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E.M.F. EQUATION OF AN ALTERNATOR OR AC GENERATOR.

Let,
P= No. of poles
Z= No. of Conductors or Coil sides in series/phase i.e. Z= 2T…Where T is the number of
 coils or turns per phase (Note that one turn or coil has two ends or sides)
f = frequency of induced e.m.f in Hz
ф = Flux per pole (Weber)
N = rotor speed (RPM)
Kd= Distribution factor =
Kc or KP = Cos α/2
If induced e.m.f is assumed sinusoidal then,
Kf= Form factor = 1.11
In one revolution of the rotor i.e. in  60/N seconds, each conductor is cut by a flux of Pф 
Webers.
dф= фP and also dt= secionds60/N
then induced e.m.f per conductor ( average) = dф/ dt= Pф/(60/N) =P N ф/60…..(a)
But We know that f = PN/120 or N= 120f/P
Putting the value of N in Equation (a)… We get the average value of e.m.f per conductor is
= Pф/60 x 120 f/P = 2f ф Volts.à{N= 120f/P}
If there are Z conductors in series per phase,
 then average e.m.f per phase = 2fфZ Volts= 4fфT Volts ….{Z=2T}
Also we know that Form factor= RMS Value/Average Value 
= RMS value= Form factor x Average Value,
= 1.11 x 4fфT = 4.44fфT Volts. ( Note that is exactly the same equation as the e.m.f equation
 of the transformer)
And the actually available voltage per phase = 4 Kc Kd fфT =4 KfKc Kd fфT Volts.
Note: If alternator or AC Generator is Star Connected as usually the case, then the
 Line Voltage is √3 times the phase voltage.
This is a copy right material. Don’t Copy and Past. 
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