Transformer Taps on High Voltage Side Why?

This article describes the reasons for providing the transformer taps on the high voltage side. So let’s begin with the basic introduction of an electrical transformer.

An electrical transformer or simply transformer is a static electrical machine that is used to increase or decrease the voltage level in the ac supply system. Therefore, a transformer is one of the most significant parts of a power system, and it is used for power transmission and distribution at different voltage levels.

What is Transformer Tapping?

Transformer tapping is an electrical connection brought outside from any point between the two main terminals of the transformer winding.

In a transformer, tapping is provided to change the voltage level when a load is connected to it. Tapping is more often in power transformers. When a transformer is operating and if there is any change in the output voltage of the transformer, we need to regulate the output to get the desired voltage. This task is accomplished by using transformer tapping.

transformer tappping on hv side

Basically, the transformer tap changer changes the number of turns in the circuit to produce the desired output voltage at the secondary side of the transformer. The internal circuit of the transformer tap changer is shown in Figure 1.

Types of Transformer Tap Changers

There are two types of transformer tap changers namely-

  • On-Load Tap Changer
  • Off-Load Tap Changer

The transformer tappings are practically provided on the high-voltage side of the transformer. Let us discuss the actual reason behind this.

Why Tapings are Provided on High Voltage Side of the Transformer?

In practice, we notice that in large transformers (usually power transformers), the tapings are provided on the high-voltage side due to the following reasons-

  • Reason 1 – In large transformers, the high-voltage winding is provided over the low-voltage winding. Therefore, it is easily accessible. Hence, it is quite easy to provide tappings on the high-voltage winding.
  • Reason 2 – The value of the current in the high-voltage winding is lower than the current in the low-voltage winding. Therefore, the provision of tappings on the high voltage side gives fewer sparks and hence less wear to the tap changer contacts.
  • Reason 3 – The transformer’s high voltage winding has more turns than low voltage winding. Therefore, we can get more tapping points on the high-voltage side and regulate the output voltage in a wider range.


Actually, there is no hard and fast rule to provide the transformer tappings on the high voltage side. Because, we can create tappings on both the high voltage side and low voltage, but we always examine their technical benefits.

The technical analysis of different-sized transformers concludes that in small transformers like 240V/12V, and 240V/24V, tappings are provided on the low-voltage side. Whereas, in large transformers such as power transformers and distribution transformers, the tappings are provided on the high voltage side of the transformer.

In small transformers, the reasons behind providing tappings on the low-voltage side are as follows

  • In a small transformer, the low-voltage winding is wound over the high-voltage winding. Thus, it is easier to provide tappings on the low-voltage side.
  • The current in the low voltage winding of a small transformer is not much significant to create a spark.


Hence, this is all about the reasons for transformer tapping on the high-voltage side. From the above discussion, it is clear that the transformer tapping are provided on that winding which is easily accessible and carries less current.

The tapping on hv in power transformer is provided because of the following reasons.

  1. HV has a large number of turns, therefore we can get the fine voltage variation.
  2. HV winding carries low current. It is easy to interrupt low current.
  3. HV is on the exterior side because of insulation consideration, hence it is easily accessible.
  4. Better voltage regulation

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