(a) Calculate the main dimensions, number of poles and air gap length of a $500 \mathrm{~V}, 600 \mathrm{KW}, 900 \mathrm{rpm}$ dc generator with following data : average gap density $0.6 \mathrm{wb} / \mathrm{m}^{2}$, ampere conductors per m 35000 , ratio of pole arc to pole pitch is 0.70 , efficiency $91 \%$, gap contraction factor $1.15, \mathrm{mmf}$ for air gap $50 \%$ of armature mmf . The value of the following parameters must not exceed the value shown against each; peripheral speed $40 \mathrm{~m} / \mathrm{sec}$, frequency of flux reversal 50 Hz , current per brush arm 400 A ; armature mmf per pole 7500 A .

Explanation

The main dimensions, number of poles, and air gap length of a 500 V, 600 kW, 900 rpm dc generator are calculated using the given formulas and data.