SYNTHETIC LOADING OF 3-PHASE INDUCTION-MOTORS USING MICROPROCESSOR-CONTROLLED POWER ELECTRONICS

The paper describes methods of loading three-phase induction motors, w ithout the need to connect a load to the machine's drive shaft. Two me thods are described, one method uses microprocessor controlled power e lectronics to replace the electrical machines of an existing equivalen t load technique. The second method uses microprocessor controlled pow er electronics to rapidly modulate the machine's supply frequency. Bot h methods have the advantage of being extremely simple to set up and o perate, and enable vertical motors to be tested in the same way as hor izontal ones. The various power losses and their distribution in the m achine during synthetic loading are calculated taking into account rot or parameter variations with frequency. If full load temperature rise is measured using the two methods described, results are obtained whic h are close to, but always higher than, those measured when using a co nventional generator load and a 50 Hz inverter supply.