Motor enclosures totally enclosed

Cooling tower fan motors must be properly selected for long life and trouble free operation. In addition, it is important to match the motor s enclosure to the application. Motors in draw through applications that are mounted directly in the air stream, for example, experience tough duty and must be of the totally enclosed type. Motors are categorized as follows ... 

TEAO - Totally Enclosed Air Over where the motor has large cooling fins and depends on the cooling tower air stream for air movement. The motor shaft protrudes from the enclosure at one place only. 

Motor enclosures for outdoor use are NEMA weather-protected Type II, totally enclosed, fan-cooled, or drip-proof with weather protection. Motors of the latter type are widely used. Not only are they less expensive than the other types, but they also have a service factor of 1,15. The above enclosure types are all suitable for the Class I, Group D, Division 2 classifications usually encountered. 

Motor enclosure Open drip proof Totally enclosed. . Explosion proof ... 

Motors shall be squirrel cage induction type with (totally enclosed, fan-cooled) (encapsulated) (splashproof) enclosure and roller-type bearings with NEMA Class A insulation. Motors shall be (single... 

FIG. 29-4 Examples of open dripproof, totally enclosed fan-cooled, and weather-protected motor enclosures. Photo courtesy of Reliance Electric Company, Cleveland, Ohio.)... 

Fire or explosion hazards require special motor enclosures. Hazards include combustible gases and vapors such as gasoline dust such as coal, flour, or metals that can e3q)lode when suspended in air and fibers such as textile lint. The kind of motor enclosure used depends on the type of hazard, the type and size of motor, and the probability of a hazardous condition occurring. Some available enclosures are explosionproof motors, which can withstand an internal ejq)losion force-ventilated motors cooled with air from a safe location and totally enclosed motors cooled by air-to-water heat exchangers and pressurized with safe air, instrument air, or inert gas. 

Electric motors select synchronous for low speed usual application for either synchronous or induction 500 to 2100 rpm 150 to 500 kW. Usually use total enclosed Fan cooled (TEFC) enclosure, efficiency 84 to 95%. 

The efficiency is set by the pump manufacturer when the final pump selection is made. It is usually based on their shop tests for the same model and size pumps. The pump efficiency can vary between 10% and 80%. Pump electric motor specifications require mechanical and electrical requirements. Motors can vary in size depending upon power, speed (RPM), frame size, area classification, orientation, service factor and type of enclosure (e.g. totally enclosed fan closure). 

B. Totally enclosed fan-cooled (TEFC) The motor is cooled by a fan integrally mounted to the enclosure blowing cooling air over the endosure. 

The drip-proof, general-purpose motor is suitable for dry, clean, and ventilated locations. Wet, dirty, or explosive conditions require other enclosures, such as totally enclosed fan-cooled or totally enclosed nonventilated motors in standard, severe duty, or explosion-proof construction. Table 5.33 matches enclosure to environment. 

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