101. Wave winding is composed of
(a) any
even number of conductors
(b) any
odd number of conductors
(c) that
even number which is exact multiple of poles + 2
(d) that
even number which is exact multiple of poles
Ans: c
102. The critical resistance of the D.C. generator is the
resistance of
(a) field
(b) brushes
(c) armature
(d) loadAns:
a
103. When two D.C. series generators are running in
parallel, an equilizer bar is used (a) to increase the speed and hence
generated e.m.f.
(b) to
increase the series flux
(c) so
that two similar machines will pass approximately equal currents to the load
(d) to reduce the combined effect of ar-mature reaction of both machines
Ans: c
104. Which of the following generating machine will offer
constant voltage on all loads ?
(a) Self-excited generator (b) Separately excited
generator
(c) Level
compounded generator .
(d) All
of the above
Ans: c
105. Which of the following generators will be preferred if
they are required to be run in parallel ?
(a) Shunt
generators
(b) Series
generators
(c) Compound
generators
(d) None
of the above
Ans: a
106. Two generators are running in parallel. One of the
generators may run as motor for which of the following reasons ?
(a) The
direction of that generator is reversed
(b) The
speed of that generator is increased
(c) The
field of that generator is weakened
(d) That
generator takes large share of loads
Ans: d
107. A D.C. generator works on the principle of
(a)
Lenz's law
(b)
Ohm's law
(c)
Faraday's law of electromagnetic induction
(d)
none of the above
Ans: c
108. A series generator can self-excite
(a) only
if the load current is zero
(b) only
if the load current is not zero
(c) irrespective
of the value of load current
(d) none
of the above
Ans: b
109. A shunt generator can self-excite
(a) only
if the resistance of the field circuit is less than critical value
(b)only if the resistance of the field circuit is greater
than critical value
(c) irrespective of the value of the resis-tance in the
field circuit
Ans: a
110. The terminal voltage of a series generator is 150 V
when the load current is 5 A. If the load current is increased to 10 A, the
terminal voltage will be
(a) 150
V
(b) less
than 150 V
(c) greater
than 150 V
(d) none
of the above
Ans: c
111. The open circuit voltage of a compound generator is
250 V. At full load the terminal voltage
(a) will
be less than 250 V
(b) will
always be 250 V
(c) may
be greater or less than 250 V
(d) none
of the above
Ans: c
112. Two D.C. shunt generators, each with armature
resistance of 0.02 ohm and field resistance of 50 ohm run in parallel and
supply a total current of 1000 amperes to the load circuit. If their e.m.fs.
are 270 V and 265 V, their bus bar voltage will be
(a) 270
V
(b) 267.5
V
(c) 265
V
(d) 257.4
V
Ans: b
113. The essential condition for parallel operation of two
D.C. generators is that they have
'
(a)
same kW rating
(b)
the same operation r.p.m.
(c)
the same drooping voltage charac-teristics
(d)
same percentage regulation
Ans: c
114. When two D.C. generators are running in parallel
an equilizer bar is used (a) to increase the series flux
(b) to
increase the generated e.m.f.
(c) to
reduce the combined effect of ar-mature reaction of both the machines
(d) so
that the two identical machines will pass approximately equal currents to the
loadAns: d
115. With a D.C. generator which of the following
regulation is preferred ?
(a)100% regulation
(b)
infinite regulation
(c)
50% regulation
(d)
1% regulation
Ans: d
116. Which generator would you prefer for feeding long D.C.
transmission lines ?
(a) Series
generator
(b) Shunt
generator
(c) Over
compound generator
(d) Flat
compound generator
Ans: c
117. In a D.C. generator the critical resistance can be
increased by
(a) increasing
its field resistance
(b) decreasing
its field resistance
(c) increasing
its speed
(d) decreasing
its speed
Ans: c
118. The number of armature parallel paths in a two-pole
D.C. generator having duplex lap winding is
(a) 2
(b) 4
(c) 6
(d) 8
Ans: b
119. For both lap and wave windings, there are as many
commutator bars as the number of
(a) slots
(b) armature
conductors
(c) winding
elements
(d) poles
Ans: c
120. The series field of a short-shunt D.C. generator is
excited by
(a) external
current
(b) armature
current
(c) shunt
current
(d) load
currentAns: d
121. As a result of armature reaction, the reduction in the
total mutual air gap flux in a D.C.
generator is approximately
(a) 40 percent
(a) 25
percent
(b) 10
percent
(c) 5
percent
Ans: d
122. Shunt generators are most suited for stable parallel
operation because of their
(a)
rising voltage characteristics
(b)
identical voltage characteristics
(c)
drooping voltage characteristics
(d)
linear voltage characteristics
Ans: c
123. The main factor which leads to unstable parallel
operation of flat and over compounded generators is
(a) their
rising voltage characteristics
(b) unequal
number of turns in their series field windings
(c) unequal
speed regulation of their primemovers
(d) unequal
series field resistances
Ans: a
124. If a self excited D.C. generator after being
installed, fails to build up on its first trial run, the first thing to do is
to (a) reverse the field connections
(b) increase
the field resistance
(c) increase
the speed of primemover
(d) check
armature insulation resistance
Ans: a
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