Question

A step up transformer operates on a $220 \,V$ line and supplies to a load of a current of $2 \,A$. The ratio of turns in primary and the secondary winding is $25 : 1$. The secondary voltage, primary current and power output will be respectively

• A. 5500 V, 50 A,11 kW
• B. 500 V, 25 A, 22 kW
• C. 2400 V, 40 A, 5.5 kW
• D. None of the above

Answer 1

Answer: (A)

The transformation ratio for a transformer is given by
$\frac{I_{p}}{I_{s}}=\frac{e_{s}}{e_{p}}=\frac{N_{s}}{N_{p}}=K$
where $I_{p}, N_{p}, e_{p}$ are current, number of turns and voltage across primary and $I_{s}, N_{s}, e_{s}$ across secondary, respectively.
Given, $e_{p}=220\, V , I_{s}=2\, A$
$k =\frac{N_{p}}{N_{s}}=25 $
$\Rightarrow e_{s} =\frac{N_{s}}{N_{p}} \times e_{p}$
$=25 \times 220=5500\, V $
and $ I_{p} =\frac{N_{s}}{N_{p}} \times I_{s}$
$=25 \times 2=50 \,A$
Power output $=e_{s} I_{s}$
$=5500 \times 2=11000 \,W$
$1 \,kW =10^{3} W $
$ \therefore $ Power output $=11 \,kW$