7 Most Common Motor Enclosure Types Defined By NEMA
Standards
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8/9/2013
7 Most Common Motor Enclosure Types Defined By NEMA Standards (on photo: Louis Allis Pacemaker Premium NEMA motor – louisallis.com)
Important role of enclosure
The enclosure of the motor must protect the windings, bearings, and other mechanical parts from moisture,
chemicals, mechanical damage and abrasion from grit.
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NEMA standards MG1-1.25 through 1.27 define more than 20 types of enclosures under the categories of open
machines, totally enclosed machines, and machines with encapsulated or sealed windings.
The 7 most common types of enclosures are:
1. Open Drip Proof (ODP)
Allows air to circulate through the windings for cooling, but
prevent drops of liquid from falling into motor within a 15 degree
angle from vertical. Typically used for indoor applications in
relatively clean, dry locations.
2. Totally Enclosed Fan Cooled (TEFC)
Prevents the free exchange of air between the inside and outside of
the frame, but does not make the frame completely air tight. A fan
is attached to the shaft and pushes air over the frame during its
operation to help in the cooling process.
Premium Efficient Super-E motor with Open Drip Proof
(ODP) construction by BALDOR
The ribbed frame is designed to increase the surface area for
cooling purposes.
The TEFC style enclosure is the most versatile of all. It is used
on pumps, fans, compressors, general industrial belt drive and direct
connected equipment.
Total Enclosed Fan Cooled vs Open Drip Proof (TEFC
vs ODP)
Cant see this video? Click here to watch it on Youtube.
Weg NEMA Premium Efficiency – Three Phase TEFC
Motors
3. Totally Enclosed Non-Ventilated (TENV)
Similar to a TEFC, but has no cooling fan and relies on convention for cooling. No vent openings, tightly enclosed
to prevent the free exchange of air, but not airtight.
These are suitable for uses which are exposed to dirt or dampness, but not very moist or hazardous (explosive)
locations.
4. Totally Enclosed Air Over (TEAO)
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DAYTON DC Motor, PM, TENV, 1/3 HP, 1800 rpm,
Dust-tight fan and blower duty motors designed for shaft mounted
fans or belt driven fans. The motor must be mounted within the
airflow of the fan.
5. Totally Enclosed Wash down (TEWD)
Designed to withstand high pressure wash-downs or other high
humidity or wet environments. Available on TEAO, TEFC and
ENV enclosures totally enclosed, hostile and severe environment
motors:
24VDC
Designed for use in extremely moist or chemical
environments, but not for hazardous locations.
6. Explosion-proof enclosures (EXPL)
The explosion proof motor is a totally enclosed machine and is
designed to withstand an explosion of specified gas or vapor
inside the motor casing and prevent the ignition outside the
motor by sparks, flashing or explosion.
These motors are designed for specific hazardous purposes,
such as atmospheres containing gases or hazardous dusts. For
safe operation, the maximum motor operating temperature must
be below the ignition temperature of surrounding gases or vapors.
US Motors – Refrigeration Duty TEAO Motor, 1/2 HP, 3Phase, 1140 RPM Motor
Explosion proof motors are designed, manufactured and tested
under the rigid requirements of the Underwriters Laboratories.
7. Hazardous Location (HAZ)
Baldor’s Washdown Duty Motor for food processing,
packaging, pharmaceuticals, or applications where
motors are regularly exposed to high pressure wash
down.
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SIEMENS’s explosion proof motor for hazardous
environments, such as in chemical plants, the oil industry, in
gas works, in wood and plastic processing industry or in
agriculture.
Motor 3-Phase, 5 HP – to Power Fans, Blowers, Pumps or Air Compressors in Areas
That Meet the National Electrical Code for Hazardous Locations
Hazardous location motor applications are classified by the type of hazardous environment present, the
characteristics of the specific material creating the hazard, the probability of exposure to the environment, and the
maximum temperature level that is considered safe for the substance creating the hazard.
The format used to define this information is a class, group, division and temperature code structure as defined by
the National Electric Code (NFPA-70).
The following hazardous locations are defined:
1) CLASS I
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Group A: Acetylene
Group B: Butadiene, ethylene oxide, hydrogen, propylene oxide, manufactured gases containing more than
30ydrogen by volume.
Group C: Acetaldehyde, cyclopropane, diethyl ether, ethylene.
Group D: Acetone, acrylonitrile, ammonia, benzene, butane, ethanol, ethylene dichloride, gasoline, hexane,
isoprene, methane (natural gas), methanol, naphtha, propane, propylene, styrene, toluene, vinyl acetate, vinyl
chloride, xylene.
2) CLASS II
Group E: Aluminum, magnesium, and other metal dusts withsimilar characteristics.
Group F: Carbon black, coke or coaldust.
Group G: Flour, starch orgrain dust.
3) CLASS III
Easily ignitable fibers,such asrayon, cotton, sisal, hemp, cocoa fiber, oakum, excelsior and other materials of
similar nature.
The NEMA enclosure description is similar to the IEC Index of Protection (IP) code. The NEMA designations
are more descriptive and general, whereas the IEC IP codes are more precise and narrowly defined by a 2-digit
code, with the first digit defining how well protected the motor is from solid objects and the second digit describing
how well protected the motor is from moisture.
For example, a NEMA “OpenDrip Proof (ODP)” motor corresponds to an IP22 and a NEMA “Totally Enclosed”
motor corresponds to an IP54, a NEMA “WeatherProof” motor to an IP45, and a NEMA “Wash-Down” motor
toan IP55.
Reference: Understanding Motor Nameplate Information: NEMA vs. IEC Standards – Continuing Education and
Development, Inc.
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