Electrical Machine Design MCQ (Multiple Choice Questions)

Here are 1000 MCQs on Electrical Machine Design (chapterwise).

1. Which of the following circuit is designed to dissipate heat produced in the machine?
a) Electric circuit
b) Magnetic circuit
c) Dielectric circuit
d) Thermal circuit
View Answer

Answer: d
Explanation: A thermal circuit in electrical machine design deals with the mode and media to dissipate heat produced in the machine. The heat produced in the machine leads to losses.

2. Which of the following materials is generally used in the design of electromagnetic machines?
a) Paramagnetic materials
b) Diamagnetic materials
c) Ferromagnetic materials
d) Core-magnetic materials
View Answer

Answer: c
Explanation: Ferromagnetic materials can strongly act like a magnet when placed in a magnetic field. They are exhibited by materials such as iron, cobalt, nickel, etc. Ferromagnetic materials are generally used in electromagnetic machines.

3. What must be mainly ensured to keep the temperature rise within limits?
a) Good efficiency of the machine
b) Proper cooling and ventilation
c) Proper saturation level
d) Good insulation
View Answer

Answer: b
Explanation: Temperature rise will affect the life of the insulation. Thus, proper cooling and ventilation must be ensured according to electric machine design to keep the temperature rise within limits. The coolant flowing will absorb the heat from machine parts.

4. Which of the following kind of conductors will require thicker insulation?
a) Large sized conductor
b) Small-sized conductor
c) Conductors with high permeance
d) Conductors with low permeance
View Answer

Answer: a
Explanation: Maximum voltage stress and mechanical stress is necessary to determine the size of insulation. Thus, if two electrical machines operate at the same voltage, large-sized conductors will need thicker insulation.

5. Which of the following factor mainly determines the type of insulation for an electrical machine?
a) Maximum allowable flux density
b) Maximum operating temperature
c) Maximum efficiency of the machine
d) Maximum allowable loss in machine
View Answer

Answer: b
Explanation: Temperature rise affects the life of the insulation which can further reduce the operating life of the machine. Thus, maximum operating temperature determines the type of insulation for an electrical machine.
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6. How should be the magnetic and electrical loadings in a highly efficient electric machine?
a) It must be small
b) It must be large
c) It must be equal to the current density
d) It must be equal to the flux density
View Answer

Answer: a
Explanation: To reduce operating costs the efficiency of the machine must be made higher. The magnetic and electrical loadings in a highly efficient electric machine must be small and use more material.

7. What kind of emf is produced in an electric machine when the coil is stationary and flux varies with time?
a) Transformer emf
b) Motional emf
c) Interactional emf
d) Induction emf
View Answer

Answer: a
Explanation: Transformer emf also called the pulsational emf is produced when the coil is stationary and flux varies with time. No energy conversion takes place in this process. This kind of emf is generated in a transformer.

8. What kind of materials are used to design electrical heating devices?
a) High Conductivity Materials
b) High Resistivity Materials
c) High Weldability Materials
d) High Solderability Materials
View Answer

Answer: b
Explanation: High resistive materials are used to make resistances or heating devices as we require to dissipate electrical energy as heat. These are generally obtained by using an alloy of different metals.

9. What are the main dimensions of a rotating electric machine?
a) Field diameter and Armature core length
b) Armature diameter and Field core length
c) Armature diameter and Armature core length
d) Field diameter and Field core length
View Answer

Answer: c
Explanation: The armature is the part of the machine that carries AC. The main dimensions in a rotating electric machine are said to be the Armature diameter and Armature core length.

10. What determines the output of a dc electric machine?
a) Only Total Magnetic loading
b) Only Total Electric loading
c) Total loadings
d) Either Total Magnetic loading or Total Electric loading
View Answer

Answer: c
Explanation: The dc electric machine output is the product of Total Magnetic loading, Total Electric loading, and speed in rps. Thus the output depends on total loadings.

11. How will the size and cost of a rotating electric machine be if it is designed with greater speed?
a) small size and more cost
b) small size and less cost
c) large size and more cost
d) large size and less cost
View Answer

Answer: b
Explanation: The rotating electric machine designed with greater speed will have a smaller size and lesser cost compared to other machines giving the same output but designed at lesser speeds. This is because the volume of active parts of the machine varies inversely with speed.

12. What is the relation between the output coefficient to the volume of active parts in a rotating electric machine?
a) directly proportional
b) inversely proportional
c) equal to
d) No relation can be established
View Answer

Answer: b
Explanation: The output coefficient and the volume of active parts in a rotating electric is inversely proportional to each other. Thus, the size of the machine decreases with an increase in output coefficient.

13. How should be the output coefficient of a rotating electric machine from an economics point of view?
a) High
b Low
c) Moderate
d) Output coefficient does not affect the economics
View Answer

Answer: a
Explanation: The rotating electric machine designed with a higher output coefficient will have a smaller size and lesser cost. This volume of active parts of the machine varies inversely with the output coefficient. Thus, the output coefficient of a rotating electric machine must be high.

14. How should be the specific loadings to design a machine with reduced dimensions?
a) Increased values of specific loadings
b) Decreased values of specific loadings
c) Zero specific loadings
d) Moderate values of specific loadings
View Answer

Answer: a
Explanation: The output coefficient is proportional to the product of specific magnetic loading and specific electric loading. The output coefficient of a rotating electric machine is inversely proportional to the output coefficient. Thus, increased values of specific loadings will give a small size machine.
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15. Where does maximum flux density occur in a well-designed electric machine?
a) In the rotor
b) In the air gap
c) In the teeth
d) In the poles
View Answer

Answer: c
Explanation: The maximum flux density in a well-designed electric machine occurs in the teeth of the machine. The flux density in teeth is directly proportional to the specific magnetic loading.

16. Which of these factors does not determine the specific magnetic loading in rotating machines?
a) Magnetizing current
b) Core loss
c) Maximum flux density in iron parts
d) Number of parallel paths
View Answer

Answer: d
Explanation: The Magnetizing current, Core loss, and Maximum flux density in iron parts of the machine are the factors that help in determining the specific magnetic loading in rotating machines.

17. What is the other name for a short-pitched coil electrical machine?
a) Coiled
b) Commutated
c) Winded
d) Chorded
View Answer

Answer: d
Explanation: Two coil sides can form a full pitched coil when they are spaced one pole pitch apart. A coil span less than a pole pitch is called a short-pitched coil or chord.

18. What kind of layer winding does a closed winding of an electric machine usually have?
a) Single layer
b) Double layer
c) Single layer or Double layer
d) Mixture of single layer and double layer
View Answer

Answer: b
Explanation: A double layer winding has identical coils where one coil side of each coil lies in the top half portion of slot and another side on the bottom half of another slot. Such a winding is used to make closed winding.

19. Why are tapered interpoles used in large DC electric machines?
a) To eliminate saturation at root of pole
b) To obtain higher speeds
c) To obtain maximum torque
d) To eliminate eddy current loss
View Answer

Answer: a
Explanation: At heavy overloads saturation at the root of the pole may occur. Thus, tapered interpoles are used to eliminate saturation at root of the pole.
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20. Which part of an electric machine is designed to give the main magnetic flux?
a) Interpoles
b) Frame
c) Main poles
d) Commutator
View Answer

Answer: c
Explanation: Main poles is the part of an electric machine that is designed to give the main magnetic flux. This is present in the field system of the dc machine which is responsible to produce magnetic flux for the necessary excitation.

21. Which of the following is used to connect the armature conductors to the commutator?
a) vee-ring
b) Equalizer ring
c) Banding
d) Risers
View Answer

Answer: c
Explanation: A commutator helps in rectifying the alternating current that is induced in armature. A riser is used to connect the armature conductors to the commutator. Riser segments are made of copper strips in a large machine.

22. What process takes place in an electric machine when stationary is kept in a time-varying field?
a) Energy conversion
b) Energy transference
c) Rotation of coil
d) Movement of coil
View Answer

Answer: b
Explanation: Transformer emf is produced when the coil is stationary and flux varies with time. No energy conversion takes place in this process thus, only energy transference takes place. This kind of emf is generated in the transformer.

23. Which of the following is the same as the transformer emf?
a) Pulsational emf
b) Induction emf
c) Interactional emf
d) Motional emf
View Answer

Answer: a
Explanation: Pulsational emf is also called the transformer emf. It is produced when the coil is stationary and flux varies with time. Such emf is produced in a transformer and no motion takes place in this machine.

24. How will be the size and cost of a rotating electric machine that has a higher output coefficient be?
a) small size and more cost
b) small size and less cost
c) large size and more cost
d) large size and less cost
View Answer

Answer: b
Explanation: The rotating electric machine designed with a higher output coefficient will have a smaller size and lesser cost compared to other machines having a lower output coefficient. This is because the volume of active parts of the machine varies inversely with the output coefficient.

25. How will high specific loading according to rotating electric machine affect the efficiency?
a) Efficiency increases
b) Efficiency decreases
c) Efficiency may increase or decrease
d) Efficiency is not affected
View Answer

Answer: b
Explanation: Higher the specific loading, lower will be the size and cost of the machine but the efficiency, power factor, commutation conditions in dc machines are affected. Thus, a suitable value of specific loadings needs to be selected.

26. What kind of layer winding in an electric machine occupies the whole slot by one coil side of the coil?
a) Single layer
b) Double layer
c) Single layer or Double layer
d) Mixture of single layer and double layer
View Answer

Answer: a
Explanation: A single layer winding occupies the whole slot by one coil side of the coil. Such a winding is used to make open windings but is not used for closed windings.

27. What are the different types of interpoles in DC electric machines?
a) Parallel sided and Tapered
b) Open and closed
c) Single layer and double layer
d) Armature and field
View Answer

Answer: a
Explanation: Interpoles are placed in a machine to improve the commutation conditions. The two types of interpoles are Parallel sided and Tapered where tapered are generally used for large machines.

28. What is the relation between hysteresis and the number of poles?
a) hysteresis loss decreases with an increase in number of poles
b) hysteresis loss increases with an increase in number of poles
c) hysteresis loss remains constant with an increase in number of poles
d) hysteresis loss may increase or decreases with an increase in number of poles
View Answer

Answer: a
Explanation: Keeping the core area the same, the hysteresis loss for a 4 pole machine will be half of that in a 2 pole machine. Thus, hysteresis loss decreases with an increase in the number of poles.

29. Which of these will increase with an increase in the number of poles?
a) Weight of field copper
b Number of commutator segments
c) Overall diameter of machine
d) Weight of armature copper
View Answer

Answer: b
Explanation: The weight of field copper, armature copper, and the overall diameter of the machine decreases with an increase in the number of poles. The number of commutator segments will increase with an increase in the number of poles.

30. How should be the value of field mmf to prevent excessive distortion of field form by armature reaction in an electric machine?
a) large compared to armature mmf
b) small compared to armature mmf
c) zero
d) large or small compared to armature mmf
View Answer

Answer: a
Explanation: The field mmf must be large compared to armature mmf to prevent excessive distortion of field form by armature reaction. The air gap length can be made large to reduce the distortion effect of armature reaction as a long air gap needs a large field mmf.

31. Which of these windings are said to be bifurcated windings?
a) Whole coil winding
b) Semi-closed winding
c) half-coil winding
d) Hemitropic windings
View Answer

Answer: a
Explanation: In electric machine design whole coil windings are also called bifurcated windings. In such a winding, it can be seen that the coils that comprise a pair of pole phase group are split into 2 sets of concentric coils.

32. How will the length of the air gap in a DC electric machine affect pulsational loss in pole faces?
a) Pulsational loss increases with an increase in air gap length
b) Pulsational loss decreases with an increase in air gap length
c) Pulsational loss does not change with an increase in air gap length
d) Pulsational loss may increase or decrease with an increase in air gap length
View Answer

Answer: b
Explanation: The change in air gap flux density is small when the length of the air gap is increased. This is due to slotting. The pulsational loss in the pole face decreases with an increase in air gap length.

33. Which of these options are correct for a DC electric machine with a large air gap?
a) More pulsational loss in pole face
b) Quieter operation of the machine
c) Distorting effect of armature reaction more
d) No proper ventilation
View Answer

Answer: b
Explanation: A DC electric machine with a large air gap has less pulsational loss in pole face, quieter operation of the machine, less distorting effect of armature reaction, and improved ventilation.

34. How should be the number of slots in a DC electric machine for better cooling of armature conductors?
a) Large number of slots
b) Less number of slots
c) Slots equal to the number of poles
d) Number of slots depends on commutation
View Answer

Answer: a
Explanation: A large number of slots will require fewer conductors per slot and only fewer conductors are bunched together. For better cooling of armature conductors, a large number of slots are needed.

35. Which of the following circuit is made to insulate one conductor from another?
a) Electric circuit
b) Magnetic circuit
c) Dielectric circuit
d) Thermal circuit
View Answer

Answer: c
Explanation: A dielectric circuit in electrical machine design has insulation that is used to insulate one conductor from another. They are also used to insulate the windings and the core.

36. How is the saturation level of ferromagnetic materials determined in electrical machines?
a) Using maximum allowable flux density
b) Using specific permeance
c) Using the linear velocity of material
d) Using maximum allowable loss
View Answer

Answer: a
Explanation: The maximum allowable flux density helps in determining the saturation level of ferromagnetic materials. More the flux density more will be the excitation.

37. What part of electric machines will the temperature rise mainly affect?
a) Conductance of winding
b) Insulation of machine
c) Speed of machine
d) Torque of machine
View Answer

Answer: b
Explanation: Temperature rise will affect the life of the insulation. If insulation is affected the life of the machine also decreases. Proper cooling and ventilation must be ensured according to electric machine design to keep the temperature rise within limits.

38. How is the size of insulation determined?
a) By maximum voltage stress and maximum saturation
b) By mechanical stress
c) By maximum saturation and mechanical stress
d) By maximum voltage stress and mechanical stress
View Answer

Answer: d
Explanation: Maximum voltage stress and mechanical stress is necessary to determine the size of insulation. In case if two machines operate at the same voltage, large-sized conductors will need thicker insulation.


Chapterwise Multiple Choice Questions on Electrical Machine Design

Design of Electrical Machines MCQ - Multiple Choice Questions and Answers

Our 1000+ MCQs focus on all topics of the Electrical Machine Design subject, covering 100+ topics. This will help you to prepare for exams, contests, online tests, quizzes, viva-voce, interviews, and certifications. You can practice these MCQs chapter by chapter starting from the 1st chapter or you can jump to any chapter of your choice.
  1. Electrical Engineering Materials
  2. Thermal Design Aspects of Electrical Machines & D.C. Machines
  3. Design of Transformers
  4. Three Phase Induction Motor
  5. Design of Synchronous Machines
  6. Design of Permanent Magnet (PM) DC Motors
  7. Design of Electromagnets
  8. Design of Current Transformers (CT)
  9. Aspects of Design of Mechanical Parts
  10. Design of Single Phase Induction Motor
  11. Design of Small Electrical Machines, Starters and Field Regulators
  12. Computer Application in Electrical Machine Design
  13. Fundamental Aspects of Electrical Machine Design
  14. Principles of Magnetic Circuit Design
  15. General Concepts and Constraints in Design of Rotating Machines

1. MCQ on Electrical Engineering Materials

The section contains Design of Electrical Machine multiple choice questions and answers on electrical conducting materials, high conductivity materials, temperature rise, magnetic and insulating materials.

  • Electrical Conducting Materials
  • High Conductivity Materials
  • Magnetic Materials
  • Insulating Materials
  • Temperature Rise and Insulating Materials
  • 2. Multiple Choice Questions on Thermal Design Aspects of Electrical Machines & D.C. Machines

    The section contains Electrical Machine Design questions and answers on machines rating, armature design, commutator and brushes design, dc machines output equation design, poles number selection and pole design.

  • Rating of Machines
  • Design of Armature
  • Design of Commutator and Brushes
  • Design of Output Equations
  • Selection of Number of Poles
  • Pole Design
  • 3. Design of Electrical Machines MCQ on Design of Transformers

    The section contains Design of Electrical Machine MCQs on window space factor, core and winding design, transformers temperature rise, tank design, transformers cooling methods and overall dimensions.

  • Window Space Factor
  • Design of Core and Winding – 1
  • Design of Core and Winding – 2
  • Temperature Rise in Transformers
  • Design of Tank
  • Methods of Cooling of Transformers
  • Overall Dimensions – 1
  • Overall Dimensions – 2
  • 4. Electrical Machines Design Multiple Choice Questions on Three Phase Induction Motor

    The section contains Electrical Machine Design multiple choice questions and answers on three phase induction motor dimensions, rotor bars and slots design, wound rotor design, no load current, dispersion coefficient, stator windings, losses and efficiency.

  • Main Dimensions
  • Design of Rotor Bars and Slots
  • Design of End Rings
  • Design of Wound Rotor
  • No Load Current
  • Dispersion Coefficient
  • Losses and Efficiency
  • Stator Winding
  • 5. Design of Synchronous Machines MCQ

    The section contains Design of Electrical Machine questions and answers on synchronous machines types, hydro generators construction, turbo alternators construction, armature design, field winding design, rotor design, losses and temperature rise, synchronous machines output equation and slot dimensions.

  • Types of Synchronous Machines
  • Construction of Hydro-Generators – 1
  • Construction of Hydro-Generators – 2
  • Construction of Turbo-Alternators
  • Armature Design – 1
  • Armature Design – 2
  • Design of Field Winding – 1
  • Design of Field Winding – 2
  • Design of Rotor – 1
  • Design of Rotor – 2
  • Losses and Temperature Rise
  • Synchronous Machines Output Equation
  • Slot Dimensions
  • 6. Design of Permanent Magnet (PM) DC Motors Multiple Choice Questions

    The section contains Electrical Machine Design MCQs on design preliminaries, design steps and considerations of permanent magnet dc motors.

  • Design Preliminaries
  • Design Steps and Considerations – 1
  • Design Steps and Considerations – 2
  • 7. Design of Electromagnets MCQ

    The section contains Design of Electrical Machine multiple choice questions and answers on electromagnets types, electromagnets construction and magnet coils design.

  • Types of Electromagnets
  • Construction of Electromagnets
  • Design of Magnet Coils
  • 8. Design of Current Transformers (CT) Multiple Choice Questions

    The section contains Electrical Machine Design questions and answers on current transformers errors and construction, design principles and turns compensation.

  • Errors
  • Current Transformers Construction
  • Design Principles
  • Turns Compensation
  • 9. Aspects of Design of Mechanical Parts MCQ

    The section contains Design of Electrical Machine MCQs on shaft design, bearings, ac and dc machines frames, rotor windings bracing and fan design.

  • Design of Shaft
  • Bearings
  • Frames of D.C. & A.C. Machines
  • Bracing of Rotor Windings
  • Design of Fan
  • 10. Design of Single Phase Induction Motor Multiple Choice Questions

    The section contains Electrical Machine Design multiple choice questions and answers on motor types, single phase induction motor construction and output equations, stator and rotor design, single phase induction motor parameters and operating characteristics.

  • Types of Motor
  • Single Phase Induction Motor Construction
  • Output Equation
  • Design of Stator
  • Design of Rotor
  • Parameters
  • Operating Characteristics
  • 11. Multiple Choice Questions on Design of Small Electrical Machines, Starters and Field Regulators

    The section contains Design of Electrical Machine questions and answers on small reluctance motor and small universal commutator designs, motor starters, calculation of resistance steps & field regulators design.

  • Design of a Small Reluctance Motor
  • Design of Small Universal Commutator Motors
  • Motor Starters, Calculation of Resistance Steps & Design of Field Regulators
  • 12. Computer Application in Electrical Machine Design MCQ

    The section contains Electrical Machine Design MCQs on computer aided design, transformers computer aided design, dc motor and synchronous machine designs.

  • Computer Aided Design & Computer Aided Design of Transformers
  • Design of Dc Motor & Synchronous Machine
  • 13. Fundamental Aspects of Electrical Machine Design Multiple Choice Questions

    The section contains Design of Electrical Machine multiple choice questions and answers on machines designs, designs limitations, machine design modern trends and magnetic leakage.

  • Design of Machines, Limitations in Design
  • Modern Trends in Machine Design & Magnetic Leakage
  • 14. Principles of Magnetic Circuit Design MCQ

    The section contains Electrical Machine Design questions and answers on iron losses determination, slot leakage, pulsation losses, leakages types, field form, flux distribution curve harmonic analysis, specific permeance and magnetizing current calculations.

  • Determination of Iron Losses & Slot Leakage
  • Pulsation Losses & Types of Leakages
  • Specific Permeance & Calculation of Magnetizing Current
  • Field Form, Harmonic Analysis of Flux Distribution Curve
  • 15. General Concepts and Constraints in Design of Rotating Machines Multiple Choice Questions

    The section contains Design of Electrical Machine MCQs on relation between rating and dimensions, rotating machines output variation, standard frames, separation of d and l.

  • Relation Between Rating, Dimensions, Variation of Output of Rotating Machines
  • Separation of D and L, Standard Frames
  • If you would like to learn "Design of Electrical Machines" thoroughly, you should attempt to work on the complete set of 1000+ MCQs - multiple choice questions and answers mentioned above. It will immensely help anyone trying to crack an exam or an interview.

    Wish you the best in your endeavor to learn and master Design of Electrical Machines!

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