1. EMF EQUATION OF TRANSFORMER
Lecture No. 4
By. Sajid Hussain Qazi

2. EMF EQUATION OF TRANSFORMER
Let, N1=Number of turns in primary N2=Number of turns in secondary Φm=Maximum flux in core in webers = Bm*A f= frequency of input a.c voltage in hertz

3. As shown in figure below flux increases from its zero value to its maximum value Φm in one quarter of the cycle i.e., 1/4f seconds,
Average rate of change of flux is;
, wb/sec or volts

4. Now, rate of change of flux per turn means induced emf per turn Average emf per turn= 4fΦm ,volt If flux varies sinusoidally, then r.m.s value of induced emf is obtained by multiplying the average value with form factor. Form Factor= r.m.s value/average value=1.11 r.m.s value of emf per turn = 1.11*4*f*Φm = 4.44*f*Φm ,volt

5. Now, r. m. s value of the induced e. m
Now, r.m.s value of the induced e.m.f in whole of the primary winding will be;
(induced e.m.f/turn) x no. of primary turns
E1= 4.44*N1*f*Bm *A, volt ---(i)
Similarly, r.m.s value of the induced e.m.f in whole of the secondary winding will be;
(induced e.m.f/turn) x no. of secondary turns
E2= 4.44*N2*f*Bm *A, volt ---(ii)
It is seen from equation (i and ii) that E1 /N1= E2/ N2= 4.44*f*Φm. It means that e.m.f/turn is same in both the primary and secondary windings.

6. Assignment Question-1
What down the construction and types of transformers?