Free Electrical Machines MCQs with Answers

• A. Light duty
• B. Medium duty
• C. Heavy duty
• D. All of the above

Explanation: Ward-Leonard DC drives provide high starting torque, smooth speed control and easy reversal, making them suitable for heavy-duty…

• A. Starting torque
• B. Conditions of environment
• C. Limitation on starting current
• D. Speed control range and its nature
• E. All of the above

Explanation: Motor and control-gear selection must consider the required starting torque, environmental conditions, allowable starting current and the…

• A. variable load
• B. continuous
• C. continuous but periodical
• D. intermittent and variable load

Explanation: A power press draws load only during the pressing stroke and the load also changes during that stroke, with idle or lighter periods…

• A. Running characteristics
• B. Starting characteristics
• C. Efficiency
• D. Braking

Explanation: A floor mill needs suitable starting and running characteristics and good efficiency for economical operation.

• A. Electrical characteristics
• B. Mechanical characteristics
• C. Size and rating of motors
• D. Cost
• E. All of the above

Explanation: Motor selection involves electrical performance, mechanical requirements, physical size and rating, and economic cost.

• A. Squirrel cage induction motor
• B. Synchronous motors
• C. Ward-Leonard controlled D.C. motors
• D. Any of the above

Explanation: Ward-Leonard drives provide smooth, wide-range speed control, rapid reversal and good automatic control, making them suitable for…

• A. 2 kW
• B. 20 kW
• C. 50 kW
• D. 100 kW

Explanation: Synchronous motors become economically attractive for large loads, commonly above about 100 kW, because their higher cost is offset by…

• A. Power houses
• B. Pumping stations
• C. Automobile workshops
• D. All of the above

Explanation: Light-duty cranes are used for handling lighter loads in power houses, pumping stations and automobile workshops.

• A. Slow speed motors
• B. Continuous duty motors
• C. Short time rated motors
• D. None of the above

Explanation: Overhead travelling cranes operate intermittently with frequent starting, stopping and reversing, so their motors are designed for…

• A. 15-20
• B. 50-75
• C. 120-150
• D. 160-200

Explanation: Suburban trains make frequent stops and starts, so their specific energy consumption is higher than that of long-distance services; a…

• A. 0.2 to 0.5 km phps
• B. 1.6 to 4.0 km phps
• C. 5 to 10 km phps
• D. 15 to 25 km phps

Explanation: Suburban and urban trains require relatively high acceleration to maintain schedules despite frequent stops, typically about 1.6 to 4.0…

• A. Reduced current method
• B. Tap changing control of transformer
• C. Series parallel operation of motors
• D. All of the above

Explanation: A 25 kV, 50 Hz single-phase traction system controls locomotive speed mainly by changing the transformer tap, which varies the voltage…

• A. 0.16 km phps
• B. 1.6 km phps
• C. 16 km phps
• D. 40 km phps

Explanation: During coasting, train resistance produces only a small deceleration, typically around 0.16 km/h/s.

• A. 0.3
• B. 0.26
• C. 0.225
• D. 0.16

Explanation: Wet rails reduce adhesion below the dry-rail value, so the coefficient must be less than 0.26; a commonly used wet-rail value is about…

• A. Three phase A.C. is converted into D.C.
• B. Single phase A.C. is converted into D.C.
• C. Single phase supply is converted into three phase system
• D. None of the above

Explanation: The Kando system takes single-phase AC from the overhead supply and converts it into a three-phase supply for traction motors.

• A. directly through overhead electric line
• B. through individual generator of bogie and batteries
• C. through rails
• D. through locomotive

Explanation: Passenger-coach lighting is normally supplied by an axle-driven generator mounted on the bogie, with batteries providing storage and…

• A. 150 to 175 kg
• B. 100 to 120 kg
• C. 60 to 80 kg
• D. 28 to 30 kg

Explanation: A steam locomotive consumes roughly 28 to 30 kg of coal per kilometre under average operating conditions.

• A. electrical-pneumatic
• B. mechanical-electrical
• C. hydro-mechanical
• D. hydro-pneumatic

Explanation: Suri transmission is a hydro-mechanical transmission, combining hydraulic power transfer with mechanical gearing.

• A. 60 Hz
• B. 50 Hz
• C. 25 Hz
• D. 16 Hz

Explanation: The standard 25 kV railway electrification system uses single-phase AC at 50 Hz, matching the normal power-system frequency used in…

• A. uneven distribution of tractive effect
• B. suitability for passanger as well as freight service
• C. lot of skidding
• D. low co-efficient of adhesion

Explanation: A monomotor bogie uses one traction motor to drive both axles of the bogie, making it suitable for both passenger and freight operation.