Posted on May 2nd, 2018
An auxiliary power unit (APU) is a device on a vehicle that provides energy for functions other than propulsion. They are commonly found on large aircraft, as well as some large land vehicles. Aircraft APUs generally produce 115V at 400 Hz (rather than 50/60 Hz in mains supply), to run the electrical systems of the aircraft; others can produce 28V DC. APUs are also present on naval ships. APUs can provide power through single or three-phase systems.