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NEMA Enclosure Standards for Electric Motors

NEMA enclosure standard for electrical motors.

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The enclosures of electrical motors are standardized by NEMA (National Electrical Manufacturers Association) as:


Ventilation openings in shield and/or frame prevents drops of liquid from falling into motor within up to 15 degree angle from vertical.

Designed for reasonably dry, clean, and well ventilated (usually indoors) areas. Outdoors installation require the motor to be protected with a cover that does not restrict the flow of air to the motor.

Totally Enclosed Air Over (TEAO)

Dust-tight fan and blower motors for shaft mounted fans or belt driven fans. The motors mounted within the airflow of the fan.

Totally Enclosed Non-Ventilated (TENV)

No ventilation openings, enclosed to prevent free exchange of air (not airtight). No external cooling fan, relies on convection cooling.

Suitable where the motor is exposed to dirt or dampness. Not suited in very moist humid or hazardous (explosive) air.

Totally Enclosed Fan Cooled (TEFC)

Same as TENV with an external fan as an integral part of the motor. The fan provides cooling by blowing air on the outside of the motor.

Totally Enclosed, Hostile and Severe Environment

Designed for use in extreme conditions - moist and/or chemical environments. Not for hazardous locations.

Totally Enclosed Blower Cooled

Same as TEFC with external fan on a power supply independent of the inverter output. Full cooling even at lower motor speeds.

Explosion-Proof Motors

The motor ambient temperature shall not exceed +40oC. Motors are approved for the classes:

CLASS I (Gases, Vapors)

  • Group A - Acetylene
  • Group B - Butadiene, ethylene oxide, hydrogen, propylene oxide
  • Group C - Acetaldehyde, cyclopropane, diethel ether, ethylene, isoprene
  • Group D - Acetone, acrylonitrite, ammonia, benzene, butane, ethylene dichloride, gasoline, hexane, methane, methanol, naphtha, propane, propylene, styrene, toluene, vinyl acetate, vinyl chloride, xylem

CLASS II (Combustible Dusts)

  • Group E - Aluminum, magnesium and other metal dusts with similar characteristics.
  • Group F - Carbon black, coke or coal dust
  • Group G - Flour, starch or grain dust

CLASS III (Fibers and flyings)

  • Group G - Flour, starch or grain dust
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