Effect of Insulation Properties on the Field Grading of Solid Dielectric DC Cable

Conventional loading of induction motors is an ex- tremely difficult and expensive process for large machines.In those cases, full load losses and temperature rise can be estimated by means of equivalent loading methods, which provide an accurate altemative, without the need of a mechanical load applied to the shaft.This paper describes three such methods, all using a commercial PWM inverter.The methods examined are described in detail and the results of performed on a 10 hp induction motor are presented.A calorimetric measurement facility was used in order to ensure consistency of result comparison between the different methods, as well as high accuracy for total loss measurement.The measured values of losses and temperature rise, although marginally larger, are in good agreement with those ob- tained through conventional loading.