An emf is induced in a DC generator, when a conductor is rotated in a magnetic field. The emf induced in a conductor depends on the speed of rotation of the conductor and the flux produced from a field winding.
Let P = number of poles.
Z = total number of conductor in the armature.
A = number of parallel paths, into which the conductors are grouped. So each parallel path will have Z/A conductor in series.
N = speed of the rotor in revolution per minute(rpm)
N/60 = Speed of the rotor in revolutions per second.
Time taken by the rotor to complete one revolution, dt = 1/(N/60)= 60/N second
In one revolution of the rotor, the total flux Φ cut the by each conductor in the stator poles, dΦ = ΦP weber
By faraday’s law of electromagnetic induction, the emf induced is proportional to rate of change of flux.
Since there are Z/A conductor in series in each parallel path, the emf induced is given by
The above equation represents the general equation for emf induced in a DC generator. The armature conductors in a DC generator can be connected in two ways. They are lap winding and wave winding.
For lap wound machines, the number of parallel paths is equal to the number of poles(A = P).
For such machine, the emf equation is given by,
In wave wound machine, the number of parallel paths is equal to 2(A = 2).
The emf equation of a wave wound machine is given by,
If a DC generator has 8 poles and the flux produced is 0.025 weber. The generator has 450 conductors in the armature and rotates at 1500 rpm,
the EMF generated by the Lap wounded DC generator is
the EMF generated by the wave wounded generator is