The Pulsed Power Physics Branch at the U.S. Naval Research Laboratory (NRL) is developing a battery-powered, rep-rate charger for a 60-kJ capacitor bank. The goal is to charge a 4800μF capacitor to 5kV in five seconds for a fifty shot burst. A bank of LiFePO4 batteries is used with a full H-bridge converter and transformer to elevate the 500V battery voltage to a 5kV secondary voltage. The operation of the Integrated Gate Bipolar Transistor (IGBT) generates heat as a byproduct of the energy transfer from the batteries to the capacitor, which must be effectively removed. The traditional method of cooling the IGBTs involves a passive heat sink and forced air cooling, which can be quite large if the dissipated power load is high enough. This work investigates the replacement of the forced air cooling method with an oscillating heat pipe (OHP). The OHP investigated herein was made of aluminum with dimensions of 130.1 mm × 101.9 mm × 2.5 mm. The OHP channel dimension imbedded in the aluminum block is 1.0 mm by 1.0 mm. Utilizing high effective thermal conductivity, the integrated OHP has the potential to reduce the overall system volume and enable the design of a sealed converter package. Numerical analysis and experimental results demonstrate that the OHP can significantly increase the effective thermal conductivity and enable a fast time response of the pulsed power DC-DC converter. Comparison with the numerical analysis show that the heat transfer resistance occurring in the cooling block is the primary resistance for the investigated IGBT OHP cooling.
