Difference Between Autotransformer and Conventional Transformer

What is Autotransformer?

An autotransformer is a transformer in which the same winding serves as both the main and secondary windings. The autotransformer’s windings are electrically and magnetically linked to one another.


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This means that the same winding performs the primary and secondary functions of an autotransformer. As a result, the autotransformer’s windings share a magnetic connection in addition to an electrical one. 

No autotransformer is required to connect the high-voltage and low-voltage systems. It’s put to use whenever a modicum of variety is called for. Contrasted with other transformer types, this one only has one winding. There are two distinct sections in a single winding configuration. There is a primary user and a secondary user.

Step-down autotransformers are used when the voltage in the main winding is higher than the voltage in the secondary winding. A step-up autotransformer is one in which the voltage of the primary winding is lower than that of the secondary.

Autotransformers are famous for their control and affordability. However, their primary winding is not isolated from the secondary winding which can be a major drawback. This means that the load and operator are at risk if the high voltage supplies the low voltage, as the whole voltage will have crossed the secondary terminal.

What is a Conventional Transformer?

A conventional transformer is a stationary apparatus that converts the voltage of an electrical current while keeping the same frequency. The electromotive force is induced in the closed circuit as a result of changes in the surrounding magnetic field, making use of the principle of electromagnetic induction. In a standard transformer, the windings are separated electrically but still magnetically coupled.

A conventional transformer is also commonly known as a two-winding transformer. The primary winding does most of the work. The secondary winding must be linked to the load and be able to receive input from the primary winding to transfer energy from the source to the load. The induction principle used in this transformer is mutual induction.

The two-winding transformer uses magnetic induction to move electricity from one circuit to another. In most cases, the output voltage remains stable. The number of turns in a conventional winding transformer is predetermined. 

Traditional transformers have several drawbacks. It has additional losses and a large leakage flux, for instance. As a result of copper loss in the two windings, it is also less efficient.

Difference Between Autotransformer and Conventional Transformer

  1. An autotransformer uses self-induction because there is only one winding whereas a conventional transformer uses mutual induction.
  2. Autotransformers only have one winding which serves as both primary and secondary. On the other hand, conventional transformers have multiple windings.
  3. Autotransformers use less material for windings in comparison to conventional transformers which use more because they have multiple windings.
  4. When it comes to size, autotransformers tend to be smaller in size whereas conventional transformers tend to be larger.
  5. The output voltage in autotransformers is variable and in conventional transformers is constant.
  6. There is less impedance in autotransformers whereas conventional transformers tend to have higher impedance.
  7. Autotransformers are used as a stator in induction motors, voltage regulators in labs and train stations, etc. On the other hand, conventional transformers are used to increase and decrease the voltage in the power grid.

Comparison Between Autotransformer and Conventional Transformer

Parameters of ComparisonAutotransformerConventional Transformer
Induction PrincipleSelf-inductionMutual induction
WindingsOnly one windingMultiple windings
Material for WindingLess materialMore material
Output VoltageVariableConstant
ApplicationsVoltage regulators, as a stator, etc.In power grids.


  1. https://ieeexplore.ieee.org/abstract/document/5762931
  2. https://ieeexplore.ieee.org/abstract/document/7951721
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