Voltage Transformation Ratio

Author: E.E. Kimberly

A transformer with an equal number of turns on its primary and secondary windings will have a secondary voltage only slightly less than the primary applied voltage, and its voltage ratio is said to be 1:1. If, however, the secondary winding have only one-half as many turns as the primary winding, the secondary voltage will be only one-half as great as the primary voltage. The voltage ratio then will be 2:1. The primary and secondary generated electromotive forces are proportional to the primary and secondary turns} respectively. Thus,

A transformer with a turns ratio of 13,500 to 110,000 would be used to step up the voltage at the terminals of a 13,500-volt generator to 110,000 volts for long-distance transmission. At the receiving end of the transmission line, another transformer with a turns ratio of 110,000 to 13,500 would be used to step down the voltage to 13,500 volts for local distribution. On the distribution feeders, transformers with turns ratios of 13,500 to 440 or 13,500 to 220 would be used to reduce the distribution voltage to a safe and convenient value for general power application.