ABSTRACT
This chapter reviews the various sources of electrical power used on aircraft and their typical applications. Aircraft electrical power can be derived from a variety of sources; these are categorized as either primary or secondary supplies. The basic power source found on most aircraft is the battery, delivering direct current (DC). The DC input voltage is applied to an oscillator that produces a sinusoidal output voltage. Generators can supply either direct or alternating current; the outputs of generators need to be regulated. Alternating current generators are also referred to as alternators. An auxiliary power unit (APU) is normally used for starting the aircraft's main engines via the air distribution system. In some aircraft, the APU can also provide electrical power in the air in the event of main generator failure. An APU is a relatively small gas turbine engine, typically located in the tail cone of the aircraft.
