| MOTOR ENCLOSURES |
The type of enclosure required is dependent upon the surrounding atmosphere in which the motor is installed
and the amount of mechanical protection and corrosion resistance required. The two general classes of motor
enclosure are open and totally-enclosed. An open machine is one having ventilating openings which permit
passage of external air over and around the winding of the motor. A totally-enclosed machine is constructed
to prevent the free exchange of air between the inside and outside of the motor, but not sufficiently enclosed
to be termed air-tight.
Derivatives of these two basic enclosures are described below.
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| DRIPPROOF |
| Dripproof motors are designed to be internally ventilated by ambient air, having ventilation openings
constructed so that successful operation is not affected when drops of liquid or solid particles strike the
enclosure at any angle from 0 - 15 degrees downward from vertical. Dripproof motors are typically used in
relatively clean, indoor applications. |
| WEATHER PROTECTED TYPE I (WPI) |
| A weather protected type I machine is an open machine with its ventilating passages so constructed as to minimize the entrance of rain, snow and airborne particles to the electric parts and having its ventilating openings so constructed as to prevent the passage of a cylindrical rod 3/4-inch in diameter. |
| WEATHER PROTECTED TYPE II (WPII) |
| A weather protected type II machine shall have, in addition to the enclosure defined for a weather protected type I machine, ventilating passages at both intake and discharge so arranged that high-velocity air and airborne particles blown into the machine by storms or high winds can be discharged without entering the internal ventilating passages leading directly to the electric parts of the machine itself. For motors in frames 182T through 449T, standard TEFC motors should be specified. Ratings built in frames 509 and larger utilize dripproof frames with "top hat" mechanical construction to meet the above specifications. WPII motors have provisions for air filters. |
| TOTALLY-ENCLOSED |
Totally-enclosed motors are designed so that there is no free exchange of air between the inside and the outside of the enclosure, but not sufficiently enclosed to be airtight. Totally-enclosed motors may be of three basic types of construction.
1. TEFC (Totally-Enclosed Fan-Cooled) This type includes an external fan mounted on the motor shaft. This fan is enclosed in a fan casing which both protects the fan and directs the output air over the motor frame for cooling.
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2. TEAO (Totally-Enclosed Air-Over) This type is similar to TEFC designs except the the cooling air being forced over the motor frame is provided by a fan which is not an integral part of the motor.
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3. TENV (Totally-Enclosed Non-Ventilated) This type of construction does not require forced airflow over the motor frame for cooling.
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4. TEBC (Totally-Enclosed Blower Cooled) is used in applications where a separate mounted blower provides supplementary air to cool the motor. Typical uses are in inverter drive application with low frequency.
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