The CSI fed induction motor drive has good features that the power circuit is rugged and reliable. On the contrary, it has limitations that operating frequency range is somewhat lower, the large size of the dc link inductance and commutation capacitors make the system somewhat bulky and expensive and the problem of torque ripple is caused by the six-stepped current. Due to the results of some noticeable researches the first two problems can be improved to a large extent. For the reduction of torque ripple, there are two methods known as pulse width modulation and dc link current modulation. In this thesis, the two methods are carefully examined and dc link current modulation method is adopted. On the other hand, phase controlled rectifier has been used for the modulation of dc link current and there is a limitation that modulation becomes difficult for the stator frequency of above about 5Hz. This limitation stems from the fact that the bandwidth of the phase controlled rectifier is about 30Hz. Instead of phase controlled rectifier, chopper and hysteresis comparator pair using reference current wave is proposed. As a result, the system bandwidth of the current modulation part can be easily improved to the extent of several kHz and the above problem can be solved.
