Free Electrical Machines MCQs with Answers
1,061 Electrical Machines MCQs from Electrical Engineering, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
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- A. 50 to 200
- B. 500 to 1000
- C. 1500 to 2500
- D. 3000 to 5000
Explanation: Diesel-electric locomotives commonly fall in the approximate 1,500 to 2,500 horsepower range.
Correct answer: 1500 to 2500- A. electric locomotives
- B. diesel engine locomotives
- C. steam engine locomotives
- D. diesel electric locomotives
- E. all of the above
Explanation: Indian railway traction has historically included steam, diesel, diesel-electric, and electric locomotives.
Correct answer: all of the above- A. up to 1500
- B. 1500 to 2000
- C. 2000 to 3000
- D. 3000 to 4000
Explanation: Steam locomotives generally had lower power ratings than modern diesel or electric locomotives, commonly reaching up to about 1,500…
Correct answer: up to 1500- A. flywheel
- B. gear box
- C. applying brakes 11.
- D. regulating steam flow to engine
Explanation: In a steam locomotive, engine speed and tractive effort are primarily controlled by regulating the steam admitted to the cylinders.
Correct answer: regulating steam flow to engine- A. Electric
- B. Diesel
- C. Steam
Explanation: Electric locomotives usually have the highest operational availability because they have fewer moving parts and do not require onboard…
Correct answer: Electric- A. 5 to 10 percent
- B. 15 to 20 percent
- C. 25 to 35 percent
- D. 35 to 45 percent
Explanation: Steam locomotives lose much energy in the boiler, steam cycle, and mechanical transmission, so their overall efficiency is typically only…
Correct answer: 5 to 10 percent- A. universal motor
- B. single phase induction motor
- C. two phase induction motor
- D. three phase induction motor
Explanation: An AC servomotor is commonly constructed as a two-phase induction motor, with one winding used for excitation and the other for control.
Correct answer: two phase induction motor- A. Constant current
- B. Constant voltage
- C. Constant current as well as constant voltage
- D. Constant current, constant voltage and constant power
- E. None of the above
Explanation: An amplidyne is a high-gain rotating amplifier whose output can be arranged for constant-current, constant-voltage, or constant-power…
Correct answer: Constant current, constant voltage and constant power- A. two phase induction motor
- B. Three phase induction motor
- C. direct current series motor
- D. universal motor
Explanation: An AC servomotor is essentially a specially designed two-phase induction motor with separate reference and control windings.
Correct answer: two phase induction motor- A. minimum
- B. maximum
- C. nil
- D. none of the above
Explanation: Cold-rolled grain-oriented steel is processed so its magnetic domains align readily along the rolling direction.
Correct answer: maximum- A. single layered
- B. double layered
- C. multi-layered
- D. none of the above
Explanation: Cylindrical transformer windings made with circular conductors are built from several turns arranged in successive layers, so they are…
Correct answer: multi-layered- A. upto 20 kV
- B. upto 50 kV
- C. upto 80 kV
- D. for 110 kV and above
Explanation: Multi-layer helical windings are used for high-voltage transformer windings at very high voltage ratings, commonly 110 kV and above.
Correct answer: for 110 kV and above- A. distribution transformers
- B. power transformers
- C. shell type transformers
- D. none of the above
Explanation: Helical windings are suited to the high-current, relatively low-voltage windings commonly found in power transformers.
Correct answer: power transformers- A. short capacity transformers
- B. medium capacity transformers
- C. high capacity transformers
- D. any of the above
Explanation: Disc windings use short, heavily insulated rectangular conductors and provide good mechanical strength and cooling, making them suitable…
Correct answer: high capacity transformers135. 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
Explanation: Forced oil and air circulation is used when natural cooling is insufficient for very large transformers, typically those rated 30 MVA and…
Correct answer: 30 MVA upwards- A. Corrugations
- B. Fins
- C. Tubes
- D. Radiator tanks
- E. All of the above
Explanation: Corrugations, fins, tubes and radiator tanks all increase the external surface area available for heat transfer from transformer oil to…
Correct answer: All of the above- A. 2 MVA
- B. 5 MVA
- C. 7.5 MVA
- D. 10 MVA
Explanation: Natural cooling with radiator systems is commonly used for transformers up to about 10 MVA; larger units generally require forced oil or…
Correct answer: 10 MVA- A. Electrical considerations
- B. Mechanical considerations
- C. Thermal considerations
- D. All of the above
Explanation: Transformer insulation must withstand electrical stress, retain mechanical strength against short-circuit forces, and tolerate thermal…
Correct answer: All of the above- A. 1.5 to 2.5 A/mm2
- B. 3.5 to 4.5 A/mm2
- C. 4.0 to 5.0 A/mm2
- D. 5.4 to 6.2 A/mm2
Explanation: Forced oil circulation or water-cooled coils remove heat more effectively, allowing a higher winding current density than ordinary natural…
Correct answer: 5.4 to 6.2 A/mm2- A. 1.0 Wb/m2
- B. 1.1 Wb/m2
- C. 1.3 Wb/m2
- D. 1.6 Wb/m2
- E. None of the above
Explanation: Cold-rolled grain-oriented steel has low core loss and can operate at a comparatively high flux density.
Correct answer: 1.6 Wb/m2