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What is the voltage regulation of power transformer?
5 - 8%
6 - 10%
10тИТ12%
10тИТ15%
6 - 10%
Voltage regulation of a power transformer is defined as the change in secondary terminal voltage from no-load to full-load, expressed as a percentage of the rated secondary voltage. For standard power transformers, this value typically ranges between 6% and 10% depending on the power factor of the load.
Voltage regulation of a power transformer is defined as the change in secondary terminal voltage from no-load to full-load, expressed as a percentage of the rated secondary voltage. For standard power transformers, this value typically ranges between 6% and 10% depending on the power factor of the load.
%VR=VFLтАЛVNLтАЛтИТVFLтАЛтАЛ├Ч100 тАФ The percentage voltage regulation formula
VNLтАЛтЙИV2тАЛ+I2тАЛ(ReтАЛcos╧Х┬▒XeтАЛsin╧Х) тАФ Approximate voltage drop model
The regulation occurs due to the internal impedance (resistance and leakage reactance) of the transformer windings. When current flows through the primary and secondary windings, I2R and IX drops occur within the transformer. Consequently, the secondary terminal voltage drops as load current increases, represented as the difference between no-load voltage and full-load voltage normalized by the rated load voltage.
Voltage regulation depends heavily on the load power factor (leading, lagging, or unity).
A lower percentage regulation value is preferred as it indicates a more stable output voltage.
For leading power factors, the regulation can be negative (the secondary voltage rises under load).
Power transformers are designed with low impedance to minimize this regulation for efficiency.
Ensures stable supply voltage for sensitive equipment
Reduces the need for frequent tap changing
Lower internal impedance increases fault current levels
Requires careful design considerations for electromagnetic forces
Grid distribution substations
Industrial power transmission systems
Power transformers (large capacity) usually have stricter regulation requirements compared to small distribution transformers.
Option B (6-10%) represents the standard industrial operating range for large power transformers under normal load conditions.
B is correct тАФ The typical voltage regulation for power transformers is between 6% and 10%, reflecting the necessary voltage drop compensation for standard load profiles.
Always remember that at leading power factor, the voltage regulation can become negative, meaning the secondary voltage increases at full load compared to no-load.