A constant frequency ac power supply is developed using a new current Source inverter (CSI). In the new CSI, we used three capacitors at the three phase ac output terminals to absorb high voltage spikes which usually occur when thyristor current is interrupted during the commutation process in CSI. By the role of the capacitors, no additional voltage clamping circuit is required and the ratings of commutation capacitors and thyristors are reduced considerably compared with those of the conventional auto-sequential commutated inverter (ASCI).
Furthermore, these capacitors also provide smooth and close to sinusoidal output waveforms without requiring additional filter network. Together with the capacitors, L-C ring around circuits are connected to respective thyristors to provide fast commutation almost independent of load condition. By the operation of the ring around circuit, high frequency pulsewidth modulation (PWM) is achieved in the new CSI.
In addition to the 3-phase CSI, we also developed a new single-phase inverter system. In the new single-phase CSI, we achieved very good reliability in commutation as well.
In all, these systems are proved to be suitale for high power ac supply systems.
