Analysis of Indirect Temperature-Rise Tests of Induction Machines Using Time-Stepping Finite Element Method

The ability to test the temperature rise of induction motors with indirect loading is very useful for the motor industry. In this paper different indirect loading schemes-including two-frequency methods, phantom loading methods, and inverter driven methods are analyzed. Their merits and drawbacks are highlighted. A universal method for analyzing all of these indirect temperature-rise methods is presented. The analysis is based on the time-stepping finite element model of skewed rotor bar induction machines, and the solution can include the effects of saturation, eddy-current, and the high-order harmonic fields directly. The computed losses can also include the stray losses due to the high-order harmonic fields. An 11 kW induction motor, when operating with normal full load and on phantom loading, has been used to verify the computed results.