SSPC Technologies for Aircraft High Voltage DC Power Distribution Applications 2012-01-2213

There is a growing need for high voltage direct current (HVDC) power distribution systems in aircraft which provide low-loss distribution with low weight. Challenges associated with HVDC distribution systems include improving reliability and reducing the size and weight of key components such as electric load control units (ELCUs), or remote power controllers (RPCs) for load control and feeder protection, and primary bus switching contactors. The traditional electromechanical current interrupting devices suffer from poor reliability due to arcs generated during repeated closing and opening operations, and are generally slow in isolating a fault with potentially high let-through energy, which directly impacts system safety.

Solid State Power Controller (SSPC) technology has gained acceptance as a modern alternative to electromechanical contactors and circuit breakers, due to its high reliability, “soft” switching characteristics, fast response time, and ability to facilitate advanced load management and other aircraft functions. While SSPCs with current rating of less than 20A have been widely used in aircraft secondary distribution systems, replacing thermal circuit breakers, their application for aircraft HVDC primary power distribution systems requires further technology maturation. This paper presents systematic solutions to the potential problems and challenges associated with the use of SSPCs in aircraft HVDC power distribution, such as excessive power dissipation as a result of high voltage drop across the SSPC, leakage, “fail shorted”, nuisance trips due to lightning strikes, and high inrush currents to capacitive loads. Test results based on a 270VDC, 120A SSPC prototype are also presented.