Electrical Transformer Types, Parts, Diagram, Applications

A transformer is an electrical machine that transfers electrical energy from one circuit to another circuit without any metallic or conductive path. Transformer works on the principle of faraday's laws of electromagnetic induction. Generally, a transformer has two separate inductive coils wound on the same core. When any one of these coils is connected to the alternating or varying power supply, a varying magnetic field is produced in that coil. This varying magnetic field causes to create a varying electromotive force in another coil wound on the same core. And, if that coil is connected to a closed-circuit electrical current will start to flow.

The coil which connected to the power supply is called the primary coil and the coil which connected to the load is called the secondary coil. Transformers transfer the electrical energy by varying the voltage and current and keeping constant the power and frequency. A step-up transformer increases voltage but decreases the current whereas a step-down transformer decrease voltage but increases current.

Electrical Transformer Parts

The main parts of the transformer are,
  1. Primary Coil
  2. Secondary Coil
  3. Core

main parts of transformer, transformer parts, electrical transformer

These parts are essential for the working of a transformer. And all of the transformers have these basic three parts. But, if we see the physical construction of the transformer then the following parts also be added,
  1. Terminals and Bushings
  2. Conservator Tank
  3. Normal oil tank
  4. Breather
  5. Explosion Vent
  6. Radiator and Fan
  7. Buchholz Relay
  8. Tap Changer
  9. Insulators and Insulation
  10. Transformer Oil

Primary Winding or Primary Coil of Transformer

The coil or winding of a transformer that is to be connected to the input power supply is called Primary Winding. In a step-down transformer, the primary winding has more turns than secondary winding but thickness is less than secondary winding. In a step-up transformer, the primary winding has fewer turns than secondary winding but thickness is more than secondary winding.

Secondary Winding or Secondary Coil of Transformer

The winding of a transformer that is to be connected to the load is called secondary winding. In a step-down transformer, the secondary winding has fewer turns than the primary winding but has more thickness. On the other hand, is a step-up transformer, the secondary winding has more turns than primary winding but has less thickness.

Transformer Core

The transformer core is that on which both the primary and secondary winding of a transformer is wounded. The main function of the transformer is to conduct the magnetic flux from the primary winding to the secondary winding. The property of a transformer core is low reluctance and high resistance. Generally, all the transformer cores are made with lamination to eliminate the eddy current loss.

Transformer Tank

The transformer tank is space for placing all the windings and core. So, both of the primary and secondary winding are placed in the transformer main tank wounding on the transformer core. In fact, the overall size of the transformer depends upon the transformer tank.

Transformer Oil

The main tank of the transformer is filled with oil, and that is called transformer coil. So the windings of a transformer are immersed in the transformer oil. The main function of the transformer oil is to provide insulation between coils and absorbed heat produce by the winding. Generally, hydrocarbon mineral oil is used as transformer oil.

Conservator Tank

The transformer conservator tank provides an adequate space when transformer oil expands due to absorbing more heat. So when the transformer oil absorbs more heat it expands and excess oil moves from the main tank to the conservator tank.

Explosion Vent

It is placed above the conservator tank. The explosion vent is constructed with a diaphragm. The main function of the explosion vent is to remove the oil and gases from the transformer in emergency cases. Due to any internal fault, when oil expands more and high pressure is created inside the transformer, the diaphragm helps to exit the oil and gas to maintain the pressure inside the transformer.

Buchholz Relay

Buchholz relay is connected between the main tank and conservator tank. It is operated with gas and oil. When due to any internal fault the transformer oil expands and gas is produced, they start to go towards the conservator tank. At this time the Buchholz relay senses the fault and disconnects the transformer from the main incoming power supply.


Breathes helps to keep the transformer oil free from moisture. Due to temperature variations, the oil expands, transformer takes air from outside to inside. So the air enters inside the transformer through the breather. So entering time, the breather removes the moisture from the air.

Terminals and Bushing

The bushing is the arrangement to connect the incoming and outgoing lines to the transformer terminals safely. The main function of the bushings is to provide insulation between the live current-carrying conducting terminals and other parts such as the transformer's metallic body.

Insulator and Insulation

The bushing is one type of insulator. Transformer coils are also insulated by paper insulation. The transformer's metallic body was also painted for insulation purposes.

Tap Changer

Tap Changer is the arrangement to change the output voltage level of the transformer. It is basically connection to the winding by maintaining a certain number of turns. Generally, the tap changing is provided on the high voltage side of the transformer. There are so many advantages of using tap changing on the high voltage side such as,
  1. High voltage side of the transformer carrying low current so there are very few chances of sparking during the operation of tap changing.
  2. In most of the transformer high voltage winding places at the outer side so it is very helpful for brought out the tappings.
  3. Providing tap changing on the high voltage side make the transformer operates with lower voltage at the average time.

Electrical Transformer Types

There are three types of Transformer based on the voltage level,

  1. Step Up Transformer - Secondary voltage higher than the primary voltage
  2. Step Down Transformer - Secondary voltage lower than the primary voltage
  3. Isolation Transformer - both primary and secondary voltage are the same

types of transformer, electrical transformer types

Based on the Core material, a transformer is classified into four types,

  1. Iron Core Transformer
  2. Ferrite Core Transformer
  3. Toroidal Core Transformer
  4. Air-Core Transformer

Based on the winding arrangement, there are two types of transformer,

  1. Auto Transformer - Having a single coil or single winding
  2. General Transformer - Having two windings primary and secondary

Based on the applications there are five types of transformer,

  1. Power Transformer
  2. Distribution Transformer
  3. Measurement Transformer
  4. Pulse Transformer
  5. Audio Transformer

Measurement Transformer also has two types,

  1. Current Transformer(CT)
  2. Voltage Transformer or Potential Transformer(PT)

Electrical Transformer Applications

1. You can see the applications of normal step-down transformers in Rectifier Circuits, Battery Charger circuits, old TVs, Amplifiers, etc. Large step down transformers are used for electrical power Distribution purpose at the domestic consumer end.

2. Step Up Transformers are used in stabilizers, industrial control, heavy machinery, etc. Large step up transformers are used in power transmission system to transmit the electrical power with a very high voltage to minimize the power loss.

3. Isolation transformers are used in power electronics circuits, industrial control systems, etc.

4. Current and voltage transformers are used in measuring instruments, electrical control panels, automation systems, etc.

5. Audio transformers are used in amplifier circuits, equalizing circuits, etc.

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Electrical Transformer Types, Parts, Diagram, Applications Electrical Transformer Types, Parts, Diagram, Applications Reviewed by Author on October 19, 2021 Rating: 5
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