Tricky Electrical Machine Design Multiple choice Questions and Answers pdf

91.    The weight of copper of both armature and field windings decreases with _____ in number of poles.
(a)     increase
(b)     decrease
(c)    either of the above
(d)    none of the above
Ans: a

92.    In a D.C. machine the number of brush arms is _____ the number of poles.
(a)     less than
(b)     equal to
(c)    greater than
(d)    none of the above
Ans: b

93.    In a D.C. machine the current per brush arm should not be more than
(a)     100 A
(6)     200 A
(e)    300 A
(d)     400 A
Ans: d

94.    In a D.C. machine, the value of peripheral speed should not, normally, exceed
(a)     10 m/s
(b)     20 m/s
(c)     30 m/s
(d)     40 m/s
Ans: c

95.    In D.C. machines the width of the duct is usually
(a)     4 mm
(b)     6 mm
(c)     8 mm
(d)     10 mm
Ans: d

96.    D.C. machines designed with a large value of air gap length have
(a)    worst, ventilation
(b)    poor ventilation
(c)    better ventilation
(d)    none of the above
Ans: c

97.    In D.C. machines, ir order to prevent excessive distortion of field form by the armature reaction, the field mmf must be made
(a)    equal to that of armature mmf
(b)    less in comparison with the arma¬ture mmf
(c)    large in comparison with the arma-ture mmf
(d)    none of the above
Ans: c

98.    In D.C. machines, the ____ in field mmf results in increase in size and cost of machines.
(a)     increase
(b)     decrease
(c)    either of the above
(d)    none of the above
Ans: a

99.    The operation of a D.C. machine with large air gap lengths is comparatively
(a)     quiet
(b)     noisy
(c)     either of the above
(d)     none of the above
Ans: a

100.    Which of the following methods may be adopted to reduce the effects of armature reaction ?
(a)    Increase in length of air gap at pole tips
(b)    Increasing reluctance of pole tips
(c)    Compensating windings
(d)     Interpoles
(e)    All of the above
Ans: e

101.    In D.C. machines the usual limit of slot pitch is
(a)     between 5 to 10 mm
(b)     between 10 to 15 mm
(c)    between 15 to 20 mm
(d)    between 25 to 35 mm
Ans: d

102.    In D.C. machines the number of slots per pole usually lies
(a)     between 2 to 4
(b)     between 6 to 8
(c)    between 9 to 16
(d)    between 20 to 30
Ans: c

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