Introduction and Advantages of Three Phase Transformer

Introduction to Three Phase Transformer

• The generation of an electrical power is usually three phase and at higher voltages like 13.2 kV, 22 kV or somewhat higher. Similarly transmission of an electrical power is also at very high voltages like 110 kV, 132 kV or 400 kV. To step up the generated voltages for transmission purposes it is necessary to have three phase transformers. At the time of distribution it is necessary to reduce the voltage level upto 6600 V, 440 V, 230 V etc. For which step down three phase transformers are essential. Thus three phase transformers proves to be economical in transmission and utilization of electrical energy.

• Previously it was a common practice to employ suitably interconnected three single phase transformers than to have a single three phase transformer which is popular now a days and used widely. In a single three phase transformer there is improvement in design and manufacture.

1. Advantages of Three Phase Transformers

• Some of the advantages of a single three phase transformer are as follows:

1. A three phase transformer occupies less space for same rating, compared to a bank of three single phase transformers.

2. It weighs less.

3.Its cost is less.

4. Only one unit is required to be handled which makes it easy for the operator.

5.It can be transported easily.

6. The core will be of smaller size and the material required for the core is less.

7. Single three phase unit is more efficient.

8. In case of three single phase units, six terminals are required to be brought out while in case of one three phase unit, only three terminals are required to be brought out.

9. The overall busbar structure, switchgear and installation of single three phase unit is simpler.

• In contrast to above, a bank of three single phase transformers is used in underground work such as in mines as it is easier to transport these units. The bank of three single phase transformers also offers the advantage of open delta operation with reduced rating when one of the units in the bank is inoperative.

• But it is common practice to use a single three phase transformer unit due to its reduced cost.

Review Question

1. State the advantages of three phase transformer.