A transformer is to be designed to increase the 30 kV-rms output of a generator to the transmission-line voltage of 345 kV-rms. If the primary winding has 80 turns, how many turns must the secondary have?
A) 6
B) 70
C) 920
D) 9200
E) 12

Question

Quizplus · Accepted Answer

We can use the transformer turns ratio equation: 
$$\frac{V_p}{V_s}=\frac{N_p}{N_s}$$
Where $V_p$ is the primary voltage, $V_s$ is the secondary voltage, $N_p$ is the number of turns in the primary winding, and $N_s$ is the number of turns in the secondary winding. 
Plugging in the given values, we get: 
$$\frac{30	ext{ kV}}{345	ext{ kV}}=\frac{80}{N_s}$$
Solving for $N_s$, we get:
$$N_s=\frac{80	imes 345	ext{ kV}}{30	ext{ kV}}=920$$
Therefore, the answer is C, 920.

A Transformer Is to Be Designed to Increase the 30