ActronAir MPW65 3-Pole 40-50A is a motor protection circuit breaker for 3-phase ActronAir commercial unit compressor and fan motor circuits rated 40-50A, providing adjustable overload protection, short-circuit protection, and manual start/stop capability in a single DIN-rail mounted device. Unlike a standard MCB, the adjustable overload setting on the MPCB must be set to the motor's full load current nameplate value before commissioning -- an incorrectly set overload provides inadequate motor protection. Isolate power at mains before replacing any motor protection circuit breaker.