Fast Solution of Rotor Losses in Inverter-Fed Cage Induction Motors with Skewed Slots

The conventional calculation of rotor losses in cage induction motors by time-stepping finite element method needs a full slip-cycle calculation of the rotor flux density and the bar current density waves to include the effect of fundamental and harmonic components. This calculation is extremely expensive in CPU time when handling motors with skewed slots and inverter supply. This paper proposes a technique that reproduces the full slip-cycle waves by utilizing both the time-varying and the spatial information of the rotor electromagnetic quantities so that the CPU time of the simulation can be saved significantly. The more rotor bars per pole pair the induction motor has, the less CPU time the simulation needs. The proposed technique is adopted for the rotor losses of a 5.5-kW induction motor, and the results are compared for validation with those obtained by the conventional method and by a test.