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Daily Concept Booster Electrical Engineering: Voltage Regulation of Transformer

Voltage Regulation of Transformer

The voltage regulation of a transformer is the arithmetic difference (not phasor difference) between the no-load secondary voltage (  V02) and the secondary voltage V2 on load expressed as a percentage of no-load voltage i.e.

Daily Concept Booster Electrical Engineering: Voltage Regulation of Transformer |_40.1

The +ve sign is for lagging p.f. and the –ve sign for leading p.f.

Condition for zero voltage regulation

Daily Concept Booster Electrical Engineering: Voltage Regulation of Transformer |_50.1

The voltage regulation will be zero when the numerator is zero i.e.

Daily Concept Booster Electrical Engineering: Voltage Regulation of Transformer |_60.1

The negative sign showed that zero regulation occurs at a leading power factor.
Its value is given by;

Daily Concept Booster Electrical Engineering: Voltage Regulation of Transformer |_70.1

Example

Q1. A 10 kVA, 400 V/ 200 V, single-phase transformer with a percentage resistance of 3% and percentage reactance of 6% is supplying a current of 50 A to a resistive load. The value of the load voltage is
(a) 192 V
(b) 194 V
(c) 196 V
(d) 390 V

S1. Ans.(b)
Sol. % regulation= (%R cos⁡ϕ+%X sin⁡ϕ)×100
For resistive load: ?=0⁰
∴% regulation=3×1+6×0=3%=200×3/100=6 V
∴Terminal voltage=200-6=194 V

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