elctrical machines

Derive from the first principles the equation of induced  E.M.F in armature windings of an alternator.                                                                                              

   (b) A 60-Kva 220V,50-Hz single phase alternator has effective armature resistance of 0.016Ω and an armature leakage reactance of 0.07Ω.Calculate the voltage induced in the armature when the alternator is delivering rated current at a load power factor of;

                    (i)Unity

                    (ii) 0.7 lagging

                    (iii) 0.7 leading

  (c)What  are the advantages of using fractional-pitch coils in the armature of an alternator.