## What is Voltage Regulation ?

The voltage regulation is the percentage of voltage difference between no load and full load voltages of a transformer with respect to its full load voltage.

### Explanation of Voltage Regulation of Transformer

Say an electrical power transformer is open circuited, means load is not connected with secondary terminals. In this situation, the secondary terminal voltage of the transformer will be its secondary induced emf E_{2}. Whenever full load is connected to the secondary terminals of the transformer, rated current I_{2} flows through the secondary circuit and voltage drop comes into picture. At this situation, primary winding will also draw equivalent full load current from source. The voltage drop in the secondary is I_{2}Z_{2} where Z_{2} is the secondary impedance of transformer.

Now if at this loading condition, any one measures the voltage between secondary terminals, he or she will get voltage V_{2} across load terminals which is obviously less than no load secondary voltage E_{2} and this is because of I_{2}Z_{2} voltage drop in the transformer.

#### Expression of Voltage Regulation of Transformer

Expression of **Voltage Regulation of Transformer**, represented in percentage, is

### Voltage Regulation of Transformer for Lagging Power Factor

Now we will derive the expression of voltage regulation in detail. Say lagging power factor of the load is cosθ_{2}, that means angle between secondary current and voltage is θ_{2}.

Here, from the above diagram,

Angle between OC and OD may be very small, so it can be neglected and OD is considered nearly equal to OC i.e.**Voltage regulation of transformer** at lagging power factor,

### Voltage Regulation of Transformer for Leading Power Factor

Let’s derive the expression of voltage regulation with leading current, say leading power factor of the load is cosθ_{2}, that means angle between secondary current and voltage is θ_{2}.

Here, from the above diagram,

Angle between OC and OD may be very small, so it can be neglected and OD is considered nearly equal to OC i.e.**Voltage regulation of transformer** at leading power factor,