Date of this Version
A. Toftul, "Characterization and testing of a 5.8 kV SiC PiN diode for electric space propulsion applications," M.S. thesis, Dept. Elect. Eng., Univ. of Nebraska-Lincoln, Lincoln, Nebraska, 2014.
Inductive Pulsed Plasma Thrusters (IPPTs) are a type of in-space propulsion that has multiple advantages over conventional chemical propulsion for long-duration, deep space missions. Existing IPPT prototypes utilize spark gap switches, however these are subject to corrosion problems that make them unreliable for long-term use. Recent advances in solid state switching technology have opened up a variety of switching options that could provide greater reliability, controllability, and increased energy efficiency. Taking advantage of this, a novel thruster drive circuit topology containing a high-power silicon controlled rectifier (SCR) and series fast recovery diode (FRD) is proposed that is expected to increase the recapture efficiency of the thruster drive circuit, defined as the percentage of energy that remains on the capacitor bank following a single discharge cycle.
A conventional Si FRD from ABB and a prototype Silicon Carbide (SiC) PiN diode from Cree, Inc. were characterized and tested as part of an IPPT solid state switching module on the Flat-Plate Thruster (FPT) developed and constructed at the National Aeronautics and Space Administration (NASA) Marshall Space Flight Center (MSFC) Electric Propulsion Thruster Development Laboratory. Preliminary analytical characterization of the devices, including static performance, dynamic (switching) performance, and thermal analysis is described, as well as the construction of the FPT thruster and the experimental setup used for thruster switching data collection. Collected experimental data shows that the proposed drive circuit topology results in a 20% higher recapture efficiency as compared to a topology containing no series diode. In addition, the superior reverse recovery characteristics of the Cree SiC diode as compared with the ABB Si diode result in an additional gain in recapture efficiency of approximately 5% across a range of capacitor bank charge voltages.
Advisor: Jerry L. Hudgins