Electrical Machines Questions and Answers – Synchronous Machines
EMF Polygon – 2
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The chording angle for eliminating 5th harmonic should be __________
Correct!
Wrong!

In 48 slot, 4pole,3 phase alternator, the coilspan is 10. Its distribution and pitch factors are respectively ___________
Correct!
Wrong!

Which among the given harmonics are called belt harmonics?
Correct!
Wrong!

For eliminating nth harmonic from the EMF generated in the phase of a 3phase alternator, the chording angle should be
Correct!
Wrong!

Consider the following statements:
(i) breadth factor for third harmonic k_{d3} is more than that for fundamental k_{d1}
(ii) k_{d3} < k_{d1}
(iii) k_{d3} may be less or more than k_{d1} depending upon the number of slots and poles
(iv) coilspan factor for third harmonic k_{p3}>k_{p1} (coil span factor for fundamental)
(v) k_{p3} < k_{p1}
(vi) k_{p3} may be less or more than k_{p1} depending upon the number of slots and poles
From these, the correct answer is
(i) breadth factor for third harmonic k_{d3} is more than that for fundamental k_{d1}
(ii) k_{d3} < k_{d1}
(iii) k_{d3} may be less or more than k_{d1} depending upon the number of slots and poles
(iv) coilspan factor for third harmonic k_{p3}>k_{p1} (coil span factor for fundamental)
(v) k_{p3} < k_{p1}
(vi) k_{p3} may be less or more than k_{p1} depending upon the number of slots and poles
From these, the correct answer is
Correct!
Wrong!

A 3phase, 4pole alternator has 48 stator slots carrying a 3phase distributed winding. Each coil of the winding is short chorded by one slot pitch. The winding factor is given by ___________
Correct!
Wrong!

A 6pole alternator with 36 slots carries a 2phase distributed winding. Each coil is short pitched by one slot. The winding factor is given by
Correct!
Wrong!

Machine A has 60° phase spread and machine B has 120° phase spread. Both the machines have uniformly distributed winding. The ratio of distribution factors of machine A to machine B is ___________
Correct!
Wrong!

The winding’s for a 3phase alternator are:
(i) 36 slots, 4 poles, span 1 to 8
(ii) 72 slots, 6 poles, span 1 to 10
(iii) 96 slots, 4 poles, span 1 to 21
The winding’s having pitch factor of more than 0.97 are
(i) 36 slots, 4 poles, span 1 to 8
(ii) 72 slots, 6 poles, span 1 to 10
(iii) 96 slots, 4 poles, span 1 to 21
The winding’s having pitch factor of more than 0.97 are
Correct!
Wrong!
