DC Machines
This is a short quiz on DC machines fundamentals
- 1.Winding used for low voltage high current
- A.
Lap winding
- B.
Wave Winding
- C.
Gram ring winding
- D.
Open winding
- 2.No. of parallel paths in lap winding=_________
- A.
Number of poles
- B.
2
- C.
4
- D.
6
- 3.In long shunt compound generator Ise = ____________
- A.
Ia-Ish
- B.
IL
- C.
Ia
- D.
Ia+Ish
- 4.Generated emf is __________ speed of prime mover
- A.
Directly proportional to
- B.
Inversely proportional to
- C.
Equal to
- D.
Less than
- 5.For a 4 pole lap wound DC generator with 32 armature slots, average pitch is
- A.
2
- B.
4
- C.
8
- D.
16
- 6.________ compound generator is used for arc welding
- A.
Long shunt
- B.
Short shunt
- C.
Differential
- D.
Commulative
- 7.% efficiency = ___________
- A.
(Po/Pi)x100
- B.
(Po/Po+Losses)x100
- C.
Both a & b
- D.
None of above
- 8.If VN > VL , Voltage regulation is _________
- A.
Negative
- B.
Positive
- C.
Zero
- D.
1
- 9.Power P (in watts) = __________
- A.
BHPx746
- B.
BHP/746
- C.
BHPx764
- D.
BHP/764
- 10.Series generators are used for
- A.
Series arc lighting
- B.
Voltage booster
- C.
Regenerative breaking
- D.
All of above
- 11.A 110V, 1000 rpm generator will generate ____ V at 1100 rpm
- A.
220
- B.
200
- C.
150
- D.
120
- 12.Cu-Losses are also known as
- A.
I2R
- B.
IR2
- C.
V2/R
- D.
VI
- 13._________ field winding has small number of turns of thick copper wire.
- A.
Shunt
- B.
Series
- C.
Compund
- D.
Separately excited
- 14.Carbon brushes are preferred on copper brushes because of
- A.
Armature reaction
- B.
Reduced reactance voltage
- C.
Hardness of material
- D.
Low resistance
- 15.In Fleming's right-hand rule, the thumb point towards
- A.
Direction of flux
- B.
Direction of induced e.m.f.
- C.
Direction of motion of conductor
- D.
Any of above
- 16.The output voltage of a simple d.c. generator is
- A.
A.c. square wave.
- B.
A.c. sinusoidal wave
- C.
Pure d.c
- D.
Pulsating d.c
- 17.When tow generators are running in parallel and field of one of them is weakened too much then it will
- A.
Deliver large share of the total load
- B.
Deliver small share of the total load
- C.
Run in the opposite direction
- D.
Run as a motor in the same direction
- 18.In shunt generator interpole winding carries ____ current
- A.
Armature
- B.
Shunt field
- C.
Full load
- D.
None of these
- 19.Due to which of the following reasons a separately excited generator is better
- A.
Low price
- B.
Exciting current is independent of load current
- C.
Low armature resistance
- D.
All of above
- 20.Why is the armature of a d.c. machine made of silicon steel
- A.
To reduce eddy current loss
- B.
To reduce hysteresis loss
- C.
Ease of creating slots
- D.
To achieve high permeability
- 21.compound generator is said to be flat compounded if VFL
- A.
> VNL
- B.
< VNL
- C.
= VNL
- D.
= 2VNL
- 22.The commutator segments of a d.c. machine are made of
- A.
Carbon
- B.
Copper
- C.
Mica
- D.
Ceramic
- 23.If the number of poles in a lap wound generator be doubled, then the generated e.m.f .will
- A.
Become half
- B.
Become double
- C.
Increase to four times
- D.
Remain constant
- 24.Which of the following d.c. generator can build up without any residual magnetism
- A.
Compound generator
- B.
Self-excited generator
- C.
Series generator
- D.
Shunt generator
- 25.The efficiency of a d.c. machine is maxiinum when
- A.
Variable losses = constant losses
- B.
Stray losses are = copper losses
- C.
Field copper losses = armature copper losses
- D.
Magnetic losses - windage loss.
Questions: 8 | Attempts: 145758 | Last updated: Apr 30, 2021
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