VOLTAGE REGULATION OF TRANSFORMER

With constant voltage applied in primary, the secondary terminal voltage will decrease due to voltage drop across its internal resistance and leakage reactance.

Let ₀V₂ and V₂ be the secondary terminal voltages at no load and on load respectively. There are three kinds of voltage regulation, which are discussed below.

1.30.1 Inherent Voltage Regulation

The difference ₀V₂ – V₂ is known as inherent voltage regulation of the transformer.

1.30.2 Voltage Regulation Down

If inherent voltage drop is divided by ₀V₂, it is known as voltage regulation down. Mathematically, we can write

and also      

1.30.3 Voltage Regulation Up

If inherent voltage drop is divided by V₂, it is known as voltage regulation up. Mathematically, we can write it as

and also      

The secondary terminal voltage not only depends on load current but also on the power factor of the load. The regulation is said to be at full load provided V₂ is determined for full load and at specified power factor condition. V₂ drops more and more with increasing load current. For lagging power factor load, V₂ < E₂, the voltage regulation is positive. For leading power factor load, V₂ > E₂, the voltage regulation is negative.

To maintain constant secondary terminal voltage on load, the primary terminal voltage is adjusted. It is expected that voltage drop would be as small as possible. Therefore, the lesser the value of regula-tion, the better is the performance of a transformer.