current transformer reviews, specifications, price, measurement, construction, and general overview on current transformer

Complete Review On Current Transformer You Should Know

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The current transformer is either use to increase or decrease the voltage of electricity, in the electrical world, an apparatus called the transformer is needed and this device has many types and one of is the current transformer.

The article is here to furnish you with all the pieces of information you may need to know about the current transformer and its attributes. All the information you need to know is provided below for a better understanding of how the current transformer works.

What Is A Current Transformer?

The current transformer can be described as a type of transformer that helps in decreasing or multiplying the alternating current that is flowing in the electrical field.

This transformer creates a current in its secondary winding that is proportionate to the current in its primary winding.

Current transformer can also be seen as instrument transformers since they work with voltage or potential transformers


To know how to measure a current transformer, the current transformer can be measured from its high voltage subsystem or where a high amount of current is flowing through.

When once the high amount of current is converted to a lower amount of current then it can easily be measured with a user of an analog meter or a microcontroller.

Types Of Current Transformer

There are basically three (3) types of current transformers. They are as follows:

Wound Current Transformer: In this type of current transformer, primary winding is connected physically in series with the conductor which is carrying the measured current flowing in the circuit.

Toroidal Current Transformer: This type of current transformer doesn’t have a primary winding, therefore, the current that flows in the network is via a window or hole in it.

Bar Type Of Current Transformer: This type of current transformer makes use of actual bus-bar or cable of the main circuit as the primary winding.

Current Transformer Construction

The construction of current transformers is based on its design but it will need materials like the core, windings, ampere-turns and insulation.

The amount of primary ampere turns to be used can be between 5000 to 10000, the core material to be used should have low iron losses and low reluctance like the alloy of iron or nickel.

The leakage reactance in this transformer needs to be decreased via placing the windings close to each other. Then for insulation, the windings of the transformer need to be insulated with the use of tape and vanish.

To design this transformer the core which is in the transformer need to be done using a silicon steel lamination. Then the primary and secondary windings need also to be insulated from the cores.

Current Transformer Specifications

A typical current transformer has the following specifications (spces):

  • Multio ratio: different ratio per outputs
  • Three phase: used for three phase system
  • Split core in use
  • Toroidal/window
  • Bar in use
  • Has pc mount
  • Waterproofed
  • Military standard
  • Meet ANSI C12 standards
  • IEC 1036 standards

The Rating Factor

The current transformer rating factor is all about the indication of current transformer’s overload capability.

This rating shows the amount, the primary load and current that may have rise over its rating without going or passing the allowable temperature rise.

So to make a lot of sense, the ambient temperature that the rating factor applies is outlined. Normally the ambient reference levels should be between 30 Celsius to 55 Celsius.

Current Transformer Price

The price of a current transformer varies according to brand name, SKU, and even its current ratio but if you need to get one, then you should budget between $40 and $100 to get a good one.


What is current transformer used for? Current transformer which is a device is solely used for the production of alternating current in its secondary, this current is also proportional to the AC current that is created in its primary.

So when a voltage or current is too high to measure directly, the best transformer to use for such measurement will be the current transformer.


Current transformer testing is carried out during the development, creation, installation and maintenance of CT. this testing can be carried out in several ways. The CT testing consists of the following tests:

  • Excitation Test: This test is about injecting a specific voltage on a secondary side then the primary side is only been read.
  • Polarity Test:  This test is to ascertain that the direction of the secondary current is right
  • Ratio Test: This is a test to compare the ratio of the primary current to the secondary current
  • Winding Resistance Test: This is about dividing the voltage drop across the winding by the DC current readings via the windings
  • Insulation Resistance Test: This test is to know whether the resistance reading is still constant
  • The burden Test: This is used to read the signal on the secondary side after an application of high current to the primary side.

Current Transformer In Substation

The current transformer which is a step up transformer can be used for protection purposes as well as for measurement in substation.

Application Of Current Transformer

The current transformer can be applied or used for different purposes: it can be used for the protection of high voltage.

It is also for the measurement and control of high voltage electrical grid and its substations. Current transformer can be installed inside an apparatus bushings or the switchgear though mostly it will be the free-standing outdoor transformer that would be used.

It is also applicable for measurement of currents high magnitude. It also a good application for the step down of current to be measured which will enable the measurement of it with ammeter to get the normal range.


The connection of the current transformer which is through the primary winding is in series with the transmission line whose current needs to be measured. The core of this current transformer is created with the lamination of the stainless steel.


So the current transformer is a valuable device that is specifically created to measure current and its flows. You have other details above and with this, you would have gotten the needed knowledge you need to know about the current transformer.

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