A 208Y/120-volt 120-ampere three-pole 400-cycle electrically operated aircraft circuit breaker

With the selection of the 208Y/120-volt three-phase 400-cycle a-c system by the Army Air Forces for large aircraft, there has arisen the need for appropriate switchgear. In order to be applicable to the electric systems of such planes, switchgear must be able to perform its normal and emergency functions under the encountered conditions of temperature, pressure, humidity, vibration, and acceleration. This paper describes a 120-ampere remotely controlled electrically operated air circuit breaker designed for use as a bus sectionalizing, ring tie, or generator breaker on the 400-cycle grounded-neutral system. The interrupting rating of this breaker is 3,800 amperes at all pressures from sea level to 50,000 feet altitude. The closing solenoid and shunt trip coils have been designed to operate over a wide range of ambient temperature and control voltage. Weight and size, being primary considerations in aircraft equipment, have been held to a minimum.