What are the types of Electrical Transformers and their Types?

A transformer is a stationary or static electrical machine that transforms electrical power from one circuit to another and still maintains a static frequency, this is called mutual induction because transformers don’t have moving parts like other mechanical devices.

Types of Transformers

There are different types of transformers based on their use and how they are constructed, which are:

  • Three Phase and Single Phase Transformers – Three Phase Transformer is more cost-effective to transform electricity than a Single Phase, and they are generally used in three-phase power systems. It is preferable to use Three Single Phase Transformers to transform electricity than to use a single Three Phase Transformer.


  • Step Up and Step down Transformers – As the name implies, these transformers are generally used for stepping up and stepping down the voltage level in the transmission and distribution network.


  • Two Winding and Auto Transformers – Two Winding Transformers are generally used where the ratio between high voltage and low voltage is greater than 2. It is cost-effective to use Auto Transformers where the ratio between high voltage and low voltage is less than 2.

Two Winding transformers are used to maintain the voltage ratio when is greater than 2 between high and low voltage. While Auto Transformer is cost-effective to be used where the voltage ratio between the high and low voltage is less than 2.

  • Power Transformers, Distribution Transformers & Instrument Transformers – Power transformers are generally used in the transmission network for stepping up or down the voltage level. It operates mainly during high or peak loads and has maximum efficiency at or near full load.

Distribution transformers step down the voltage for distribution purposes to industrial, commercial, institutional, and residential facilities. It has good voltage regulation and operates 24 hrs a day with maximum efficiency at 50% of full load.

Instrument transformers including Current Transformers and Potential Transformers are used to reduce high voltages and current to lesser values that can be measured by conventional instruments.

  • Core type, Shell Type & Berry Type Transformers – Core type transformers have two vertical legs or limbs with two horizontal sections named yokes. Core type transformers are rectangular in shape with a common magnetic circuit. Cylindrical coils (HV & LV) are placed on both limbs.

Shell-type transformers have a central limb and two outer limbs. Both HV and LV coils are placed on the central limb. A double magnetic circuit is present.

In Berry type transformers, the core looks like the spokes of a wheel. Tightly fitted metal sheet tanks are used for housing this type of transformer with transformer oil filled inside.

  • Oil Cooled & Dry Type Transformers – In oil cooled transformers, the cooling medium is synthetic transformer oil whereas dry-type transformers are air-cooled.

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