This paper describes a large number of experiments comparingaudible noise, losses and efficiency of different induction motorssupplied by an IGBT inverter. The influence of the switching frequencyon the motor behaviour is analysed. As a comparison the motor is alsosupplied directly from the mains. Furthermore two different motors arecompared to study the influence of the rotor cage design on the motorbehaviour. It is shown that the choice of the switching frequency has alarge influence on the audible noise produced by induction motors. Bytaking higher switching frequencies, the time harmonics move to anonaudible region. At some higher switching frequencies subharmonicsappear, having a bad influence on the audible noise. At higherfundamental frequencies the audible noise of the fan dominates. Theswitching frequencies can cause pure tones that are very disturbing tothe human ear. The influence of the switching frequency on theefficiency is rather small. Minimal overall losses appear around 3 and 4kHz. The voltage-frequency ratio should be taken constant from the pointof view of the efficiency
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