The accommodation of Electric Propulsion and the associated Power Processing Units (PPU) within a Spacecraft must lead to an integrated system providing full function and performance. An important aspect is the grounding of the electric propulsion system. It affects not only the performance of the electric propulsion (EP) system, moreover it affects the electrical charging potential of the spacecraft and can imply interactions with the solar generator. In practice different grounding schemes have been implemented in recent and planned spacecraft with electric propulsion: fixed ground and floating EP ground. Both have impact on the design of the PPU, as both provide different level of electrical stress to the PPU and to the thruster. The grounding may improve or degrade the performance of the thruster, especially if more than one thruster is operated simultaneously. In general it is advantageous to design a PPU with a floating ground system, especially if a mission type and/or the thruster design is new, as the PPU with floating ground can be easily converted into a fixed grounded unit, the reverse will invariably require a significant redesign effort.
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