Compact design of a 30 kV rapid capacitor charger

This paper describes the downsizing potential of a power supply for charging a 7.2μF capacitor to a voltage of 30kV, which represents 3.24kJ of energy, in approximately 40ms. This process should be repeatable 10-20 times in a short burst mode within a time frame of a few minutes. The primary supply is a DC source with approximately 650V. A previous design achieved all these goals using 4 Semikron half-bridge IGBTs rated at 1200V/1200A each [1,2]. From the operational experience with the previous charger we concluded, that the weight and volume of the inverter, which is the core of the system, can be reduced to half of the previous size. This can be achieved by using advancements in IGBT modules as well as state of the art capacitors and optimum packaging. Due to the increased capabilities of the new IGBT modules, the number of required modules can be reduced from 4 to 2. In addition, the 15V/10A auxiliary power supply, which was previously required, is no longer needed, since the new modules derive their auxiliary power from the main DC bus. The new IGBT modules will be connected to form an H-Bridge. A step-up transformer and a rectifier bank will be connected to the output of the H-Bridge. For compactness, the cooling fins on the old modules have been removed, which was permissible due to the fact that the supply is only operated in short term burst mode. There are no cooling fins to remove on the new module since we are using the water-cooled version. This also gives us the option to water cool if needed. With these modifications, the original charger, which took up a standard 19 inch equipment rack, could be reduced to the size of an oversized suitcase.