Discussing What A Current Transformer Is, How It Works And How To Apply It

Current Transformer Types and Applications : The Talema Group


The current Transformer is an electrical device that is definitely employed to transfer electric power from one particular circuit to a further with out changing its frequency and achieves it by electromagnetic induction. Transformers are readily available in two types namely shell type and core form.

Its main function is to increase and decrease the voltage. For measurement purposes, instrument transformers are used because these transformers measure current, voltage, and energy meters. It is used in different instruments with conjunctions like voltmeter, ammeter, wattmeter & energy meter. 

Current Transformer Have Various Types, You can Click The Previous Link To Find Out More About The Types Of Current Transformer.

What is a Current Transformer?

Current transformer is a type of transformer that is used to determine the magnitude of the electric current at high voltages. The inside of the current transformer is composed of the primary and secondary windings. The number of primary windings is very small, while the number of secondary windings is very large. The secondary winding is connected to an electrical measuring instrument, namely an ammeter. The secondary section is also connected to the control circuit and protection relay.

How Current Transformers Work

Current Transformer operation is slightly different when compared to standard voltage transformers. Similar to a voltage transformer, it includes two windings.

Whenever AC distributes the entire primary winding, then an alternating magnetic flux can be generated, then AC will be induced in the secondary winding. In this sort, the load impedance is extremely tiny.

Thus, this Current Transformer works in short circuit conditions. So the current in the secondary winding depends on the current in the primary winding but does not depend on the load impedance.

How To Apply Current Transformer

The construction of this Current Transformer includes various features by design such as primary, core, winding, and insulation amperage-turning.

Primary Ampere

The primary amperage turns in a transformer range from 5000 to 10,000 so this is disconnected through the primary current.


To achieve low amperage magnetization rotation, the core material must include low iron loss and low aversion. Core materials such as nickel and iron alloys cover a wide range of properties such as low loss, high permeability.


The leakage reactance within a Current Transformer is usually reduced by placing the windings close to each and every other. The wires used in the primary winding are copper strips and for the secondary wires, SWG is used. The design of these spools can be done for proper strength & fixed bracing without harm.


The transformer windings are insulated making use of varnish & tape. High voltage applications require setting up the insulation which is absorbed by the oil used for the winding.

The core design of the transformer can be done using silicon steel laminates. The main winding of the transformer carries current & is connected to the main circuit. The present inside the secondary winding is proportional towards the current inside the main winding & is connected to a meter or instrument.

The primary and secondary windings are isolated from the core. The primary winding includes a single turn carrying the full load current whereas the secondary winding includes several turns.

The ratio of the currents in the primary and secondary is called the current transformer ratio. Usually, the transformer current ratio is high. The present ratings inside the secondary are 0.1A, 1A & 5A while the current ratings within the main range from 10A – 3000A.