Iron losses under voltage excitation by novel and classical frequency converters

Iron losses due to flux harmonics in stator cores of Pulse-Width-Modulation [PWM] back -to-back inverter-fed induction motors have a major effect on system efficiency. A new generation of direct ac-ac matrix converters offer important advantages over classical frequency converters such as absence of bulky and temperature sensitive dc-links and possible adjustment of power factor. The paper presents experimental results of magnetic losses in three nonoriented electrical steels magnetised under different types of voltage excitation. Characteristic waveforms of real 3x3 matrix converter and PW inverter under various modulation indices were recorded and used by a signal generator feeding a Single Strip Tester [SST] used to measure iron loss. Harmonic distortion, contribution of high frequency components and sideband effect were analysed. Influence of flux density curve as well as form factor of voltage excitation were also investigated.