8: Potential Transformers

 Potential Transformers

Potential transformers (figure) are used with voltmeters, wattmeters, watt-hour meters, power-factor meters, frequency meters,

synchroscopes and synchronizing apparatus, protective and regulating relays, and undervoltage and overvoltage trip coils of circuit breakers.

One potential transformer can be used for a number of instruments if the total current required by the instruments connected to the secondary winding does not exceed the transformer rating.

Potential transformers are usually rated 50 to 200 volt-amperes at 120 secondary volts. 

The secondary terminals should never be short

circuited because a heavy current will result, which can damage the

windings.