問題一覧
1
In a DC machine, the armature winding is made up of number of coils distributed in large number of armature slots instead of placing all the coils into two slots to
Make the armature dynamically balanced
2
.
E, P/4
3
.
very small, say about 2 or 3 V
4
.
50Hz
5
.
384V
6
.
a
7
.
cross-magnetising
8
.
improve but terminal voltage will fall
9
.
in the direction of rotation for the generator and against the direction of rotation for the motor
10
.
partly demagnetizing and partly cross-magnetizing
11
.
c - 1 and 3
12
.
Eg - V / Ra
13
.
External characteristics
14
.
69.3
15
.
b
16
.
cumulative compounded generator
17
.
-1000rpm
18
.
478.3rpm
19
.
b
20
.
curve B
21
.
40V
22
.
1066rpm
23
.
d
24
.
a
25
.
2,3,4,1
26
The seperately excited generators are less expensive than self-excited generators.
False
27
Compound generators are used to supply power to : select multiple
railway circuits, motors of electrified steam rail-roads, incandescent lamps
28
Which of the following statement is correct for flat compound generator?
has a load voltage characteristic in which the on-load and full-load voltages are equal
29
What is the internal or toal characteristic of DC Generator
E/Ia
30
Which of the following is the correct advantage of carbon brushes
They lubricate and polish the commutator as it rotates
31
which of the following is the type of drum armature winding
wave winding
32
Select the correct e.m.f. equation
Eg =( p φ ZN)/ (60a)
33
Select the remedies for neutalising armature reaction
All of the above
34
.
c
35
cross magnetising ampere-turns/pole
=ZI(1/2p - θm/360)
36
carbon brushes haven't _____ contact resistance
low
37
Whenever generators are in parallel their +ve and -ve terminals are connected to the -ve and +ve sides of the bus-bars respectively
false
38
2000kW,400 V, 14 poles with 14 parallel paths, Total number of conductors is 1100, the ratio of the pole arc to the pole pitch is 0.7, Calculate the compensating winding conductors per pole so that uniform airgap remains at the pole phase.
4
39
The commutator of a DC generator acts as _______.
rectifier
40
In DC machine, shape of main field flux distribution is
trapezoidal
41
In a DC machine, commutator perform(s) which of the following functions?
Both conversion of AC into DC and vice versa
42
If the no-load voltage of a certain generator is 220 V and the rated load voltage is 200 V, then the voltage regulation is
10%
43
If 0mbe the mechanical degrees, 0ebe the electrical degree and P be the number of poles on a dc generator, then which of the following relations is valid?
0m = 20e/P
44
A 4-pole dynamo with wave would armature has 51 slots containing 20 conductors. The voltage induced is 357 V and the speed is 8500 rpm. The flux per pole will be
1.2 x 10-3 Wb.
45
For parallel operation, the generators normally preferred are
Shunt generators
46
Equalizer rights are required in a lap winding dc machine
To prevent the flow of circulating current through the brushes
47
Which of the following is closest to the armature circuit resistance of a dc generator?
1 ohm
48
A dc shunt generator has full load voltage regulation of 5% at rated speed of 400 rpm. The generator is new driven at 500 rpm. Its voltage regulation now will be
more than 5 percent
49
The core of the armature is made of silicon steel due to
both (B) and (C)
50
Which of the following is not the function of the interpoles in dc generators?
Cool armature by ventilating air