New Method to Scale down an Operation of a Large Accelerator Power Supply

The pulse operation of an accelerator required large dynamic range of operation in a power supply. The demanded power at injection is only 0.2 % of full rating. This is conventionally obtained by changing ignition angles of thyristors otherwise by switching a small number of unit supplies in a large number of which the total power supply is composed of. The former case generates a large amount of ripples in D. C. current. At KEK accelerator the main power supply is composed of three units one of which is served for injection with new method. The new method is combination of a converter and an inverter. Two thyristor bridges have just same rating but the operation modes are opposite. The output voltages of such converter and inverter are mutually cancelled and the resultant output voltage is equivalent to one which is scaled down by only the ignition angle. The operation of such system has shown good performance properties with regard to power factor and ripples in D. C. current. The new method saved D. C. filters and dynamic filters in KEK accelerator.