Silicon Carbide Power Processing Unit for Hall Effect Thrusters
- Created: Thursday, 31 July 2014
Prototype achieved 96.5% peak efficiency.
John H. Glenn Research Center, Cleveland, Ohio
A high-efficiency, rad-hard, 3.5-kW SiC power supply was developed for the power processing unit (PPU) of Hall effect thrusters. This work specifically targets the design of a PPU power supply for the HiVHAC (High Voltage Hall Accelerator) thruster. The PPU power supply under development utilizes components that were irradiated under TID (total ionizing dose) conditions to greater than 3 Mrad with little to no change in device performance.
The proposed PPU power supply will significantly increase power density by more than five times over the present system (> 2.5 kW/kg target), and will offer a significantly enhanced dynamic power/voltage range, which is especially important in optimizing future Hall thruster engine efficiency. The goal is to provide a constant stable power output of 1.2 kW per module (or 3.5 kW per system PPU) across the output voltage range of 200 to 700 V. A new realization of a pull-pull was selected for implementation. This new approach utilizes a resonant switching cell to achieve soft-switching operation, boosting converter efficiency.
The devices were utilized to develop a novel resonant switch cell topology capable of reducing the power converter’s switching loss by up to 4.3×. The switch cell topology utilizes a saturable resonant inductor to reduce the size and power loss of the cell. Additionally, the cell transfers energy stored in the inductor into a capacitor for efficient energy storage during the cell’s conduction cycle. This energy is then transferred back to the system when the cell turns off, thus reducing the total switching energy.
The PPU power supply prototype achieved 96.5% peak efficiency (>96.0% on 9 of 13 throttle points), 18.8 W/in.3 (≈1.15 W/cm3 ) volumetric power density, 32.5 W/in.2 (≈5 W/cm2) areal power density, and 2.33 kW/kg gravimetric power density. The gravimetric power density goal was slightly under the specification (by <7%), though this was determined to be an acceptable compromise due to increased efficiency.
This work was done by Bradley Reese, Chris Hearn, Chad O’Neal, and Washington Cilio of Arkansas Power Electronic International for Glenn Research Center.
Inquiries concerning rights for the commercial use of this invention should be addressed to NASA Glenn Research Center, Innovative Partnerships Office, Attn: Steven Fedor, Mail Stop 4–8, 21000 Brookpark Road, Cleveland, Ohio 44135. Refer to LEW-19116-1.