Electrical Machine Design — MCQs – EE

1. The main objective of electrical machine design is to:
(A) Achieve required performance with minimum cost and maximum efficiency
(B) Increase machine weight
(C) Reduce efficiency for safety
(D) Ignore temperature rise

2. The specific magnetic loading in a machine depends on:
(A) Air-gap flux density
(B) Shaft material
(C) Cooling system
(D) Bearing type

3. The specific electric loading of a machine is defined as:
(A) The total current per meter of armature periphery
(B) The flux per pole
(C) The number of turns per coil
(D) The number of slots per pole

4. The output coefficient of an electrical machine depends on:
(A) Magnetic and electric loadings and machine speed
(B) Stator length only
(C) Temperature rise only
(D) Insulation class

5. The main dimensions of a rotating electrical machine are:
(A) Armature core length and diameter
(B) Shaft diameter and bearing length
(C) Winding size and insulation thickness
(D) Pole pitch and flux density

6. Temperature rise in a machine affects:
(A) Insulation life and efficiency
(B) Shaft strength
(C) Mechanical vibrations only
(D) Power factor

7. The magnetic circuit of an electrical machine consists of:
(A) Stator and rotor cores
(B) Windings only
(C) Bearings and shaft
(D) Frame and enclosure

8. The electrical circuit of a machine mainly includes:
(A) Armature and field windings
(B) Shaft and bearings
(C) Yoke and frame
(D) Cooling ducts

9. The choice of material in machine design affects:
(A) Efficiency, cost, and performance
(B) Color of machine
(C) Power factor only
(D) Maintenance schedule

10. The core loss in magnetic materials consists of:
(A) Hysteresis and eddy current losses
(B) Friction and windage losses
(C) Stray load losses only
(D) Copper losses

11. Copper losses in a machine depend primarily on:
(A) Current and resistance of windings
(B) Flux per pole
(C) Core material
(D) Air-gap length

12. In electrical machine design, insulation class determines:
(A) Maximum permissible temperature rise
(B) Mechanical strength
(C) Power factor
(D) Frequency range

13. Cooling methods in electrical machines are adopted to:
(A) Remove heat and maintain temperature within limits
(B) Increase power loss
(C) Reduce efficiency
(D) Increase weight

14. Ventilation in rotating machines is important because:
(A) It helps dissipate heat generated in cores and windings
(B) It increases magnetic flux
(C) It reduces air-gap
(D) It improves insulation resistance

15. Slot space factor is defined as:
(A) Ratio of copper area to total slot area
(B) Ratio of air-gap flux to pole flux
(C) Ratio of slot pitch to tooth width
(D) Ratio of pole pitch to core length

16. Overheating in electrical machines may be caused by:
(A) Overload and poor ventilation
(B) Low ambient temperature
(C) Reduced current
(D) High insulation resistance

17. Efficiency of electrical machines can be improved by:
(A) Reducing iron and copper losses
(B) Increasing core length
(C) Using more insulation
(D) Increasing air-gap length

18. Frame design of electrical machines should ensure:
(A) Mechanical strength and proper ventilation
(B) Magnetic shielding only
(C) Decorative appearance
(D) Electrical insulation

19. In electrical machine design, air-gap length affects:
(A) Power factor and magnetizing current
(B) Shaft alignment
(C) Insulation thickness
(D) Terminal voltage

20. The choice of number of poles in a machine determines:
(A) Speed and frequency relationship
(B) Size of commutator
(C) Type of insulation
(D) Armature resistance

21. Commutation is a design consideration in:
(A) DC machines
(B) Synchronous motors only
(C) Induction motors only
(D) Transformers

22. Tooth flux density in machine design should be:
(A) Limited to avoid saturation and noise
(B) Increased indefinitely for higher torque
(C) Ignored in design
(D) Kept constant for all machines

23. The armature winding design affects:
(A) Voltage, current, and efficiency of the machine
(B) Shaft speed only
(C) Mechanical losses only
(D) Air-gap temperature

24. The power factor of a machine is improved by:
(A) Reducing magnetizing current
(B) Increasing air-gap
(C) Reducing efficiency
(D) Increasing flux leakage

25. Losses in electrical machines can be categorized as:
(A) Core, copper, mechanical, and stray losses
(B) Insulation and vibration losses only
(C) Cooling and leakage losses only
(D) Conduction and radiation losses

26. The design of windings must ensure:
(A) Electrical, mechanical, and thermal reliability
(B) Minimum conductor usage only
(C) Maximum heat generation
(D) Irregular flux distribution

27. The main constraints in machine design are:
(A) Temperature rise, efficiency, and cost
(B) Speed and shaft size only
(C) Color and paint type
(D) Mounting arrangement only

28. Magnetic saturation in the core should be avoided because it:
(A) Increases magnetizing current and losses
(B) Improves voltage regulation
(C) Increases efficiency
(D) Reduces torque pulsations

29. The mechanical design of a machine primarily involves:
(A) Shaft, bearings, and frame construction
(B) Winding resistance
(C) Magnetic field design
(D) Thermal loading

30. The ultimate aim of a good machine design is to:
(A) Meet performance requirements reliably and economically
(B) Maximize material usage
(C) Increase complexity
(D) Reduce efficiency for safety