THREE-PHASE CIRCUITS Basic AC PowerFigure 10 Three-Phase ACThree-phase equipment (motors, transformers, etc.) weighs less than single-phase equipment ofthe same power rating. They have a wide range of voltages and can be used for single-phaseloads. Three-phase equipment is smaller in size, weighs less, and is more efficient thansingle-phase equipment.Three-phase systems can be connected in two different ways. If the three common ends of eachphase are connected at a common point and the other three ends are connected to a 3f line, itis called a wye, or Y-, connection (Figure 11). If the three phases are connected in series to forma closed loop, it is called a delta, or D-, connection.ES-09 Page 18 Rev. 0
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