Apr 15, 2014

EMF Equation of a Generator



Generator EMF Equation

Let φ =flux/pole in weber.
Z=total number of armature conductors = No. of slots * No.of conductors/slot.
P = No. of poles.
A = No. of parallel paths in armature.
N = armature rotation in rpm. 
E = EMF induced in any parallel path in armature. 
Generated EMF = e.m.f. generated in one of the parallel paths.
Average EMF generated/conductor = (dφ/dt) volt.   

Now, flux cut/conductor in one revolution, dφ = (φ*P) web.
Number of revolution per second = N/60;
Then, time for one revolution, dt = 60/N second.
Hence according to Faraday's laws of electromagnetic induction,

EMF generated/conductor= (dφ/dt) = (φZPN/120) Volt. 

For a wave-wound generator

No. of parallel paths is 2
No. of conductors (in series) in one path = Z/2

For a lap-wound generator

No. of parallel paths = P
No. of conductors (in series) in one path = Z/P

Then, EMF generated/path = [(φPN/60)*(Z/P)] = (φZN/60) Volt.
In general, generated EMF = [(φPN/60)*(Z/A)]= (φZPN/60A) Volt

Where    A=2 for wave-winding.
         A= P for lap-winding.


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