What is a Totally Enclosed Fan-Cooled (TEFC) motor?

• A. A totally enclosed fan cooled motor is completely air-tight and keeps moisture out entirely
• B. A TEFC motor prevents free exchange of air between inside and outside the enclosure and uses a fan to blow air over the outside of the enclosure to aid cooling
• C. A TEFC motor relies on oil cooling
• D. A TEFC motor is identical to an Open Drip Proof motor

Answer: (B)

The main idea here is how a TEFC motor manages cooling while keeping the enclosure sealed. TEFC means Totally Enclosed Fan-Cooled: the enclosure prevents air from freely entering or leaving the inside, keeping out dust and moisture. Cooling is achieved by a fan that moves ambient air across the outside of the motor housing, carrying heat away from the fins on the exterior. The windings stay inside a sealed enclosure, and heat is removed by air flowing over the outside of the housing rather than through the windings.

So, the best description is that the motor prevents free air exchange between inside and outside the enclosure and uses a fan to blow air over the outside of the enclosure to aid cooling. It isn’t completely airtight, it doesn’t rely on oil cooling, and it isn’t the same as an Open Drip Proof motor.