Question

A 3VA, 230/12V, 50 Hz single phase transformer has 100 secondary turns. Assuming the transformer to be ideal, Determine
i) The primary current
ii) The secondary current
iii) The number of primary turns

Answer 1

Given that,

Power = 3 VA

Induced emf in primary winding = 230 V

Induced emf in secondary winding = 12 V

Frequency = 50 Hz

Number of turns in secondary = 100

(I). We need to calculate the primary current

Using formula of primary current

$I_{1}=\dfrac{P}{V_{1}}$

Put the value into the formula

$I_{1}=\dfrac{3}{230}$

$I_{1}=0.013\ A$

(II). We need to calculate the secondary current

Using formula of primary current

$I_{2}=\dfrac{P}{V_{2}}$

Put the value into the formula

$I_{2}=\dfrac{3}{12}$

$I_{2}=0.25\ A$

(III). We need to calculate the number of primary turns

Using formula of number of primary turns

$N_{1}=\dfrac{V_{1}}{V_{2}}N_{2}$

Put the value into the formula

$N_{1}=\dfrac{230}{12}\times100$

$N_{1}=1917$

Hence, (I). The primary current is 0.013 A

(II). The secondary current is 0.25 A.

(III). The number of primary turns is 1917.