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16 Different Types of Transformers and Their Working [PDF]

In this article, you will learn what is a transformer? And 16 different types of transformers are explained with Pictures. You can also download the PDF file of this article at the end of it.

What is a Transformer?

A transformer is a device used in power transmission to transfer electrical energy from one electrical circuit to another, or in multiple circuits at a time. In other words, it is a voltage control device that is widely used in the distribution and transmission of AC power.

These are made to increase or decrease the AC voltage between the circuits while controlling the frequency of the current by creating a conductive connection between the two circuits.

This is done through the application of Faraday’s law of induction which states that “the magnitude of the induced voltage in a coil is proportional to the rate of change of the magnetic flux which cuts across the coil”.

Transformers can also be used for isolation, where voltage is equal to the voltage output, with the individual coils not electrically tied to each other. A wide range of transformer designs and sizes are located in electronic and electric power applications.

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Types of Transformers

Following are the main types of transformers:

  1. Step down transformer
  2. Step up transformer
  3. Single phase transformer
  4. Three phase transformer
  5. Power transformer
  6. Distribution transformer
  7. Current transformer
  8. Isolation transformer
  9. Potential transformer
  10. Instrument transformer
  11. Air Core transformer
  12. Iron core transformer
  13. Ferrite core transformer
  14. Toroidal core transformer
  15. Autotransformer
  16. Grounding or earthing transformer

#1 Step Down Transformer

Step Down Transformer - Types of Transformers
Image: IndiaMart

A step down transformer converts high voltage from the primary side to low voltage on the secondary coil resulting in a decrease in the output voltage. In this, the overall winding ratio of primary and secondary is always more than 1.

This means that the primary side has more windings as compared to the secondary side. In case a single-phase power outlet voltage is converted to a desired low voltage level, a step-down transformer is required. Generally, step down transformers are used in power distribution systems.

#2 Step Up Transformer

Step Up Transformer - Types of Transformers

These types of transformers work almost the same as step down transformers. A step up transformer can convert low voltage from the primary side of the transformer to high voltage on the secondary side of the transformer.

In this, the ratio of the primary winding to secondary winding is less than 1 because the number of turns on the secondary is always greater than the number of turns on the primary. These devices have no internal moving parts and work on the principle of magnetic induction. A step-up transformer is mainly used in electrical power distribution.

#3 Single Phase Transformer

Single Phase Transformer - Types of Transformers

A single-phase transformer is a type of power transformer that uses single-phase alternating current, which means it relies on a voltage cycle that operates in an integrated time phase. These are basically works based on the principle of Faraday’s law of electromagnetic induction.

At constant variation of frequency and voltage level, the transformer transfers AC power from one circuit to another. It has two types of windings, the primary winding to which the AC supply is given and the secondary winding to which the load is connected. These are used for domestic inverters and for power supply in non-urban areas.

#4 Three Phase Transformer

Three Phase Transformer - Types of Transformers

These transformers are used to convert the voltage of electronic systems with three-phase. They are available in various configurations, such as star-star, delta-delta, star-delta, and delta-star. Three-phase transformers are used to generate electricity and distribute it according to the power usage.

It is a transformer composed of three sets of primary and secondary windings, each set wound around an iron core assembly. Since they have three sets of windings, the primary and secondary windings will be combined to form a complete unit in either a star or delta configuration.

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#5 Power Transformer

Power Transformer

A power transformer is used to convert power from one circuit to another without changing its frequency. They are usually large in size and do not have any rotating or moving parts. The transformer works on the principle of mutual induction and requires an AC supply. Power transformer ratings are as follows 400kv, 200kv, 110kv, 66kv, 33kv.

It changes the voltage for the current in a circuit, while not impacting the total electrical power. So it takes high-voltage electricity with a small current and converts it into low-voltage electricity with a large current. Power transformers are seen in the public electricity grids and are generally used for the purpose of transmission of heavy loads.

#6 Distribution Transformer

The distribution transformer provides the last or final voltage change in the power distribution system. Distribution transformers are like step down transformers, which convert high grid voltage into the voltage required by the end customer.

These transformers have low ratings such as 11 kV, 6.6 kV, 3.3 kV, 440 V, and 230 V. They are small as well as large in size and have a rating of less than 200 MVA. Distribution transformers are typically located at a service drop, where wires run from a utility pole to the customer’s premises.

#7 Measurement or Instrument Transformer

Instrument Transformer

These are high accuracy class devices used to change the voltage or current levels. These transformers are used to measure electrical quantities like current, voltage, power, frequency, and power factor. The instrument transformer has a relay to protect the power system.

In this, the primary winding is connected to the high voltage or current circuit and the relay is connected to the secondary circuit. These are medium in size and are used for 5A current and 100 to 200 V.

#8 Current Transformer

Current Transformer

Current transformers are commonly used to reduce or multiply alternating current (AC). This transformer produces a current in its secondary winding while it is proportional to the current in its primary winding. In addition, they are also used to measure and protect electricity.

When the current is too high and is applied directly to the measuring device, the current transformer helps to convert the high current in the circuit to the required value. Current transformers are current-detecting units of power systems and are used in stations, electrical substations, and industrial production.

#9 Isolation Transformer

Isolation Transformer

This type of transformer is used to transfer electrical power from an alternating current while isolating the powered device for safety reasons. The isolation transformer can provide galvanic isolation which means that no conductive path exists between the source and the load.

They can operate as step-up transformers or step-down transformers and have a turn ratio of 1:1, which means that the primary and secondary voltage is equal. This isolation is used to protect against electric shock and to suppress electrical noise in sensitive equipment. These are used in computers, measuring devices, or power electronic devices.

#10 Potential Transformer

Potential transformers or voltage transformers are commonly used to reduce voltage levels. They cannot be used to supply natural power to a load and are used with voltmeters, wattmeters, frequency meters, circuit breakers tripping circuits, etc.

In this, the primary winding is connected to the high voltage circuit and the secondary winding is connected to equipment or other circuits.

#11 Air Core Transformer

In this transformer, both the primary and secondary windings are set on a non-magnetic stripe. It has flux linkage in both the windings through the air. The mutual inductance in the air-core is low, which means the reluctance to be given to the generated flux is high in the air medium.

Smaller electronic devices use air core transformers which are based on antenna coils. They are common among communication devices because they lack a core, which makes them ideal for portable devices. These are normally located in radio transmission systems.

#12 Iron Core Transformer

Iron Core Transformer

In this type, both the primary and secondary windings are set on multiple soft iron plates providing an ideal connection to the flux. Compared to the air core, it offers less reluctance to linkage flux due to the conductive and magnetic properties of iron.

Since they have a high magnetic permeability capability, they are used to limit and direct magnetic devices such as electric motors, generators, inductors, etc. Different types of core plates are available in the market depending on the core size and shape. These are the widely used types as well as they are heavy in weight and size.

#13 Ferrite Core Transformer

Ferrite Core Transformer

This type of transformer uses a magnetic core made of ferrite on which the windings of power transformers and other parts are made. Ferrite cores have high magnetic permeability, so they are used in high-frequency applications such as switch-mode power supplies.

The reason is that it provides low losses at high frequencies, so they are used extensively in the cores of RF transformers. Ferrite core transformers are also available in a variety of sizes, shapes depending on the requirement of the application.

#14 Toroidal Core Transformer

Toroidal Core Transformer

The toroidal core transformer uses a magnetic core which almost looks like a ring or donut called a toroidal. They are passive electronic components, consisting of a circular ring-shaped magnetic core of ferromagnetic material around which the wire is wound.

Due to their built-in design, leakage inductance is very low and provides very high inductance. This transformer is used in a wide range of electronic circuits such as power supplies, inverters, and amplifiers.

#15 Autotransformer

These types of transformers use a common winding for both primary and secondary windings. The autotransformer winding has three taps where the electrical connections are made. Autotransformers have the advantage of being smaller, lighter, and cheaper than typical transformers.

But it also has the disadvantage that it cannot provide electrical isolation between the primary and secondary circuits. In addition, they offer lower leakage response, lower losses, lower excitation current, and increased VA ratings for a given size and mass.

#16 Grounding or Earthing Transformer

Earthing Transformer
Image: Wikipedia

It is an underground WYE or delta-connected system used to provide a ground path or neutral in a three-phase electric power system. This can help reduce the voltage transients when a ground fault happens.

These are part of an earthing system of a network, in that they allow a three-phase system to adjust phase-to-neutral loads by providing a return path for current to neutral. The grounding transformer usually includes a single winding transformer with a zigzag winding design.

Wrapping It Up

Types of Transformer

As we discussed already, a transformer is a massive component that transfers electric power from one circuit to another. The above types of transformers are not limited as they are of many types available and they are not related to this article.


So for now, I hope I’ve covered everything about “types of transformers“. If you still have any doubts or questions on this topic, you can contact us or ask in the comments. If you like this article then please share it with your friends.

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About Yousef

He is a mechanical engineering student, he likes to write about engineering stuff and he is really interested in learning about new technology in machines.

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