We know that in a synchronous generator or alternator when the conductors of the rotor cuts the alternating magnetic flux lines produced by the stator or field winding an EMF will induce in the rotor conductors ( according to the faraday's law ). Eventually, this emf circulates currents through the rotor conductors. Let us see the expression for induced emf in the rotor conductors.
EMF Equation of Synchronous Generator :
Let, Z_{ph} = Number of conductors in series / phase
= 2 T, where T is the number of turns / phase  P = Number of poles
 Ï† = Useful flux per pole in weber
 f = Frequency of the induced emf equal to NP / 120 Hz

N = Rotational speed in rpm
 K_{c} or K _{p} = Pitch or chrding or coil span factor = Cos Î±/2
 K_{d} or K_{b}
= Distribution factor / breadth factor
 K_{f} = Form factor = 1.11 for sinusoidal emf.
= 2 T, where T is the number of turns / phase
Total flux cut to complete one revolution = P Ï† Wb
Time taken to complete one revolution = 60 / N sec
According to faraday's law of electromagnetic induction average emf induced / conductor,
Average emf induced / phase = 2 f Ï† Z_{ph} = 4 f Ï† T volt
RMS value of emf / phase = Average value of emf / phase * Form factor
= 1.11 × 4 f Ï† T
= 4.44 f Ï† T volt
If pitch factor K_{c} and distribution factor K_{d} are considered then the actual emf induced will reduce.
Actually induced emf / ph = 4.44 K_{c} K_{d} f Ï† T volt
E_{ph} = 4 K_{f} K_{c} K_{d}
f Ï† T volt