Development of a Modular Hall Thruster Power Converter

Abstract

Aerojet has completed the development and qualification of a 4.5 kW Hall thruster system to serve GEO satellite applications for station keeping and orbit raising as well as for use as primary propulsion on NASA missions. This 4.5 kW Hall thruster system is currently in use on the Air Force’s first Advanced Extremely High Frequency (AEHF) satellite. The system includes the BPT-4000 Hall thruster, Power Processing unit (PPU), Xenon Flow Controller (XFC) and associated electrical harnessing. Hall thruster technology is applicable to a wide range of missions that will employ a variety of power systems and as such Aerojet and the Jet Propulsion Laboratory (JPL) have identified the need to develop a scalable power converter that can be tailored to a given application. The envisioned PPU architecture will be able to function over a wide input voltage range (~2:1), provide efficient throttling over a wide output range (100s of Watts – 10s of kilowatts), and employ a robust topology capable of meeting stringent radiation, derating, and component quality requirements. As an added benefit, a modular power converter will reduce the development time and cost for the next generation of PPUs that will be needed to serve applications requiring variable input voltages, higher output power, and a wider power and voltage throttling range. The modular power converters are capable of accepting unregulated 70-140 V input voltages with an output voltage range of 150-400 V when operated in parallel or 150-800 V when operated in series. A full bridge, phase-shifted, zero voltage switching topology was selected as the most suitable for satisfying the wide input and output range. Two converters were fabricated to demonstrate the individual capability of the module as well as the stacked capability of modules working in series or parallel configurations. Converter power efficiency was measured over the full input and output voltage range. Peak efficiencies meeting the target of 94% were measured. Testing under parallel operation of the converters demonstrated current sharing while series operation demonstrated the full 800 V output capability. Demonstration of these power modules retires the major risk associated with converting Aerojet’s existing regulated PPU technology to an expanded architecture compatible with NASA missions and a variety of commercial platforms.