Working Principle of Transformer

Ideal Transformer

EMF Equation of Transformer

Theory of Transformer

Leakage Reactance of Transformer

Equivalent Circuit of Transformer

Voltage Regulation of Transformer

Losses in Transformer

Open and Short Circuit Test on Transformer

Tertiary Winding of Transformer

Parallel operation of Transformers

Core of Transformer

Transformer Insulating Oil

Dissolved Gas Analysis of Transformer Oil

Transformer Cooling System

Transformer Accessories

• Conservator Tank of Transformer

• Buchholz Relay in Transformer

• Silica Gel Breather

• Radiator of Transformer

• Magnetic Oil Gauge or MOG

• Temperature Indicators of Transformer

• On and No Load Tap Changer

Auto Transformer

Three phase transformer

Current Transformer

Voltage Transformer

• Accuracy Limit & Instrument Security Factor

• Knee Point Voltage of Current Transformer

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Explanation of Voltage Regulation

• Expression

Voltage Regulation for Lagging Power Factor

Voltage Regulation for Leading Power Factor

## 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 & 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 & 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,