EMF EQUATION OF TRANSFORMER Lecture No 4 By

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

EMF EQUATION OF TRANSFORMER Let, webers hertz N 1=Number of turns in primary N 2=Number of turns in secondary Φm=Maximum flux in core in = Bm*A f= frequency of input a. c voltage in

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

Now, rate of change of flux per turn means induced emf per turn Average emf per turn= 4 fΦm , 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

�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 E 1= 4. 44*N 1*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 E 2= 4. 44*N 2*f*Bm *A, volt ---(ii) �It is seen from equation (i and ii) that E 1 /N 1= E 2/ N 2= 4. 44*f*Φm. It means that e. m. f/turn is same in both the primary and secondary windings.

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