Technicalworld

Instrument transformer

Instrument transformers are high accuracy class electrical devices used to isolate or transform voltage or current levels. The instrument transformer are also used for measurements of power factor, frequency and for indication of synchronism.

Current transformer

Current transformers are used so that ammeters and the current coils of other instruments and relays need not be connected directly to high-current lines. In other words, these instruments and relays are insulated from high currents. Current transformers also step down the current to a known ratio. The use of current transformers means that relatively small and accurate instruments, relays, and control devices of standardized design can be used in circuits.

Current transformer

Potential transformer

The potential transformer operates on the same principle as a power or distribution
transformer.
The main difference is that the capacity of a potential transformer is small compared to that of power transformers. Potential transformers have ratings from 100 to 500 volt-amperes (VA). The low-voltage side is usually wound for 115 volts or 120 volts.
The load on the low-voltage side usually consists of the potential coils of various instruments, but may also include the potential coils of relays and other control equipment. In general, the load is relatively light.