(a) A $250 \mathrm{~kW}, 500 \mathrm{~V}, 600 \mathrm{rpm}$ dc generator is built with an armature diameter of 0.75 m and a core length of 0.3 m . The lap connected armature, has 720 conductors. Using the data obtained from this machine, determine the armature diameters core length. number of armature slots, armature conductors and commutator segments for a $350 \mathrm{~kW}, 440, \mathrm{~V}, 720 \mathrm{rpm} 6$ pole dc generator. Assume a square pole face with ratio of pole arc to pole pitch equal to 0.66 . The full load efficiency is 0.91 and the internal voltage drop is $4 \%$ of rated voltage. The diameter of commutator is 0.7 of armature diameter. The pitch of commutator segments should not be less than 4 mm . The voltage between adjacent segments should not exceed 15 V at no load.

Explanation

To determine the armature diameters, core length, number of armature slots, armature conductors, and commutator segments for the new machine, we need to use the given data from the original machine. We can calculate the armature diameters by dividing the original armature diameters by the ratio of the new power to the original power. We can calculate the core length by dividing the original core length by the ratio of the new power to the original power. We can calculate the number of armature slots by dividing the original number of armature slots by the ratio of the new armature diameters to the original armature diameters. We can calculate the armature conductors by dividing the original armature conductors by the ratio of the new armature diameters to the original armature diameters. We can calculate the commutator segments by dividing the original commutator segments by the ratio of the new armature diameters to the original armature diameters.

Explanation

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