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Motor enclosures
An enclosure protects a motor from contaminants in the environment in which it is operating. In addition, the type of enclosure affects the cooling of the motor. Enclosures are categorized as either open or totally enclosed, and there are different types of enclosures within each category.
Open drip proof (ODP)
Open enclosures permit cooling air to flow through the motor. The rotor has fan blades that help move the air through the motor. One type of open enclosure is the ODP enclosure. In an ODP enclosure, the vent openings prevent liquids and solids that fall from above at angles up to 15° from vertical from entering the interior of the motor and damaging the operating components. When the motor is not in the horizontal position, such as when it is mounted on a wall, a special cover might be necessary to protect it. An ODP enclosure can be specified when the environment is free from contaminants and where wind-driven rain is not a consideration.
Totally enclosed nonventilated (TENV)
Sometimes, the air surrounding the motor contains corrosive elements, dust, sand, and other debris that can damage the internal parts of a motor, or the motor is exposed to wind-driven rain or seawater spray. A totally enclosed motor enclosure is not airtight, but it restricts the free exchange of air between the inside of the motor and the outside. A seal where the shaft passes through the housing keeps out water, dust, and other foreign matter that could enter the motor along the shaft. The absence of ventilating openings means that all heat dissipates through the enclosure through conduction.
Most TENV motors are fractional horsepower in size. TENV motors can be used indoors and outdoors.
Totally enclosed, fan cooled (TEFC)
Totally enclosed, fan-cooled enclosures are similar to TENV enclosures, except that an external fan is mounted opposite the drive end of the motor. The fan provides additional cooling by blowing air over the exterior of the motor to dissipate heat more quickly. A shroud covers the fan to prevent anyone from touching it. With this arrangement no outside air enters the interior of the motor. TEFC motors can be used in dirty, moist, or mildly corrosive operating conditions, or where wind-driven rain is anticipated.
Explosion proof (XP)
Explosion-proof motor enclosures are similar in appearance to TEFC motors, but are designed to contain an inside explosion and to prevent ignition of specified gases or vapors surrounding the motors.
References
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See also
Electrical distribution systems