Three-Phase Circuits

Three-phase alternating current voltage is generated in the power station by using the three-phase AC generator and turbine. Three-phase circuits are most common for generating, transmitting and distributing electric power. Over single-phase circuits, three-phase circuits or systems have many advantages such as better voltage regulation, requiring only three-fourths of the weight of the copper to transmit the same amount of power over a fixed distance at a given voltage, more economical for transmitting power at a constant power loss. Three-phase machines are smaller, simpler in construction and have better operating characteristics. Three-phase AC voltages are phase-shifted from one another by 120 degrees. This chapter discusses three-phase voltage generation, voltage and current relationship, and different types of power for wye-connection and delta-connection.