Electric motors enclosures

Using other criteria, compressors are classified as open, semiher-metic accessible), or hermetic. Open type is characterized by shaft extension out of compressor where it is coupled to the driving motor. When the electric motor is in the same housing with the compressor mechanism, it could be either hermetic or accessible (semihermetic). Hermetic compressors have welded enclosures, not designed to be repaired, and are generally manufac tured for smaller capacities (sel-... 

Figure 8 18. Compressor driven by an electric motor through a speed increasing gear. The motor enclosure is a WP2. (Courtesy ofA-C Compressor Corporation)...

After an area classification has been established, then anelectrical equipment, instruments, and wiring must adhere to that classification. Therefore, some motor enclosure types would not be electrically acceptable for specific area classifications. 

Energy Efficient (EE) Motor Designs, 628 NEMA Design Classifications, 630 Classification According to Size, 630 Hazard Classifications Fire and Explosion, 631 Electrical Classification for Safety in Plant Layout, 647 Motor Enclosures, 649 ... 

Electric motors 90-110 Acoustically lined fan covers, enclosures, and motor mutes. 

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

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 f.o.b. purchase cost of an electric motor depends on its power consumption, Pq, the rotation rate of its shaft, and the type of motor enclosure. Cost data are given here for two common motor speeds (3,600 rpm and 1,800 rpm) and three common types of motor enclosures ... 

From the electric motor cost correlations of Corripio et al. (1982a), indexed to mid-2000 (CE = 394), the f.o.b. purchase cost of an electric motor operating at 3,600 rpm, with an open, drip-proof enclosure (referred to here as the base cost, Cg), is plotted in Figure 16.4 as a function of the horsepower consumption, The cost curve is given by the equation ... 

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). 

Electric motors Motors with low speeds are preferable. Big motors to be water-cooled rather than air-cooled. Direct drive by four-pole or variable-speed motors. Choose motor types with low noise emission. Fan blading to have irregular pitch. If necessary, motor enclosure to be provided with special silenced ventilation. Internal combustion engines (e.g., for driving quarry machinery) Exhaust noise can be reduced by using amply dimensioned absorption and reflection silencers. Enclosure of the engine with ventilation system equipped with inlet and outlet silencers and ducts lined with sound-absorbing material (see Funke, 1977). 

Motor enclosures. Table 3-9 lists the various NEMA enclosures for electric motors. 

Ensure that motor enclosures and other electrical equipment are compatible with the electrical hazard rating of the area. 

Table 3-9 lists NEMA s defined types of motor enclosure and describes their main characteristics, and Table 3-10 lists the NEMA enclosures for other electrical equipment. Since sparks from electrical sources are the most common source of ignition of flammable material (Table 2-2), it is important to select the proper NEMA enclosures for motors and electrical contacts. 

Electric-motor application for the plant engineer is the common-sense matching of load requirements with motor characteristics. Motor types, styles, sizes, mountings, and enclosures vary greatly. So the first step in using electric motors correctly is to understand them and the terminology the motor industry uses to describe them. 

Safety Standards (enclosures) for construction and guide for selection, installation and use of rotating machines Sound level prediction for insulated rotating electrical machines Energy management guide for selection and use of three phase motors Polyphase induction motors for power generating stations... 

Oscarson, G. L. and R. L. Kolar, Enclosure Protection for Large A-C Motors, Electric Machinery Co., Div. Dresser-Rand Co. 

---