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Selecting the Correct Motor Enclosure - HECO

May 14, 2019

Are you replacing your failed motor with the best motor for your application and environment? The easy part of replacing your motor is matching the frame size, horsepower, RPM, and voltage, but it may not always be wise to just replace the motor with a motor matching the same enclosure that you have always had.

It is important to consider what enclosure is best for the environment that the motor is going to be installed in. You certainly wouldn’t want to continue on with a mistake that was made when the original motor was selected. Often times equipment OEM’s select a motor based on cost and not what’s in the best interest of the longevity of service.
When considering which motor enclosure is best, look at the type of cooling the motor requires and most importantly the environment that the motor will be operating in.

Open Drip Proof – ODP motors are almost always the least expensive of all motors which often times makes them the preference of equipment OEM’s. These motors operate well indoors in an environment that is free of airborne contaminates.

ODP motors permit the free flow of cooling air. The open design of these motors allow whatever is in the surrounding environment to be pulled through the motor by the internal cooling fans. Not only are the fans pulling dust and dirt through the motor, but any type of humidity in the area around the motor is also pulled in.

The mix of moisture, dust and dirt sticks to the windings plugging cooling vents within the stator laminations causing the motor to operate at temperatures that exceed the insulation limits and shorten the life of your motor.

Totally Enclosed Fan Cooled – TEFC motors, while a bit more expensive than the ODP motor, are usually cheaper considering total cost of ownership. This type of motor is designed for applications where contaminates are factors such as papermills, chemical plants and motors being used outdoors.

TEFC motors provide for exterior cooling, where a fan and fan cover direct air across the outside of the motor and across the cooling fins. A periodic visual inspection of the motor should be considered to ensure that there is no buildup of contaminates on the skin of the motor, which would cause it to operate at a higher than design temperature. With proper maintenance TEFC motors will by far exceed the life of an ODP motor.

These two enclosures described are the most common, but there are several others that can be used for specific environments and applications. The most important thing to remember is that you have options when replacing a motor. Contact a qualified company that has the expertise to assist you in making a selection that is best for you.

Posted in Equipment Management, Predictive

image of a very old electric motor