Transformers and Coupled Circuits

Abstract

An important feature of a.c. distribution systems is the ease with which the system voltage can either be increased or reduced by means of transformers. When transmitting a given amount of power, a high supply voltage results in a small line current with consequent small copper losses (I²R losses). Thus, when large amounts of power are transmitted over great distances, it is done at a very high voltage, typically several hundred kilovolts. In local distribution networks the line voltage may be 11 or 6.6 kV, and in medium and large sizes of industrial installations power is distributed at 3.3 kV. The voltage at which the supply is utilised depends on the nature of the installation, and may be at a line voltage of 3.3 kV in the case of large machines or 415 V in smaller machines. Intermediate voltages such as 1.1 kV are used in some industries.