Question 1

The design of electromagnets is based upon which of the following fundamental equations ?
A)Force equation
B)Magnetic circuit equation
C)Heating equation
D)All of the above

Accepted Answer

The design of electromagnets involves considerations of the force they exert (force equation), the behavior of magnetic fields in materials (magnetic circuit equation), and the heat generated by electric currents (heating equation). All these aspects are crucial for a comprehensive design.

Question 2

When the two coil sides forming a coil are spaced exactly one pole pitch apart they are said to be of
A)short pitch
B)full pitch
C)either of the above
D)none of the above

Accepted Answer

When the two coil sides forming a coil are spaced exactly one pole pitch apart, they are said to be of full pitch. This means the coil spans the entire distance between two magnetic poles, which is considered the ideal or full pitch configuration for maximizing electromagnetic efficiency in machines like motors and generators.

Question 3

are always double layer type.
A)Closed windings
B)Open windings
C)Either of the above
D)None of the above

Accepted Answer

Closed windings are always double layer type because they are designed to have two layers of conductors, which helps in reducing the leakage reactance and improving the performance of the machine.

Question 4

The distance between the starts of two consecutive coils measured in terms of coil sides is called
A)front pitch
B)winding pitch
C)commutator pitch
D)back pitch

Accepted Answer

Winding pitch is the distance between the starts of two consecutive coils measured in terms of coil sides.

Question 5

The winding where dummy coils are used is sometimes called
A)duplex winding
B)triplex winding
C)forced winding
D)none of the above

Accepted Answer

The answer of The winding where dummy coils are used...

Question 6

Dummy coil should not be used in
A)small machines
B)large machines
C)either (a) or (b)
D)none of the above

Accepted Answer

Dummy coils are generally not used in large machines because they are primarily utilized to reduce the effect of armature reaction in smaller machines. In large machines, other methods are more effective for managing armature reaction and ensuring efficient operation.

Question 7

Power transformers have rating
A)equal to 50 kVA
B)equal to 100 kVA
C)above 200 kVA
D)none of the above

Accepted Answer

Power transformers are typically used in transmission networks for stepping up or down the voltage. They are designed for high efficiency and are usually rated above 200 kVA, often going into the MVA range for large power distribution or transmission networks.

Question 8

Power transformers should be designed to have maximum efficiency
A)at one-fourth load
B)at one-half load
C)at or near full load
D)any of the above

Accepted Answer

Power transformers are typically designed to have maximum efficiency at or near full load because this is when they are most often operated, especially in industrial or utility applications where the demand for power is consistent and high.

Question 9

In transformers using hot rolled steel, the cross-section of the yoke is made about _____ greater than that of the core
A)5 percent
B)10 percent
C)15 percent
D)30 percent

Accepted Answer

The answer of In transformers using hot rolled steel, the...

Question 10

Yokes with rectangular cross-section are used for
A)small capacity transformers
B)medium capacity transformers
C)large capacity transformers
D)any of the above

Accepted Answer

The answer of Yokes with rectangular cross-section are used for
A)small...

Question 11

The cold rolled grain oriented steel has ______ permeability in the direction of the grain orientation.
A)minimum
B)maximum
C)nil
D)none of the above

Accepted Answer

Cold rolled grain oriented steel has maximum permeability in the direction of the grain orientation, which is why it is used in transformer cores to enhance their efficiency by reducing the core's magnetic losses.

Question 12

Cylindrical windings using circular conductors, employed in transformers, are
A)single layered
B)double layered
C)multi-layered
D)none of the above

Accepted Answer

Cylindrical windings using circular conductors in transformers are typically multi-layered to accommodate the required number of turns and to manage the distribution of voltage and current effectively.

Question 13

Helical windings are used in
A)distribution transformers
B)power transformers
C)shell type transformers
D)none of the above

Accepted Answer

Helical windings are typically used in power transformers because they are suitable for handling high currents and provide better mechanical strength and cooling.

Question 14

Multi-layer helical windings are commonly used in the transformers as high voltage windings
A)upto 20 kV
B)upto 50 kV
C)upto 80 kV
D)for 110 kV and above

Accepted Answer

Multi-layer helical windings are typically used for transformers designed for high voltage applications, specifically for 110 kV and above, due to their ability to handle high electrical stress and ensure uniform distribution of voltage along the winding.

Question 15

Disc windings are primarily used in
A)short capacity transformers
B)medium capacity transformers
C)high capacity transformers
D)any of the above

Accepted Answer

Disc windings are primarily used in high capacity transformers because they can better handle the high voltage and current levels, and they offer improved distribution of electrical stresses and cooling characteristics suitable for such applications.

Question 16

The heat dissipating capability of transformers of ratings higher than 30 kVA in increased by providing which of the following ?
A)Corrugations
B)Fins
C)Tubes
D)All of the above

Accepted Answer

Transformers with ratings higher than 30 kVA often have increased heat dissipating capabilities through the use of corrugations, fins, and tubes, all of which enhance the surface area for heat exchange and improve cooling efficiency.

Question 17

Transformers with a capacity of upto _____ have a cooling radiator system with natural cooling
A)2 MVA
B)5 MVA
C)7.5 MVA
D)10 MVA

Accepted Answer

The answer of Transformers with a capacity of upto _____...

Question 18

The forced oil and air circulation method is usual one for transformers of capacities
A)upto 5 MVA
B)upto 10 MVA
C)upto 20 MVA
D)30 MVA upwards

Accepted Answer

Forced oil and air circulation is typically used for cooling transformers of higher capacities, specifically for those with capacities of 30 MVA and upwards, to efficiently manage the heat generated.

Question 19

The flash point of transformer oil should be higher than
A)40°C
B)60°C
C)80°C
D)104°C

Accepted Answer

The flash point of transformer oil should be higher than 104°C to ensure safety and prevent the risk of fire under operating conditions.

Question 20

The voltage control in electric supply networks in required on account of which of the following reasons ?
A)Adjustment of voltage at consumers premises within statutory limits
B)Control of active and reactive power
C)Adjustment of short period daily and seasonal voltage variations in accordance with variations of load
D)All of the above

Accepted Answer

Voltage control in electric supply networks is necessary for several reasons, including adjusting voltage at consumers' premises within statutory limits, controlling active and reactive power, and adjusting for short period daily and seasonal voltage variations in accordance with variations of load.

Quiz 3: Transformer Design and Electromagnets

The design of electromagnets is based upon which of the following fundamental equations ?

When the two coil sides forming a coil are spaced exactly one pole pitch apart they are said to be of

are always double layer type.

The distance between the starts of two consecutive coils measured in terms of coil sides is called

The winding where dummy coils are used is sometimes called

Dummy coil should not be used in

Power transformers have rating

Power transformers should be designed to have maximum efficiency

In transformers using hot rolled steel, the cross-section of the yoke is made about _____ greater than that of the core

Yokes with rectangular cross-section are used for

The cold rolled grain oriented steel has ______ permeability in the direction of the grain orientation.

Cylindrical windings using circular conductors, employed in transformers, are

Helical windings are used in

Multi-layer helical windings are commonly used in the transformers as high voltage windings

Disc windings are primarily used in

The heat dissipating capability of transformers of ratings higher than 30 kVA in increased by providing which of the following ?

Transformers with a capacity of upto _____ have a cooling radiator system with natural cooling

The forced oil and air circulation method is usual one for transformers of capacities

The flash point of transformer oil should be higher than

The voltage control in electric supply networks in required on account of which of the following reasons ?