Question 1

The high voltage winding is usually which of the following type ?
A)Cylindrical winding with circular conductors
B)Cross-over winding with either circular or small rectangular conductors
C)Continuous disc type winding with rectangular conductors
D)All of the above types

Accepted Answer

High voltage windings can be of various types including cylindrical winding with circular conductors, cross-over winding with either circular or small rectangular conductors, and continuous disc type winding with rectangular conductors, depending on the design and application requirements.

Question 2

Which of the following is the basic consideration in the design of insulation ?
A)Electrical considerations
B)Mechanical considerations
C)Thermal considerations
D)All of the above

Accepted Answer

The design of insulation must take into account electrical, mechanical, and thermal considerations to ensure safety, durability, and efficiency.

Question 3

A practical formula for determining the thickness of insulation between low voltage and high voltage windings is
A)1 + 0.2 kVmm
B)2 + 0.5 kVmm
C)4 + 0.7 kV mm
D)5 + 0.9 kV mm

Accepted Answer

D

Question 4

The insulation between windings and grounded core and the insulation between the windings of the same phase is called
A)minor insulation
B)major insulation
C)either of the above
D)none of the above

Accepted Answer

Major insulation refers to the insulation between windings and the grounded core, as well as between the windings of the same phase, ensuring electrical separation and safety.

Question 5

The cylindrical windings using circular conductors are used for current rating of
A)upto 20 A
B)upto 40 A
C)upto 60 A
D)upto 80 A

Accepted Answer

The answer of The cylindrical windings using circular conductors are...

Question 6

The surge phenomenon is particularly important in case of
A)low voltage transformers
B)medium voltage transformers
C)high voltage transformers
D)any of the above

Accepted Answer

The surge phenomenon is particularly important in high voltage transformers because they are more susceptible to overvoltages and require careful design to handle such conditions safely.

Question 7

Which of the following in an application of D.C. motors?
A)Traction
B)Drives for process industry
C)Battery driven vehicles
D)All of the above

Accepted Answer

D.C. motors are used in traction, drives for process industries, and battery-driven vehicles due to their good speed control and high starting torque.

Question 8

D.C. servomotors are used in
A)purely D.C. control systems
B)purely AC. control systems
C)both D.C. and AC. control systems
D)none of the above

Accepted Answer

D.C. servomotors are used in purely D.C. control systems because they are designed to operate on direct current (DC) power.

Question 9

The stator of a D.C. machine comprises of
A)main poles
B)interpoles
C)frame
D)all of the above

Accepted Answer

The stator of a DC machine includes main poles, interpoles, and the frame, making all of the options correct. These components are essential for creating the magnetic field and supporting the structure of the machine.

Question 10

The laminations of the armature of a D.C. machine are usually _____ thick.
A)0.1 to 0.2 mm
B)0.2 to 0.3 mm
C)0.3 to 0.4 mm
D)0.4 to 0.5 mm

Accepted Answer

The answer of The laminations of the armature of a...

Question 11

is usually used for brush rockers
A)Mild steel
B)Copper
C)Aluminium
D)Cast-iron

Accepted Answer

Cast-iron is commonly used for brush rockers due to its good wear resistance and ability to dampen vibrations, making it suitable for the mechanical stresses involved.

Question 12

______ brushes are fragile and cause excessive wear of commutator,
A)Natural graphite
B)Hard carbon
C)Electro graphitic
D)Metal graphite

Accepted Answer

Natural graphite brushes are fragile and cause excessive wear of commutator.

Question 13

Which of the following brushes can be used for high values of current density ?
A)Metal graphite brushes
B)Hard carbon brushes
C)Electro-graphitic brushes
D)Natural graphite brushes

Accepted Answer

Metal graphite brushes are suitable for high current densities due to their low contact resistance and good conductivity.

Question 14

________ is the common method of applying brushes to the commntator.
A)Radial
B)Trailing
C)Reaction
D)All of the above

Accepted Answer

The common method of applying brushes to the commutator in electrical machines involves all the mentioned methods: Radial, Trailing, and Reaction, depending on the specific application and design of the machine.

Question 15

Which of the following problem arises in D.C. motors which are fed from thyristor bridge circuits ?
A)Increased I R losses
B)Increased core losses
C)Poor commutation
D)All of the above

Accepted Answer

When DC motors are fed from thyristor bridge circuits, all of the listed problems can arise. Increased IR losses occur due to higher currents, increased core losses are due to distorted waveforms, and poor commutation is a result of non-linear current flow and fluctuations in the power supply.

Question 16

The weight of copper of both armature and field windings decreases with _____ in number of poles.
A)increase
B)decrease
C)either of the above
D)none of the above

Accepted Answer

The weight of copper in both armature and field windings decreases with an increase in the number of poles because more poles mean shorter mean turn length for the windings, which reduces the amount of copper needed.

Question 17

In a D.C. machine the number of brush arms is _____ the number of poles.
A)less than
B)equal to
C)greater than
D)none of the above

Accepted Answer

In a D.C. machine, the number of brush arms is equal to the number of poles. This is because each pair of poles requires a set of brushes to collect or distribute the current.

Question 18

In a D.C. machine the current per brush arm should not be more than
A)100 A
B)200 A
C)300 A
D)400 A

Accepted Answer

The answer of In a D.C. machine the current per...

Question 19

In a D.C. machine, the value of peripheral speed should not, normally, exceed
A)10 m/s
B)20 m/s
C)30 m/s
D)40 m/s

Accepted Answer

The peripheral speed of a D.C. machine is typically limited to around 30 m/s to ensure mechanical safety and avoid excessive centrifugal forces on the rotating components.

Question 20

In D.C. machines the width of the duct is usually
A)4 mm
B)6 mm
C)8 mm
D)10 mm

Accepted Answer

The width of the duct in D.C. machines is typically around 10 mm to allow for adequate ventilation and cooling.

Quiz 4: Design and Operation of DC Machines

The high voltage winding is usually which of the following type ?

Which of the following is the basic consideration in the design of insulation ?

A practical formula for determining the thickness of insulation between low voltage and high voltage windings is

The insulation between windings and grounded core and the insulation between the windings of the same phase is called

The cylindrical windings using circular conductors are used for current rating of

The surge phenomenon is particularly important in case of

Which of the following in an application of D.C. motors?

D.C. servomotors are used in

The stator of a D.C. machine comprises of

The laminations of the armature of a D.C. machine are usually _____ thick.

is usually used for brush rockers

______ brushes are fragile and cause excessive wear of commutator,

Which of the following brushes can be used for high values of current density ?

________ is the common method of applying brushes to the commntator.

Which of the following problem arises in D.C. motors which are fed from thyristor bridge circuits ?

The weight of copper of both armature and field windings decreases with _____ in number of poles.

In a D.C. machine the number of brush arms is _____ the number of poles.

In a D.C. machine the current per brush arm should not be more than

In a D.C. machine, the value of peripheral speed should not, normally, exceed

In D.C. machines the width of the duct is usually