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)

K

_{d}= Distribution factor =**K**

_{c }or K_{P}= Cos α/2If induced e.m.f is assumed sinusoidal then,

K

_{f}= Form factor = 1.11In 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

**=**….{Z=2T}*4fфT Volts*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 K

_{c}K_{d }fфT =*4 K*_{f}K_{c}K_{d }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.

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