Question

A step down transformer converts transmission line voltage from $11000V$ to $220V$. The primary of the transformer has $6000$ turns and efficiency of the transformer is $60\%$. If the output power is $9kW$, then the input power will be

• A. $11kW$
• B. $12kW$
• C. $14kW$
• D. $15kW$

Answer 1

Answer: (D)

Here,
$V_p=11000V$,
$V_s=220V$
$N_p=6000$,
$\eta =60\%;$
$P_0=9kW=9\times 10^{3}W$
Efficiency, $\eta =\frac{Outputpower}{Inputpower}=\frac{P_o}{P_i}$
$\therefore P_i=\frac{P_o}{\eta }$
$=\frac{9\times 10^3}{60/100}$
$=1.5\times 10^4<br/>=15kW$