7 Most Common Motor Enclosure Types Defined By NEMA Standards

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.

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)

Premium Efficient Super-E motor with Open Drip Proof (ODP) construction by BALDOR

Premium Efficient Super-E motor with Open Drip Proof (ODP) construction by BALDOR


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)

Weg NEMA Premium Efficiency - Three Phase TEFC Motors

Weg NEMA Premium Efficiency - Three Phase TEFC Motors


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.

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.


3. Totally Enclosed Non-Ventilated (TENV)

DAYTON DC Motor, PM, TENV, 1/3 HP, 1800 rpm, 24VDC

DAYTON DC Motor, PM, TENV, 1/3 HP, 1800 rpm, 24VDC


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)

US Motors - Refrigeration Duty TEAO Motor, 1/2 HP, 3-Phase, 1140 RPM Motor

US Motors - Refrigeration Duty TEAO Motor, 1/2 HP, 3-Phase, 1140 RPM Motor


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)

Baldor's Washdown Duty Motor

Baldor's Washdown Duty Motor for food processing, packaging, pharmaceuticals, or applications where motors are regularly exposed to high pressure wash down.


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:

Designed for use in extremely moist or chemical environments, but not for hazardous locations.

6. Explosion-proof enclosures (EXPL)

SIEMENS's explosion proof motor for hazardous environments

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.


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.

Explosion proof motors are designed, manufactured and tested under the rigid requirements of the Underwriters Laboratories.


7. Hazardous Location (HAZ)

Motor 3-Phase, 5 HP - to Power Fans, Blowers, Pumps or Air Compressors in Areas That Meet the National Electrical Code for Hazardous Locations

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

  • 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.


author-pic

Edvard - Electrical engineer, programmer and founder of EEP. Highly specialized for design of LV high power busbar trunking (<6300A) in power substations, buildings and industry fascilities. Designing of LV/MV switchgears. Professional in AutoCAD programming and web-design. Present on Google+.



2 Comments


  1. Ashok Parikh
    Aug 12, 2013

    Dear Edvard,

    I am unable to download your highly informative articles relevant to induction motors. Can you be of any help.

    Regards,
    Ashok Parikh


    • Edvard
      Aug 12, 2013

      Hi Ashok,

      I’m working on it, I know that there is a problem. printfriendly.com has changed something, and now print in PDF don’t work.

      It will be fixed soon!

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