The operation of loads for over one hour. The ration of the useful work performed and the energy expended in producing it. Term used to describe the motor housing. Open Drip Proof, housing has openings in end shields and shell to allow air to cool the motor. Totally Enclosed Fan Cooled, housing has no openings.
Motor is cooled by an external fan on the non-drive end of the motor shaft.
Normally used in dirty, oily or damp applications. Totally Enclosed Non-Ventilated. Not equipped with an external cooling fan, depends on convection air for cooling. Totally Enclosed Air Over. Air flow from the driven or external device provides cooling air flow of the motor.