Synthetic loading of three-phase induction motors using microprocessor controlled power electronics

The paper describes methods of loading three-phase induction motors, without the need to connect a load to the machine´s drive shaft. Two methods are described, one method uses microprocessor controlled power electronics to replace the electrical machines of an existing equivalent load technique. The second method uses microprocessor controlled power electronics to rapidly modulate the machine´s supply frequency. Both methods have the advantage of being extremely simple to set up and operate, and enable vertical motors to be tested in the same way as horizontal ones. The various power losses and their distribution in the machine during synthetic loading are calculated taking into account rotor parameter variations with frequency. If full load temperature rise is measured using the two methods described, results are obtained which are close to, but always higher than, those measured when using a conventional generator load and a 50 Hz inverter supply