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問題一覧
1
By looking p at which part of the shunt motor, it can be easily confirmed that a particular motor is DC Motor
Commutator
2
If a speed of a DC shunt motor is increased, the back emf of the motor will
increase
3
As the load is increased the speed of DC shunt motor will
reduced slightly
4
It is a DC motor that tends to over speed when the field opened while running
shunt motor
5
A DC shunt motor is rotating in clockwise direction as viewee from one end. The polarity of connection of the armature and field winding are reversed simultaneously. The motor will
rotate in clockwise direction
6
DC shunt motors are used for driving
machine tools
7
Which of the following statement is correct in case of a DC Series Motor
It should be directly connected to the load
8
If the current in the armature of dc series is reduced to 50% the torque of the motor will become
25% of the previous value
9
Which DC Motor will be preffered for elevators
Cumulative Compound Motor
10
For both lap and wave windings, there are as many commulator bars as the number of
winding elements
11
For a DC Generator when the number of poles and the number of armature conductors is fixed, then which winding will give higher emf?
wave winding
12
Which of the following components of DC generator plays vital role for providing direct current of a DC Generator
Commulator
13
In DC generators, lap winding is used for
low voltage, high current
14
In a DC generator the critical resistance refers to the resistance of
field
15
The number of armature parallel in two pole DC Generator having duplex lap
4
16
The number of armature parallel paths in two pole DC Generator having duplex winding is
4
17
If the armature of an eight-pole dc machine were wound with a simplex wave winding, how many parallel paths would there be?
2 paths
18
The direction of rotation of a dc motor is reversed by
reversing armature connections
19
Which of the following loss in a DC generator varies significantly with the load current?
armature copper loss
20
If Bmax is the maximum flux density, then addy current loss will vary as
(Bmax)2
21
The hysteresis loss in DC generator with the frequency of magnetic reversals as
f
22
In case of DC machines, mechanical losses are primary function of
speed
23
In which of the following application DC series motor is invariably used?
starter for a car
24
A DC series motor, as compared to shunt and compound motors, has the highest torque at the start because if its comparatively
stronger series filed
25
A series motor is best suited for driving
cranes and hoists
26
Which DC motor will be suitable along with flywheel for intermittent light and heavy loads?
cumulatively compounded motor
27
Differentially compound DC motors can find applications requiring
low starting torque
28
In an overload motor main danger arises due to
winding getting overheated
29
No-load speed of which of the following motor will be highest?
series motor
30
A shearing machine has cyclic load consisting of intrpermittent ligth and heavy loads. Which of the following DC motor suitable for this purpose?
cumulative compound motor
31
The ratic of starting torque to full-load torque is least in case of
shunt motor
32
The type of DC motor used for shears and punches is
cumulative compound DC motor.
33
Which DC motor will have keast percentage increase of input current p, for the same percentage increase in the toque
series motor
34
These day DC motor are widely used in
electic traction
35
The direction of rotation of a DC series motor can be changed by
intercharging field terminals
36
If a DC motor is to be selected for conveyors, which motor would be preferred
series motor
37
Which DC motor will be preferred for constant speeed line shafting?
Shunt motor
38
A DC generetor works on the principle of
Faraday’s law of eletromagnetic induction
39
For generating large current on DC generators which winding is generally preferred?
lap winding
40
In case of DC machine winding, number of commutater segment is equal to
number of armature coils
41
The purpose providing dummy coils in a generator is
to provide mechanical balance for the rotor
42
In a DC generator the critical resistance to the resistance of
field
43
In a DC generator in order to reduce sparking at brushes p,the self-induced emf in the coil is neutralized by all of the following except
dummy coil
44
Interpoles are connected _____ with the armature and compensating windings are connecties in _____ with the armature
series, series
45
In a DC machine stray loss is the sum of
Iron loss and mechanical loss
46
Which of the following losses are significantly reduced by laminating the core of a DC generator
Eddy current losses
47
If residual magnetism of a shunt generator is destroyed accidentally, it may be restored by connecting its shunt field
To a battery
48
One dc motor drives another de motor. The second dc motor when excited and driven
Runs as a generator
49
In over compound generato, full load terminal voltage is
More than no-load terminal voltage
50
The series field of a short-shunt DC generator is excited by
load current
51
Whem the shunt field of a compound generator is connected across both series field and armature.suah a connection is known as
Long shunt
52
Drop speed of a DC generator due to increase in load can be compensated by
Increase the input to prime mover
53
Lamination of core are generally made of
silicon steel
54
the field of DC generators are usually made of
copper
55
The bearings used to support the rotor shatfs are geneally
ball bearings
56
Brushes of DC machine are made of
carbon
57
The insulting material used between the comutator segment is normally
mica
58
Welding generator will have
lap winding
59
In case of DC machine winding,number of commutator segmentis equal to
number of armature coils
60
Which one of the following generators is used for charging batteries?
shunt