The Two Main Types of Current Transformers

Current transformers (CT) are generally used to measure and control current in an electrical system. High current levels cannot be fed to a system’s relays and meters, and it’s a CT’s job to quantify our manipulate current to a level that these devices can handle. Based on function, CTs can be classified as follows:

Measuring CTs

This type of CT is typically used in combination with measuring devices for the accurate measurement of energy, current, and power.

Protective CTs

Protective CT types are used in combination with protective devices such as trip coils and relays. Protective CTs can be further classified into three distinct categories, namely: Bar Type, Wound Type, and Window Type.

To differentiate between the three: Bar Type is a CT that consists of a bar and a material that comprises the integral part of the transformer. Wound Type contains a primary winding of ore instead of a full turn wound over the core. Window Type on the other hand, has no primary winding, with the secondary winding placed around the current.

The basic principle behind CTs follows that of the power transformer. Like the latter, all CTs also have primary and secondary winding, with the exception of the Window Type Protective CT.