MICROFICHE REFERENCE LIBFUUW - Cd3wd.com

and the usually more common availability of alternating current (Anderson,1973), AC motors are more often utilized. Both types of motors havesingle or three phase varieties of construction? with single phase unitsused primarily for power requirements of less than 10 hp. Particularly 'when used outdoors, waterproof or weatherproff models are also usuallyspecified to protect a motor from natural elements, i.e., dust, rain, ice,insects,etc.The efficiency of motors (i.e .,in converting electrical to mechanicalenergy) increases with size. Table 5.5 gives some typical efficienciesof various hp sizes. Although the price of motors varies with factorssuch as manufacturer, size, construction, (and for used motors, condition),Table 5.5 also lists some typical 1975 prices in the United States.Geographic area will, cf course, also vary price, e.g., in Southeast Asia,a locally manufactured 25 hp motor could be expected to cost closer to$700 (Molenaar, 1956).Table 5.5 Typical electric motor efficiencies and pricesSize(rated hp)l/12l/4l/215102550100 "Price (U.S. 1975 $)*NewUsed30 2065 !!n85 50123 55200 --320 175580 --1,030 2902,800 1,300Eff(%)*Without accessories (e.g., starter); typical prices @ 1800 rpm,higher prices for higher or lower rpm models.