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.
The +ve sign is for lagging p.f. and the –ve sign for leading p.f.
Condition for zero voltage regulation
The voltage regulation will be zero when the numerator is zero i.e.
The negative sign showed that zero regulation occurs at a leading power factor.
Its value is given by;
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
Sol. % regulation= (%R cosϕ+%X sinϕ)×100
For resistive load: 𝟇=0⁰
∴% regulation=3×1+6×0=3%=200×3/100=6 V
∴Terminal voltage=200-6=194 V