Which side of Transformer is provided for Tapping and Why?

Transformer Tapping

A transformer is an electrical machine which is used to step up or step down the voltage level. Transformers are used for transmission purposes as well as distribution purposes of electrical power. Transformer Tapping is very important you should know. In this post, we will discuss the Transformer Tapping and also Which side of the Transformer is provided for Tapping and Why?

What is Transformer Tapping?

When a no. of connections are brought outside from any points between the terminals of the transformer winding maintaining a distance then it is called Transformer Tapping.

Why we need Tapping on the Transformer?

We know that a transformer has two voltage ratings one is a primary side voltage rating and the other is a secondary side voltage rating. In the step-down transformer, the primary side voltage rating is more than the secondary side but in the step-up transformer, the primary side voltage rating is less than the secondary side.
The primary and secondary voltage ratio depends on the turn ratio of the transformer. When a transformer is connected in supply it gives a particular fixed voltage as the output. But sometimes we need a different voltage level.

According to the above equations, we can vary the secondary voltage by changing the turn ratio and the turn ratio can be varied by changing the no. of turns of any winding. So to get the desired output voltage level the tapping is provided on the transformer.

The changing of no. of turns sequence is,

1. If we increase the no. of turns of the primary winding then the secondary voltage will be decreased.
2. If we decrease the no. of turns of the primary winding then the secondary voltage will be increased.
3. If we increase the no. of turns of the secondary winding then the secondary voltage will be increased.
4. If we decrease the no. of turns of the secondary winding then the secondary voltage will be decreased.

Which side of the Transformer is provided for Tapping?

Actually, if you ask that which side of the transformer is used for tapping then I will say both high voltage and low voltage sides, because you may notice in smaller transformers (like 240/12V, 240/24V) tappings are provided on low voltage side but in case of large transformers, tappings are provided on the high voltage side of the transformer. let's know the reasons.

Why tappings are provided on the high-voltage side of the transformer?

There are some reasons for tapping on the high voltage side of the large transformer which are,

1. In large transformers, the high voltage(HV) winding is generally wound over the low voltage (LV)winding for insulation-saving purposes. So it is easier to provide the tapping on the high-voltage side instead of the low-voltage side. 
2. As the no. of turns of the high voltage winding is more than low voltage winding so there is a facility to make more on. of Tappings than low voltage side.
3. As we know the current on high voltage winding is always less than low voltage winding so the tapping on the high voltage side gives low sparking and less Wear on tap changer contacts.

In the case of smaller-size transformers, the tapping is provided on the low voltage side because,

1. Low Voltage winding is wound over on high voltage winding.
2. The current of low voltage winding is not sufficient to create sparking or ARC.

Read Also:

• [Explained] Transformer Size VS Frequency
• Identify Transformer Primary Secondary High Low Voltage Side
• [BEST] Applications, Advantages, Disadvantages of Isolation Transformer
• Why Current, Voltage changes But Power, Frequency constant in Transformer?
• [Three Reasons] Why Transformer is Rated in KVA
• Why we need Vector Grouping in Three Phase Transformer?

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