問題一覧
1
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.
2
.
cumulative compounded generator
3
The seperately excited generators are less expensive than self-excited generators.
False
4
Whenever generators are in parallel their +ve and -ve terminals are connected to the -ve and +ve sides of the bus-bars respectively
false
5
which of the following is the type of drum armature winding
wave winding
6
.
b
7
Which of the following is the correct advantage of carbon brushes
They lubricate and polish the commutator as it rotates
8
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
9
.
improve but terminal voltage will fall
10
.
-1000rpm
11
.
69.3
12
.
cross-magnetising
13
Which of the following is closest to the armature circuit resistance of a dc generator?
1 ohm
14
The commutator of a DC generator acts as _______.
rectifier
15
For parallel operation, the generators normally preferred are
Shunt generators
16
.
c
17
.
in the direction of rotation for the generator and against the direction of rotation for the motor
18
.
40V
19
Select the remedies for neutalising armature reaction
All of the above
20
.
External characteristics
21
.
Eg - V / Ra
22
.
384V
23
.
a
24
.
2,3,4,1
25
.
a
26
.
very small, say about 2 or 3 V
27
What is the internal or toal characteristic of DC Generator
E/Ia
28
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
29
.
b
30
.
partly demagnetizing and partly cross-magnetizing
31
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
32
carbon brushes haven't _____ contact resistance
low
33
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
34
cross magnetising ampere-turns/pole
=ZI(1/2p - θm/360)
35
.
E, P/4
36
.
curve B
37
Which of the following is not the function of the interpoles in dc generators?
Cool armature by ventilating air
38
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
39
Equalizer rights are required in a lap winding dc machine
To prevent the flow of circulating current through the brushes
40
.
50Hz
41
.
c - 1 and 3
42
.
d
43
The core of the armature is made of silicon steel due to
both (B) and (C)
44
.
478.3rpm
45
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%
46
In DC machine, shape of main field flux distribution is
trapezoidal
47
Select the correct e.m.f. equation
Eg =( p φ ZN)/ (60a)
48
Compound generators are used to supply power to : select multiple
railway circuits, motors of electrified steam rail-roads, incandescent lamps
49
.
1066rpm
50
In a DC machine, commutator perform(s) which of the following functions?
Both conversion of AC into DC and vice versa