1990-09-01

Application of a Fault Tolerant Electrical Power System 901803

The Fault Tolerant Electrical Power System (FTEPS) Air Force program conducted by Boeing concluded that future electrical systems can be designed to meet the stringent requirements of fly-by-wire and power-by-wire equipment on aircraft. A power system architecture was designed and implemented in a ground demonstrator that provides electrical power to flight-critical loads after three major system faults, provides electrical power to mission-critical loads after two major system faults, and provides electrical power to non-flight/mission critical loads after one major system fault. In addition, the system provides electrical power to the load buses that is 100 times more reliable than the typical loads on those buses.
The FTEPS design is based on the ability of the system to manage the system loads by optimizing the distribution of the available source capacity. To accomplish this, a distributed control system was designed that includes the MIL-STD-1750A-based power system processors (PSP) and the electrical load management centers (ELMC). Primary system control is allocated to the two system PSPs, which communicate instructions to the ELMCs via dual redundant MIL-STD-1553B data buses. Electrical power is distributed through the ELMCs by means of solid state power controllers (SSPC), which provide fault protection and load control. Primary ac power is provided by four 60-kVA (variable-speed constant frequency) generators, and dc power is provided by four transformer-rectifier units with uninterruptible dc power provided by two sealed lead-acid batteries. This paper describes these unique features of FTEPS and their application to future aircraft.

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