A step-down transformer is used on a 2.2 kV line to deliver 110 V. How many turns are on the primary windings if the secondary has 25 turns?
A.
20
B.
250
C.
200
D.
500
Correct answer is D
Ep = 2.2kV = 2200V; Es=110V; Ns=25; Np=?
=\(\frac{E_p}{E_s}\) = \(\frac{N_p}{N_s}\)
= \(\frac{2200}{110}\) = \(\frac{N_p}{25}\)
=110 × Np = 2200 × 25
=\(N_p\) = \(\frac{55,000}{110}\)
∴\(N_p\) = 500 turns
