In aircraft, power generating through anteaters, output is 115V AC three phase at 400Hz to 800Hz. Then auto transformer rectifier unit will convert this power to 270VDC bus distributed over the aircraft. Most of the equipment will consume power from 270VDC bus. Some equipment required 28VDC, so converting from 270VDC to 28VDC as DC to DC converter. This is the overall view f aircraft power distribution system
Auxiliary power unit (APU) is an additional energy source normally used to start the engines. ram air turbine also is available as backup power in flight in the unlikely event of a power failure.