Q. An 8 - pole dc generator has 500 armature conductors and has a useful flux per pole of 0.065 web. What will be the emf generated if it is lap connected and runs at 1000 r.p.m.  What must be the speed at which it is to be driven to produce the same emf if it is wave wound?  

Ans.

E₁   = N₁PΦZ/60A = 10000 × 0.065 ×500 ×  P/A

               For lap connection A = P

                       E₁  =  10000 × 0.065 ×500 /60 = 541.67 volts

                       E₂  = N₂8ΦZ/60 × 2

 Since                  E₂  = E₁

                             8N₂ΦZ/60 × 2 = 8N₁ΦZ/60 × 8

                       N₂ = N₁ × 2/8 = 1000 × 2/8 = 250 rpm