Question

A 25 kVA transformer has 400 tums on the primary and 50 tums in the secondary winding. The primary is connected to 2000 V, 50 Hz supply. Find the secondary EMF.
1. 100 V
2. 150 V
3. 250 V
4. 200 V

Answer 1

Correct Answer - Option 3 : 250 V

Concept:

• The transformer basically changes the level of voltages from one value to the other at a constant frequency.
• It is a static device that transforms electrical energy from one circuit to another without any direct electrical connection between them.
• This is achieved with the help of mutual induction between the two windings.
• In a transformer electrical energy changes to electrical and heat energy.

In a transformer, the relation between the number of turns, current, and voltages is given by:

\(n = \frac{{{N_1}}}{{{N_2}}} = \frac{{{V_1}}}{{{V_2}}}=\frac{I_2}{I_1}\)

N1 and N2 = number of turns in the primary and secondary windings respectively

V1 and I1 = Voltage and current respectively at the primary end

V2 and I2 = Voltage and current respectively at the secondary end

Calculation:

Given V1 = 2000 V, 50 Hz supply

N1 = 400

N2 = 50

\(\Rightarrow\frac{{{N_1}}}{{{N_2}}} = \frac{{{V_1}}}{{{V_2}}}\)

Putting on the respective values, we get:

\(\Rightarrow\frac{{{400}}}{{{50}}} = \frac{{{2000}}}{{{V_2}}}\)

V2 = 250 V

The frequency of the secondary generated voltage will be the same as the input frequency.