What is a current transformer?

What is a current transformer?
A current transformer is an instrument that converts a large current on the primary side into a small current on the secondary side based on the principle of electromagnetic induction. A current transformer consists of a closed iron core and windings. It has fewer turns in the primary winding and is in series on the line where the current needs to be measured.
Therefore, it tends to make all the current of the line flow, and the number of turns of the secondary winding is relatively large. In the case of the measuring instrument and the protection circuit, when the current transformer is working, its secondary circuit is always in a closed state, so the impedance of the series coil of the measuring instrument and the protection circuit is very small, and the working state of the current transformer is close to a short circuit. The current transformer is to convert the large current on the primary side into a small current on the secondary side for measurement, and the secondary side cannot be opened.
Current transformers are divided into the following categories according to the insulating medium:
1. Dry-type current transformer: It is made of ordinary insulating material and treated with varnish as insulation.
2. Casting current transformer: a current transformer cast with epoxy resin or other resin mixed materials.
3. Oil-immersed current transformer: insulating paper and insulating oil are used as insulation, generally outdoor type.
4. Gas-insulated current transformer: The main insulation is composed of gas.