A proof-of-principle power converter for the Spallation Neutron Source RF system

The power converter for the SNS RF system is a fast pulsed power supply that transforms 7 kV, 3-phase AC input power into 120 kV pulses with an amplitude of 80 A, a flat-top pulse length of 1.1 ms, and a repetition rate of 60 Hz. The power converter accomplishes this transformation by rectifying the input power to 8 kV DC. This is followed by a high-frequency (20 kHz) switched mode DC-to-DC converter that has rise and fall times below 0.1 ms. (The required peak power for a pair of 2.5 MW/805 MHz klystrons is almost 10 MW, and the average power is 750 kW). Since the peak and average power requirements are a significant advance of the state-of-the art for switched-mode power supplies, it is prudent to design and build a scale version of the circuit. This proof-of-principle version of the circuit is a 1/100th voltage model that operates with an input of 100 V and produces an output of 1200 V. The critical components of the converter are the IGBT switches and the high voltage transformer. The design of the low-power converter involved a novel high voltage transformer and the same switches that will be used in the high power converter. Simulations have been performed and data that shows agreement between the computer simulation and the scale model will be presented