ABSTRACT
At the end of this chapter you should be able to:
• describe a single-phase supply • describe a three-phase supply • understand a star connection, and recognize that IL = Ip and VL =
√ 3Vp
• draw a complete phasor diagram for a balanced, star-connected load • understand a delta connection, and recognize that VL =Vp and IL =
√ 3Ip
• draw a phasor diagram for a balanced, delta-connected load • calculate power in three-phase systems using P=√3VL IL cosφ • appreciate how power is measured in a three-phase system, by the one, two and three-wattmeter methods • compare star and delta connections • appreciate the advantages of three-phase systems
Generation, transmission and distribution of electricity via the National Grid system is accomplished by threephase alternating currents.
