– Defines the motor construction according to environmental protection and method of cooling. Types include:
- Open – A motor that has openings, which permit passage of external cooling air over and around the windings. Usually used indoors, in fairly clean locations.
- Open Dripproof (ODP) – Ventilation openings are so constructed that successful operation is not interfered with when drops of liquid or solid particles strike or enter the enclosure at any angle from 0 to 15 degrees downward from vertical.
- Weather-Protected Type I (WPI) – Ventilation passages are so constructed as to minimize the entrance of rain, snow and air-borne particles to the electric parts.
- Weather-Protected Type II (WPII) – In addition to the enclosure defined for a Weather-Protected Type I motor, its ventilating passages at both intake and discharge are so arranged that high velocity air and air-borne particles blown into the motor by storms or high winds can be discharged without entering the internal ventilation passages leading directly to the electrical parts of the motor.
- Totally Enclosed – A motor, which is enclosed to prevent the free exchange of air between the inside and outside of the motor, but not sufficiently enclosed to be termed airtight. Air and dust does not enter in sufficient quantity to interfere with satisfactory operation of the motor. Used in locations, which are dirty, damp and oily, etc.
- Totally Enclosed Fan Cooled (TEFC) – A frame-surface cooled motor equipped for self exterior cooling by means of a fan or fans integral with the motor but external to the enclosing parts.
- Totally Enclosed Non-ventilated (TENV) – A frame-surface cooled motor which is only equipped for cooling by free convection. Not equipped with an external cooling fan.
- Totally Enclosed Air-Over (TEAO) – A frame-surface cooled motor intended for exterior cooling by a ventilating means external to the motor.