Introduction to Three Phase Transformer

Hello everyone, hope you guys are doing great. In this tutorial, I’m going to give you’re an elaboration on Introduction to Three Phase Transformer, its construction, major features. The detailed discussion on the windings will also be the part of this tutorial. The real life applications associated with such transformer will also be provided. The schematic diagram along with its circuit diagram will be given in order to get the better understanding. Moreover, the basic and important part of this discussion will be the working of a three phase transformer. I’ll let you guys know more about it in the later section. So, let’s get started with the Introduction to Three Phase Transformer.

Introduction to Three Phase Transformer

The three phase transformer can be built just by winding three single phase transformers on the single core. It is basically an iron core having three legs. Every leg has both primary and secondary windings respectively. In three phase transformers, most of the power is dissipated as three phase alternating current. Is most of the power generation companies, power is generated with the rotation of three different windings or coils by the inner magnetic field of that particular generator. These windings are separated by 120 degrees from each other. Power is generated when they rotate in the presence of the magnetic field.

Three phase transformers are usually used for stepping up and down the higher level of voltages at the different stages of a power transmission system. Power generation at grid stations is the three phase power to be transmitted along long transmission lines. Three phase power is normally generated at either 6kV or 11kV. The power is transmitted at higher voltage levels in order to reduce the line loses. Power is usually transmitted at 132kV or 400kV along the transmission lines. The step up transformer is used to step up the voltage at the higher levels. These higher voltages are then stepped down at the customer end according to the requirements. The voltages are normally stepped down to the levels of 400V or 230V.

Three phase transformer

Circuit Diagram

The circuit diagram helps in understanding all the components of the transformer. The circuit diagram is below:

general Circuit diagram of three phase transformer
Circuit Diagram of Three Phase Transformer

Three Phase Transformer Construction

Three phase transformers can be made by two methods as shown below.

  • Bank of three single phase transformers
  • Single unit of three phase transformers

Connections of Three Phase Transformer

Two types of windings as given below.

  • Star Winding
  • Delta Winding

The visual display of both star and delta connection is shown below.

star delta connection of transformer
Connections of three phase transformer

Turns Ration for both Connections

The turn ration is different for both star and delta connection. The turn ration for star-delta connection can be represented by the expression shown below.

Turn Ratio =n = \frac{N_p}{N_s}=\frac{ V_p}{ \sqrt{3} \times V_s}

The expression for the delta-star connection is shown below.

Turn Ratio = n = \frac{N_p}{N_s}= \frac{\sqrt{3} \times V_p}{V_s}

Advantages of Three Phase Transformer

The advantages associated with the electrical components shows their reliability as well as quality of work. The major advantage of three phase transformers is:
For the same kVA rating, it is smaller in size, cost effective lighter in weight in comparison to the three individual single phase transformers connected together.

Applications of Three Phase Transformer

The major applications associated of the three phase transformers include their uses as:

Power transformers
Distribution transformers
In electrical grids.

This is all from today’s tutorial on Introduction to Three Phase Transformer. I hope you enjoyed the discussion. I’ll be back with some more interesting topics soon. Meanwhile, if you guys have any sort of query, you can ask us in comments. Our team will surely respond you. Take care 🙂

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Muhammad Nashit

Electrical Engineer with exceptional problem solving and troubleshooting skills having over 2 years of professional industrial experience. Primarily focused on understanding of Electrical Drawings, Projects Planning and Monitoring. Excellent writing skills with good communication abilities and possess a wide range of technical skills. Both theoretical as well as practical understanding of Electrical Equipment.

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