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Large Industrial Electric Motor Specialists

Understanding NEMA Motor Enclosure Types

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Have you ever noticed the different types of enclosures that surround electric motors? The National Electrical Manufacturers Association (NEMA) has established over 20 different enclosure types under their MG1 standards, which categorize motors as open, totally enclosed, or sealed windings designs. These many NEMA-defined enclosure types cover motors for various operating environments, protection levels, and exposure to contact, debris, moisture and hazards. In this article, we’ll cover the most commonly used enclosure types, and teach you how to identify them based off of looks.

What Are Motor Enclosures?

Motor enclosures refer to the type of protective casing that surrounds an electric motor. This is what protects the important components from debris, or inclement weather.

When selecting an electric motor for an application, one important consideration is the motor’s enclosure type. The National Electrical Manufacturers Association (NEMA) has standardized enclosure types to classify the various constructions and protective housings used on motors.

Knowing the differences between NEMA motor enclosure types will help you choose a motor suitable for its operating environment. This overview covers the common NEMA motor enclosure designs:

Open Motors

Open motors, as the name implies, have no housing or protective cover. Open (O) enclosures have no housing and the motor will have exposed components. They provide no protection, which allows for maximum ventilation.

The interior components are fully exposed. This design provides no protection from contact or debris, but allows for maximum ventilation and heat dissipation.

Open construction is very uncommon, limited only to specialized applications.

Enclosed Motors

Enclosed motors have a protective housing surrounding the stator and rotor. The housing blocks direct contact and helps keep dirt and debris out of the internal motor components.

GE motor

Enclosures may include fan cowlings, screens, and sealed covers for further protection. Common enclosed motor types include:

  • Totally enclosed (TE): Surrounds internal parts to prevent entrance of dust, contact, moisture.
  • TEFC: Totally enclosed, fan-cooled motors use shrouds and fans for forced airflow cooling.
  • TEAO: Totally enclosed air-over motors rely on the movement of external air for cooling.
  • TEWAC: Totally enclosed water-air-cooled motors use heat exchangers to allow both air and liquid cooling.
  • Drip-proof (DP): Prevents falling drops of liquid from entering. Allows airflow for ventilation.
  • Weather protected (WP): Additional protection from ingress of rain, snow, splashing water.

What is a TEFC Motor?

TEFC stands for “totally enclosed, fan cooled” and is a type of electric motor enclosure. TEFC motors are completely surrounded by a housing that seals internal components from outside elements and contaminants.

Cooling fans mounted on the external housing circulate air through the enclosure to remove heat from the inside of the motor.

What is a TEAO Motor?

TEAO stands for “totally enclosed air over” and is a type of electric motor enclosure. TEAO motors are fully surrounded by sealed housings that rely on the passage of external air for cooling.

The housing blocks dirt and moisture but has ventilation openings that allow outside air to flow over the frame and cool the enclosed motor.

What is a TEWAC Motor?

TEWAC stands for “totally enclosed water-air cooled” and is a type of electric motor enclosure. TEWAC motors use heat exchangers that allow both air and liquid to pass through the sealed housing to cool the motor.

This dual cooling method makes TEWAC motors suitable for very high temperature environments that require additional cooling beyond standard air circulation.

What is a Weather Protected (WP) Motor?

WP stands for weather protected. This is an enclosure which protects the motor from the (you guessed it) weather conditions. There are two types of weather protected motors: WP1 and WP2.

WP1 motors have an enclosure that provides protection from drops of liquid or light splashing. These “weather protected type 1” motors can handle occasionally moist or wet environments but not continuous exposure.

WP2 motors feature an enclosure that goes beyond WP1 and gives additional sealing against rainfall, snow, and windblown dust. These weather protected type 2 motors can withstand wetter outdoor environments with moderate moisture and precipitation.

Hazardous Location Motors

Where potentially explosive vapors or combustible dusts are present, special hazardous location motors must be used. These motors are carefully designed and constructed to contain sparks and prevent ignition. Common hazardous location motor types include:

  • Explosion-proof: Designed to contain internal ignition while operating normally.
  • Dust-ignition-proof: Prevent ignition of exterior dust layers on the motor.
  • Non-sparking: Use specialized windings and electronics to avoid sparks.
  • Waterproof – Protects from submersion or high pressure water spray.

The particular hazardous environment and associated electrical codes determine which construction is required.

What is the Purpose of an Enclosure?

A motor enclosure refers to the housing, cover, or protective casing surrounding the core components of an electric motor. The main purposes of a motor enclosure are:

  • Protect internal parts – Keep dirt, debris, moisture, and other contaminants away from the motor windings, rotor, and electrical connections. Prevents damage to core components.
  • Prevent contact – The enclosure provides a barrier so external objects and fingers/appendages cannot contact dangerous moving or electrically live parts. Improves safety.
  • Contain noise/vibrations – Enclosures help dampen the operational noise and vibration levels of an electric motor.
  • Facilitate cooling – Many enclosures include dedicated air circulation paths, fans, ventilation openings, or heat exchangers to help remove heat from the motor.
  • House accessories – Enclosures provide space for additional components like control boards, sensors, terminal boxes, cooling fans and conduit connections.
  • Protect environment – A sealed enclosure prevents oil leaks and traps any potential sparks, explosive gases, or dangerous particles emanating from the motor.
  • Mounting – The enclosure often includes brackets, feet, flanges or other means to facilitate securing the motor to floors, walls or machinery.

Summary – Different NEMA Enclosures For Motors

Understanding the strengths and limitations of different NEMA enclosures allows matching the appropriate motor design to the expected operating conditions. Consider ventilation requirements, expected contaminants, hazardous gas or dust risks, and moisture exposure when selecting a motor enclosure type.

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