Ground Power Unit (GPU) is a power supply equipment that provides power to aircraft while on the ground, commonly referred to as ground power or external power. Typically, there are two types: ground power carts and fixed power sources.
During most of the time on the ground, aircraft operations require power. Ground power can be generated by an electric motor-generator set, where the prime mover drives one power source, providing electrical power to the aircraft's power outlets.
The standard for ground power is typically three-phase 400Hz 115VAC, which is the same as the power provided by aircraft generators. In some instances, usually at major airports, electrical conversion devices near the aircraft entry points supply three-phase 115V AC power that has been converted and obtained from the power grid.
