- 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 is the change in voltage from the sending end to the receiving end of a component. In power work it is the percent difference between no-load and full-load voltage on distribution lines, transmission lines and transformers.
Explanation of Voltage Regulation of Transformer
If an electrical power transformer is open-circuited, with no load on the secondary, the secondary terminal voltage of the transformer is the secondary induced EMF, E2.
Connect full load to the secondary and rated current I2 flows. Voltage drop then appears. The primary also draws the matching full-load current from the source. The voltage drop in the secondary is I2Z2 where Z2 is the secondary impedance of transformer.
On load, the voltage between the secondary terminals is V2. That loaded voltage sits below no-load secondary voltage E2 by the I2Z2 drop.
Expression of Voltage Regulation of Transformer
The voltage regulation of transformer, in percent, is
Voltage Regulation of Transformer for Lagging Power Factor
Now derive the same quantity in detail. Let the lagging power factor of the load be cosθ2, so the angle between secondary current and voltage is θ2.
From that diagram,
The angle between OC and OD is small enough to ignore, so OD is taken as equal to OC:
Voltage regulation of transformer at lagging power factor is
Voltage Regulation of Transformer for Leading Power Factor
Now derive the same quantity with leading current. Let the leading power factor of the load be cosθ2, so the angle between secondary current and voltage is θ2.
From that diagram,
The angle between OC and OD is small enough to ignore, so OD is taken as equal to OC:
Voltage regulation of transformer at leading power factor is
Zero Voltage Regulation of A Transformer
‘Zero voltage regulation’ means no-load voltage equals full-load voltage, so the regulation equation gives zero. That case is not practical. It exists only as theory for an ideal transformer.
