- Voltage Regulation Definition: Voltage regulation is a measure of the voltage change between no load and full load in electrical components, including transformers.
- Transformer Voltage Drop: When a transformer is loaded, the secondary terminal voltage drops due to impedance, causing a difference from the no-load voltage.
- Voltage Regulation Formula: The voltage regulation of a transformer is calculated as a percentage using the formula involving load and impedance.
- Lagging Power Factor Impact: With a lagging power factor, the current lags behind the voltage, affecting the voltage regulation of the transformer.
- Leading Power Factor Impact: With a leading power factor, the current leads the voltage, also impacting the transformer’s voltage regulation.
What is Voltage Regulation?
Voltage regulation measures the change in voltage between the sending and receiving ends of a component. In power engineering, it describes the percentage voltage difference between no load and full load conditions in distribution lines, transmission lines, and transformers.
Explanation of Voltage Regulation of Transformer
If an electrical power transformer is open-circuited (load not connected to the secondary terminals), the voltage at the secondary terminal voltage of the transformer will be the secondary induced emf, E2.
Whenever a full load is connected to the secondary terminals of the transformer, rated current I2 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 I2Z2 where Z2 is the secondary impedance of transformer.
Under this load condition, measuring the voltage between the secondary terminals gives V2, which is less than the no-load secondary voltage E2 due to the I2Z2 voltage drop in the transformer.
Expression of Voltage Regulation of Transformer
The equation for the 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 cosθ2, that means angle between secondary current and voltage is θ2.
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 cosθ2, that means angle between secondary current and voltage is θ2.
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,
Zero Voltage Regulation of A Transformer
‘Zero voltage regulation’ means there is no difference between the no-load voltage and the full-load voltage. In the voltage regulation equation, this would mean the voltage regulation is zero. This is not practical and is only theoretically possible for an ideal transformer.
