| Abstract |
A current source inverter is widely used to drive an AC motor, because the inverter has many advantages, such as full four quadrant regenerative capability, and short circuit proof capability. However, a conventional autosequentially commutated current source inverter (ASCI) needs a long commutation delay time. Therefore, the upper limit of an operating frequency is relatively low. And also, existence of many commutation capacitors makes the inverter larger and less efficient. For this reason, we (Matsuse, Hashimoto, Kubota, Ree, 1983, 1985) proposed a new current source inverter, which uses gate turn-off thyristors (GTO) in the main circuit and does not need essentially commutation delay. The reactive power in a load is stored into a capacitor temporally, and then it is discharged into the DC circuit. This method of treating the reactive power is applied to the conventional ASCI to make the voltage spike lower in a commutation (Cho and Park, 1981; Palaniappan, 1982). In the case of the proposed inverter, commutation characteristics are variable according to the discharging period, that is, the capacitor voltage. The proposed inverter is able to drive an induction motor at a higher frequency than conventional current source inverters. Therefore, we must investigate the high frequency characteristics of the proposed current source inverter-fed induction motor drive. In this paper, the characteristics of the inverter, especially commutation characteristics, are described on the basis of the analysis and experimental results. |
