presented to illustrate the method and critically compared to the experimental measurements. The method is shown to be effective in modelling the parasitic permeance effects due to slotting and asymmetries. The experimental measurement of the starting torque at different rotor positions could be utilized as an off-line diagnostic tool and as a quality control test in the manufacturing process.