Explosion-Resisting Motors

Author: E.E. Kimberly

Totally enclosed motors are not necessarily gas-tight. For operation in atmospheres of petroleum derivatives (gasoline, etc.), lacquer-solvent vapor, etc., specially enclosed motors, known as explosion-resisting motors, are required by the National Board of Fire Underwriters.

Fig 12-2: Totally Enclosed Fan-Cooled Motor

The horsepower rating of a totally enclosed motor may be restored almost to its "open" rating by means of a fan arranged to blow air over the outside of the frame. Another fan inside the motor is used to agitate and circulate the enclosed air to bring the heat from the windings to the cooling surfaces. A totally enclosed fan-cooled motor is shown in the cut-away drawing in Fig. 12-2.

1	For further classification of motors, see Standards of the American Institute of Electrical Engineers, No. 5.