Current Transformer

Current transformer is a system used to convert the current of the circuit to which it is connected. Through this system, it is possible to measure and control the electric current at large values. The current transformer consists of two windings, primary and secondary.

Current transformer is one of the tools used to measure, control and safely use electric current. Its working principle is based on the principle of electromagnetic induction. The magnetic field generated by the current passing through the primary winding creates a current in the secondary winding. This current is proportional to the current flowing through the primary winding and usually has a lower value.

What is a Current Transformer?

A current transformer or “transformer” is basically a converter that allows high currents to be measured and controlled. It is preferred because direct measurement in electrical circuits exceeds the capacity and is dangerous in some cases. What is a current transformer used for? Transformers come into play in such cases and convert the high current into a lower current that measuring instruments can read. Thanks to this converter, it is safe and easy to make measurements in the electrical circuit.

Current transformers ratings and other specifications may vary depending on the purpose of the application and the requirements that arise. These values and some of their features can be listed as follows;

Nominal Current (In)

It is the current value that the current transformer can carry continuously. It is usually specified in two different values as primary and secondary.

Short Circuit Current

It is the maximum current value that the current transformer can carry for a certain period of time (usually a few seconds) and at a certain temperature.

Maximum Output

It is the maximum power that the current transformer can deliver from the secondary side and is specified in VA (volt-ampere). For example; 10VA.

Core Material

It contains information about the material from which the core of the transformer is made. Ferrite, silicon, etc. materials are frequently used.

In addition, units such as insulation level, frequency, accuracy class are among the transformer values.

What are the Types of Transformers?

In addition to the question of what current transformers are, the types and features of these transformers are among the frequently searched questions. There are different types that differ in terms of the area of use and the way the product works. Which type to choose depends on the needs of the application and the existing conditions. When choosing a transformer, it is important to consider the requirements and application conditions and to choose the most suitable type accordingly. Among the transformer types, the following stand out;

Split Core Transformers (Split AT)

  • Such ATs can be installed directly without breaking the circuit.
  • They are generally used for retrofitting into existing systems.

Bar Type Transformers (Non-Dismantling AT)

  • Generally used in new installations and at high current values.
  • They can measure with higher accuracy.

Window (or Ring) Type Transformers

  • These transformers pass through the cable or conductor.
  • They are generally used at lower current values.

Protection Current Transformers

  • It is used to trigger protection relays during overcurrent, short circuit, etc.
  • The accuracy class is specially designed for protection (e.g. 5P20).

Measurement Current Transformers

  • Used for measurement and billing purposes.
  • It has a high accuracy class (e.g. 0.5S).

How to Connect Transformers?

The connection process of these transformers requires very careful and meticulous work. Transformers that are not connected correctly can cause both incorrect measurements and various hazards. For this process, it is necessary to work with a current transformer connection diagram and, if possible, with experienced and professional people in the field.

The other steps of this process, which will ensure accurate measurement of high currents, are as follows;

  • Choosing the right transformer,
  • Primary and secondary connection,
  • Grounding,
  • Control,

The nominal current value of the transformer to be selected must be compatible with the maximum current to be measured. The relevant circuits must not remain open during primary and secondary connection. However, completely disconnecting the power supply before the process is the most important step of the process. The protection of the device and the prevention of any danger to persons depends on the care and attention at this stage.

Akım Trafosu