# Design of Electrical Machines Questions and Answers – Modern Trends in Machine Design & Magnetic Leakage

This set of Design of Electrical Machines MCQs focuses on “Modern Trends in Machine Design & Magnetic Leakage”.

1. What are the subjects to which the design of electrical machines is compared to?
a) science and maths
b) maths and art
c) maths
d) science and art

Explanation: The design of electrical machines is basically compared to as a science. It is also compared to as an art because of the designing.

2. How many design problems are present according to the modern trends in design of electrical machines?
a) 2
b) 3
c) 4
d) 5

Explanation: There are 3 design problems involved in the modern trends in the design. They are electromagnetic design, mechanical design and thermal design.

3. What is one of the major aspects in the modern day design?
a) design machines to form a group
b) design machines to provided integrated systems
c) design machines to provide a single system
d) design machine to form multiple group with interconnection

Explanation: The major aspect of the modern trends is that the design of machines should be many in number. At the same time, all the machines should form a part of a single system.

4. How are the machines sometimes designed with respect to ratings?
a) design 2 machines with different rating
b) design a series of machines with different ratings to fit into a single frame size
c) design a series of machines with same rating to fit into a single frame size
d) design 2 machines with the same rating

Explanation: The machines are sometimes being designed as a series of machines with different ratings. They are done so to fit into a single frame size.

5. What are the factors which are considered when the optimal solution involves iterations wherein the values of variables are changed?
a) performance
b) cost constraint
c) performance or cost constraint
d) performance and cost constraint

Explanation: The optimal solution involves iteration wherein the values of variables are changed. This is done to satisfy both the performance and cost constraints.
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6. The computer aided design is one of the modern techniques which is used to provide accurate and comprehensive design.
a) true
b) false

Explanation: The computer aided design is one of the most modern techniques of designing various machines. It is very easy, accurate, easily changeable and a comprehensive design procedure.

7. What is the relation between reluctance, flux and mmf of the machine?
a) low reluctance, less flux leakage, high mmf
b) low reluctance, high flux leakage, high mmf
c) high reluctance, high flux leakage, low mmf
d) high reluctance, less flux linkage, high mmf

Explanation: The designer’s problem is to provide a path of low reluctance to that of comparatively little flux leaks away. In order to compensate for the flux leakage, high mmf is maintained.

8. How should the air gaps be present in the magnetic circuit according to length and cross section?
a) low length, low cross section
b) high length, high cross section
c) high length, low cross section
d) low length, high cross section

Explanation: The air gaps should be present in the magnetic circuit in the low length. The air gap should have maximum cross section to reduce the reluctance.

9. What is the function of the leakage flux?
a) contributes to the transfer of energy
b) contributes to the conversion of energy
c) contributes to both the conversion of energy and transfer of energy
d) does not contributes to the conversion or transfer of energy

Explanation: The leakage flux produced due to the low reluctance path does not transfer the energy produced. The leakage flux also does not convert the energy in the system.

10. How many factors does the leakage flux affect?
a) 6
b) 7
c) 8
d) 9

Explanation: There are 8 factors which are affected by the leakage flux. They are performance of rotating machines and transformers, excitation demands of salient pole machines, leakage reactance of windings, forces between windings, voltage regulation of ac generator and transformers, commutation condition in dc machines, stray load losses, circulating current in transformer tank walls.

11. In the B-H magnetization curve, the flux density occupies the x axis.
a) true
b) false

Explanation: In B-H curve, the flux density occupies the y axis always. In the magnetization curve, magnetic field intensity is plotted.

12. What is the formula of the leakage coefficient?
a) leakage coefficient = total flux * useful flux
b) leakage coefficient = total flux / useful flux
c) leakage coefficient = useful flux / total flux
d) leakage coefficient = total flux + useful flux

Explanation: The total flux is the addition of the useful flux and the leakage flux is first calculated. On substitution the leakage coefficient can be obtained.

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