A current transformer (CT) is a type of transformer that is used to measure AC current. It produces an alternating current (AC) in its secondary which is proportional to the AC current in its primary. Current transformers, along with voltage or potential transformers are Instrument transformer. In this article we will discuss the following topics. 1. Current Transformer Symbol / Circuit Diagram 2. Working Principle of CT 3. Construction of Current Transformer 4. Wound Type, Torroidal and Bar Type Current Transformer 5. Uses / Advantages of Current Transformer