16–71 Phase Converter Efficiency Three-phase motors are often used in equipment because they are more efficient and reliable than single-phase motors.

Such equipment may be installed in locations where only single-

phase power is available and the cost of installing threephase service is prohibitive. The rotary phase converter in Figure P16–71 is one way of providing three-phase power from a single-phase source. Simply stated, the converter is a rotating transformer that shifts the phase of a portion of the single-phase input to produce a balanced set of threephase voltages. In a certain application, a converter supplies three-phase power to a 30-hp motor ð1 hp = 746WÞ that is 85% efficiency at full load. At full load the single-phase inputs are 220 V ðrmsÞ and 150AðrmsÞ at a power factor of 0:9 lagging. Find the efficiency of the converter.

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FIGURE P16-71 34 OUT