On an Estimate of the Rotor Winding Temperature at Start-up of High-voltage Induction Motors

This paper is devoted to research of start-up modes of high-voltage induction motors. To reduce a voltage dips during start of such motors, soft starters based on thyristor voltage converters are widely used. Acceleration of high inertia drives with a long start-up mode can be accompanied by rotor winding overheating. The authors analyze possibilities for estimate of rotor winding overheating during start-up. Analytical expressions for energy dissipated in the rotor winding at start-up are obtained. Having solved the Fredholm integral equation, the authors derive expressions allowing estimate of heat dissipation from the rotor during start-up. Calculation results of analytical expressions are tested with an integrated model that includes all elements of the power network. The adiabatic approach to the assessment of the maximum winding temperature at starting modes excluding heat transfer into the environment is proved to result in a substantial error. Analytical expressions allowing an approximate account of an uneven temperature distribution along the winding rotor are obtained.