The no load ratio of a 50 Hz single-phase transformer is 2000/200 V. The maximum flux in the core is 0.05 Wb. What is the approximate number of primary turns?

Concept:

RMS value of induced EMF in whole primary winding (E1) = 4.44fN1Φm

RMS value of induced EMF in whole primary winding (E2) = 4.44fN2Φm

Where N1 = Number of turns in the primary winding

N2 = Number of turns in the secondary winding

Φm = Maximum flux in the core (in Wb)

f = Frequency of the AC supply (in Hz)

\(\frac{{{E_1}}}{{{N_1}}} = \frac{{{E_2}}}{{{N_2}}} = 4.44f{\phi _m}\)

This is called the emf equation of the transformer, which shows, the emf/number of turns is the same for both primary and secondary winding.

Calculation:

Given, E1 = 2000 V

E2 = 200 V

Φm = 0.05 Wb

We have E1 = 4.44fN1Φm

\(N_1=\frac{E_1}{4.44f\Phi_m}\)

Substituting the given values in the above equation we get,

\(N_1= \frac{2000}{4.44\times50\times 0.05}\)

N1 = 180