Hey, today we are going to know why we need Vector Grouping in Three-Phase Transformer. I noticed that most of the students don't know, what is the actual need of vector grouping in the transformer even after reading many things about vector grouping. So, today we are going to know the actual practical reason.

## Vector Group of Transformer

Vector Grouping is a theoretical approach to identify or understand the nature of the connection between three phases of the primary and secondary winding along with the phase shift between the primary and secondary winding voltage of a three-phase transformer.

For example, 'Dyn11' implies that,

'D' indicates the high voltage winding of the transformer is Delta connected.

'y' indicates the low voltage winding of the transformer is Star connected.

Here, 'n' indicates that a terminal is brought out from the Star point of the star connection or in simple word it has a neutral terminal.

'11' indicates that the phase shift between the high voltage and low voltage winding is 30 degree leading.

Remember that,

This vector representation does not give an indication for the primary and secondary winding. You may think that 'D' written in first so the primary winding is delta connected. That's wrong. According to the IEC60076-1 standard, the HV-LV sequence should be maintained.
So, here 'D' written in first because it indicates the HV winding. It may secondary winding.

## Why there are different types of Vector Groups?

You may think that why there are different types of vector groups. In a three-phase transformer, there are three windings in primary side and three windings on the secondary side. So we have 6 terminals on the primary side and 6 terminals on the secondary side, but we need only 3 terminals from both primary and secondary sides.

So, we can make one single primary winding by connecting internally all three windings of the primary side and we can make one single secondary winding by connecting internally all three windings of the secondary side.

We can connect those winding in Star or Delta configuration. So there are different types of connection sequence is possible.

For example, we can connect all three windings of the primary side in the delta configuration and
all three windings of the secondary side in the star configuration. In this case, the phase difference between the primary and secondary winding will be 30 degrees. You can see the diagram below.

So, the phase difference in a transformer depends upon those types of connections, that's why different types of vector groups are available.

In, simple word, the different types of vector groups depends upon the different types of the connection sequence of the windings.

## Why we need Vector Grouping in Three-Phase Transformer?

The vector group of a transformer indicates what type of connection is made between the windings of that transformer. It also indicates what is the phase difference between the primary and secondary winding voltage of that transformer.

So we must know the vector group when connecting two or more transformers in parallel. Because if we connect two transformers of different vector groups in parallel, a large amount of circulating current will flow between those two transformers which will affect the transformers and their working.

If we do not know the vector group of a transformer, then we cannot find out the no-load current, iron loss properly.

If we do not know the vector group of the transformer, then we also cannot draw the proper input, output voltage, and current waveforms.