Q. The armature of 6 -pole dc generator has a wave winding containing 664 conductors. Calculate the generator emf when flux per pole is 0.06 weber and the speed is 250 rpm. At what speed must the armature be driven to generator an emf of 250 V. If the flux per pole is reduced to 0.058 weber.

  Sol.  Given P = 6; A = 2 (as wave wound); Z = 664    Φ = 0.06,       N = 250 rpm

           Thus    E_g = PΦZN/60A = 6/2 × 0.06 × 664 × 250/60 = 498V

           Now , given E_g = 250 V; Φ = o.o58 weber

            Then            N = ?

            Thus              E_g1/E_g2 = Φ₁/ Φ₂ × N₁/N₂

             Or               498/250 = 0.06/0.058 × 250/N²

              Or           N² = 130 rpm