➢ Poly means many (more than one) and phase means windings or circuits, each of them having single alternating voltage of the same magnitude and frequency ➢ Poly Phase system: It is a combination of two or more than two voltages having same magnitude and frequency but displaced from one another by equal electrical angle or phase difference
➢ Poly phase System may be ▪ 2 – phase system ▪ 3 – phase system ▪ 6 – phase system ➢ But all practical purposes, 3 – phase system is employed. Therefore, whenever a poly phase system is mentioned, we mean by that a 3 – phase system unless stated other wise
Introduction • The generator , motor , transformer or rectifier have only one winding is called a single phase system • If the current or voltage follows a phase difference 90 0 in a two windings , called two phase systems • If the phase difference is 120 0 between voltages or currents in a three winding , called as Three phase systems
Advantages of Poly phase system i. Constant Power: In single phase circuits, the power delivered is pulsating, Where as, in poly phase system power delivered is constant when loads are balanced ii. High Rating: The output of 3 – phase machine is nearly 1.5 times the output of single phase machine iii. Power transmission Economics: to transmit the same amount of power over a fixed distance at given voltage, 3 phase system requires 75% of the weight of conducting material of that required by single phase system. iv. Three phase generators not produce the harmonics when they are connected in parallel v. Superiority of 3 – phase induction motors: ▪
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- Winter '18
- Alternating Current, Three-phase electric power, Poly Phase system