EMF Equation of DC Generators

Φ= useful flux per pole in webers (Wb)

P= total number of poles

Z= total number of conducor in the armature

n= speed of rotation of armature in revolutions per second (r.p.s)

A= number of parallel paths though the armaure between brushes of opposite polarity

$\frac{Z}{A}$= number of armature conductors in series for each parallel path

$E = np\Phi \times \frac{Z}{A}$

$E = \frac{{np\Phi Z}}{A}$  --------------- (1)

Equation (1) is called e.m.f  equation of a d.c machine.