EMF Equation of Transformer :
Here is simple method to find out EMF Equation of Transformer:
Let N1 = No. of turns in primary
N2 = No. of turns in secondary
Øm = Maximum flux in core in webers = Bm x A
f = Frequency of a.c. input in Hz.
The flux increases from it's zero value to maximum value Øm in one quarter of the cycle i.e. in 1/4 f second.
Therefore, r.m.s value of e.m.f./turn = 4.44 Øm volts
Now, r.m.s value of induced e.m.f in the whole primary winding
= ( induced e.m.f. / turn ) x No. of primary winding
E1 = 4.44 f N1Øm ------------------- (i)
Similarly, r.m.s. value of e.m.f. induced in secondary is,
E2 = 4.44 f N2Øm ------------------- (ii)
From the above equations (i) and (ii), we get
E2/E1 = N2/N1 =k
the constant 'K' is called voltage transformation ratio .
1. If N2>N1 i.e. K>1 ,then transformer is called STEP-UP transformer .
2. If N2<N1 i.e. K<1 ,then transformer is called STEP-DOWN transformer .
