An instrument transformer operates on the same principle as a power transformer, but it is specifically designed to connect electrical measuring instruments and extend the range of ammeters or voltmeters. The primary winding of this type of transformer is connected to the current or voltage being measured, while the measuring instrument is connected to the secondary winding circuit. Thus, a small current or voltage measured by the instrument is directly proportional to the actual current or voltage to be measured.
The advantages of using an instrument transformer are as follows:
The secondary winding of an instrument transformer provides a lower voltage, which reduces the insulation requirements for the measuring instruments and makes measurement operations safer.
An instrument transformer can isolate the power supply line from the measuring instrument.
Measuring instruments can be run from the instrument transformer to other locations using wires, enabling remote measurements.
The secondary voltage or current of the transformer can be standardized (typically 110V or 5A) to facilitate the interchangeability of measuring instruments.