Electrical Machines Questions and Answers_pag130

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by Manish 
5-6 minutes 
 
 
This set of Electrical Machines Multiple Choice Questions & Answers (MCQs) focuses on “EMF 
Polygon – 1”. 
1. The angular slot pitch, γ is given by 
a) γ= πP/Total number of slots Elect radians 
b) γ= 180P/Total number of slots Elect degrees 
c) γ= 180/Slots per pole Elect degrees 
d) Any of the mentioned 
View Answer 
Answer: d 
Explanation: Angle γ is the angle between adjacent slots. 
2. Consider the following statements regarding the design of distributed armature winding in a 
3-phase alternator: 
(i) it reduces the phase-belt harmonics 
(ii) it increases the utilization of the armature iron and copper 
(iii) it increases rigidity and mechanical strength of the winding 
(iv) it reduces copper in the overhang of the winding 
Which of these statements are correct? 
a) (i),(iii),(iv) 
b) (ii),(iii),(iv) 
c) (i),(ii),(iii) 
d) (i),(ii),(iii),(iv) 
View Answer 
Answer: c 
Explanation: Distributed armature winding does not reduce copper in the overhang of the 
winding, also k​dn​=(sinqnγ/2)/(qsinnγ/2), k​dn​d​1​, implies it has the effect of reducing n​th​ harmonic 
EMF, where q=slots per pole per phase. 
3. What is the coil span for a 2 pole 18 slot machine? 
a) 9 
b) 4.5 
c) 18 
d) 6 
View Answer 
Answer: a 
Explanation: Coil span= number of slots/number of poles= 18/2=9. 
4. In a machine with coil span 9, if a coil has its one coil-side in slot 1, then its other coil-side 
must be in ____________ 
a) slot 9 
b) slot 8 
c) slot 10