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} = Φ_{1}/ Φ_{2} × N_{1}/N_{2}
Or 498/250 = 0.06/0.058 × 250/N^{2}
Or N^{2} = 130 rpm