Determine the main dimensions, number of poles and the length of air…

Question

Determine the main dimensions, number of poles and the length of air gap of a 600 KW, 500V, 900 rpm generator. Assume average gap density as $0.6 \text{ Wb/m}^2$ and ampere conductors per meter as 35000. The ratio of pole arc to pole pitch is 0.75 and the efficiency is 91 percent. The design constrains are: peripheral speed $\le 40 \text{ m/s}$, frequency of flux reversals $\le 50$, current per brush arm $\le 400$, and armature mmf per pole $\le 7500 \text{A}$. The mmf required for air gap is 50 percent of armature mmf and gap contraction factor is 1.15.