Free Power Systems MCQs with Answers

• A. induction motors
• B. resistive loads
• C. synchronous Motors
• D. all of the above

Explanation: Induction motors draw magnetizing reactive power, which lowers the supply power factor.

• A. maximum demand/average load
• B. average load x maximum demand
• C. average load/maximum demand
• D. none of the above

Explanation: Load factor compares the average load carried by a station with its maximum demand: load factor = average load ÷ maximum demand.

• A. 532 k cal.
• B. 735 k cal.
• C. 746 k cal.
• D. 860 k cal.

Explanation: One kilowatt-hour equals 3.6 MJ, and 1 kcal is approximately 4.187 kJ; hence 3,600 ÷ 4.187 is about 860 kcal.

• A. high
• B. low
• C. remain same
• D. none of the above

Explanation: For a given real power, a low power factor requires higher current, increasing conductor and equipment ratings and losses.

• A. reducing the work done
• B. increasing the rotor speed
• C. reducing the rotor speed
• D. balancing the turbine

Explanation: Compounding divides the steam expansion among several stages so that the excessive velocity or pressure drop of a single stage is avoided.

• A. 0.8 to 1.0
• B. 1.0 to 1.05
• C. 1.1 to 1.5
• D. above 1.5

Explanation: The reheat factor is greater than unity because the cumulative actual stage enthalpy drops exceed the overall isentropic enthalpy drop.

• A. isentropic heat drop to useful heat drop
• B. adiabatic heat drop to isentropic heat drop
• C. cumulative actual enthalpy drop for the stages to total is isentropic enthalpy heat drop

Explanation: Reheat factor equals the sum of the actual enthalpy drops in all turbine stages divided by the overall isentropic enthalpy drop.

• A. Deaerative heating is done to
• B. heat the water
• C. heat the air in the water
• D. remove dissolved gases in the water

Explanation: Deaerative heating heats feedwater close to its saturation condition so that dissolved oxygen and other corrosive gases are released.

• A. to reduce the boiler pressure
• B. to increase the steam temperature
• C. to control the solid concentration in the boiler water by removing some of the concentrated saline water
• D. none of the above

Explanation: Boiler blowdown removes a portion of concentrated boiler water, controlling the buildup of dissolved salts and suspended solids.

• A. 50-75 kg/m per hour
• B. 75-100 kg/m per hour
• C. 100-150 kg/m per hour
• D. 150-200 kg/m2 per hour

Explanation: A traveling-grate stoker commonly burns coal at approximately 150 to 200 kg per square metre of grate area per hour.

• A. underfeed stoker
• B. overfeed stoker
• C. any

Explanation: Overfeed stokers suit large boilers burning unpulverised coal because coal is fed above the grate and can be supplied continuously in…

• A. chain grate
• B. spreader
• C. travelling grate
• D. all of the above

Explanation: Chain-grate, spreader, and travelling-grate stokers all feed coal onto the upper surface of the burning fuel bed, so each is an overfeed…

• A. anthracite
• B. lignite
• C. semibituminous and bituminous

Explanation: Underfeed stokers are suitable for semibituminous and bituminous coals because these coals contain relatively high volatile matter and can…

• A. unit
• B. central
• C. none of the above

Explanation: In a central system, one central pulverizer prepares the fuel and sends it to a bunker before distribution to individual burners.

• A. primary air
• B. secondary air
• C. tertiary air

Explanation: Secondary air is introduced around or above the fuel stream to supply the oxygen needed to complete combustion.

• A. carrying coal in horizontal direction
• B. carrying coal in vertical direction
• C. carrying coal in any direction

Explanation: A bucket elevator carries bulk material in buckets along a vertical path, lifting coal from a lower level to a higher one.

• A. lift trucks
• B. coal accelerators
• C. tower cranes
• D. belt conveyor

Explanation: Coal accelerators are used to unload coal in small power plants by rapidly discharging it from transport vehicles or containers.

• A. 20 to 40 tonnes/hr
• B. 50 to 100 tonnes/hr
• C. 100 to 150 tonnes/hr
• D. 150 to 200 tonnes/hr

Explanation: A typical belt conveyor used in coal handling has a capacity of roughly 50 to 100 tonnes per hour, although the actual value depends on…

• A. dust
• B. clinkers
• C. iron particles
• D. sand

Explanation: Magnetic separators attract ferrous contaminants, particularly iron particles, from coal before it reaches crushers and other equipment.

• A. reduce the flame length
• B. increase the flame length
• C. transport and dry the coal
• D. provide air round the burners for getting optimum combustion

Explanation: Secondary air is admitted around the burner to provide sufficient oxygen and mixing for complete, well-controlled combustion.