Operation and Performance of a Power Processing Unit for Inductive Pulsed Plasma Thrusters Operating at High Repetition Rates

Abstract

A highly modular prototype power processing unit (PPU) based on a paralleled boost converter design has been developed for recharging the capacitor bank of inductive pulsed plasma thrusters (IPPTs) operating at pulse rates of 1–10 kHz. Operation at these rates, which are one to two orders of magnitude higher than in previous designs, has been hypothesized to allow for efficient quasi-steady thruster operation while also improving lifetime and reliability. Benchtop testing of a prototype unit has demonstrated successful operation at pulse rates from 1 to 10 kHz, voltage gain as high as 25.5, power handling of 1–9.1 kW, and electrical efficiency up to 70%. Quasi-steady operation has been achieved up to 20 pulses, and the design has been shown to maintain functionality in the event of a simulated component failure. Theoretical and circuit simulator models of the prototype were developed and leveraged to identify the dominant loss mechanisms. The efficiency was determined to be primarily constrained by high switching losses, which were estimated to account for over 70% of total unit losses in the cases investigated. Scaling laws for the efficiency of the design were developed using simple linearized circuit equations, and indicated thruster performance was primarily dependent on the ratio of the input and output voltages, the inductive recapture ratio of the thruster, and the ratios of the relevant charging and switching timescales.