1400 A, +/-900 V peak pulse switch mode power supplies for SNS injection kickers

This paper describes simulation and experimental results for a 1400 A, ±900 V peak rated, switch mode power supply for SNS Injection Kicker Magnets. For each magnet (13 mΩ, 160 μH), the power supply must supply controlled pulses at 60 Hz repetition rate. The pulse current must rise from zero to maximum in less than 1 millisec in a controlled manner, flat top for up to 2 millisec, and should fall in a controlled manner to less than 4 A within 500 μs. The low current performance during fall time is the biggest challenge in this power supply. The simulation results show that to meet the controlled fall of the current and the current ripple requirements, voltage loop bandwidth of at least 10 kHz and switching frequency of at least 100 kHz are required. To achieve high power high frequency switching with IGBT switches, a series connected topology with three phase shifted (0°, 60° & 120°) converters each with 40 kHz switching frequency (IGBT at 20 kHz), has been achieved. In this paper, the circuit topology, relevant system specifications and experimental results that meet the requirements of the power supply are described in detail. A unique six pulse SCR rectifier circuit with capacitor storage has been implemented to achieve minimum pulse width to meet required performance during current fall time below 50 A due to the very narrow pulse width and nonlinearity from IGBT turn-on/off times.