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)
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.
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)
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.
4. Totally Enclosed Air Over (TEAO)
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:
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.
Explosion proof motors are designed, manufactured and tested under the rigid requirements of the Underwriters Laboratories.
7. Hazardous Location (HAZ)
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 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.
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.