Related Questions

If in a synchronous motor, driving a given mechanical load and drawing current at a leading power factor from constant voltage supply its field excitation is increased, its power factor
A will become more
B will become less
C will remain unchanged
D none of the above.
If in a synchronous motor, driving mechanical load and drawing current at lagging power factor from constant voltage supply, its field excitation is increased, then its power factor
A become more
B become less
C remain constant
D none of the above
When a D.C. series motor is connected to A.C. supply, the power factor will be low because of
A high inductance of field and armature circuits
B induced current in rotor due to variations of flux
C fine copper wire winding
D none of the above
A power supply which has voltage regulation of ___________ is unregulated power supply
A 0%
B 5%
C 10%
D 8%
A synchronous motor installed at the receiving end substation operates with such an excitation that it takes power at lagging power factor. Now if the applied voltage of the synchronous motor goes down, the power factor of the synchronous motor will
A remain same
B go down
C improve
D none of the above
What is the effect on the performance of the economiser in the thermal power plant boiler, if the feed water temperature is very low due to preheaters being out for repairs or starving of steam supply ?
A It results in corrosion due to the condensation on the flue gas side of the economiser tubes due to handling of low temperature water
B Economiser tube life increases due to handling of low temperature water
C Heat transfer efficiency of economiser increases due to picking up high heat from the flue gases
D Scale formation rate on economiser tubes increases
Which of the following power plants need the least period for installation ?
A Thermal power plant
B Diesel power plant
C Nuclear power plant
D Hydro-electric power plant
Installation of supercharger on a four cycle diesel engine can result in the following percentage increase in power
A Up to 35%
B Up to 50%
C Up to 75%
D Up to 100%
The low power factor of induction motor is due to
A Rotor leakage reactance
B Stator reactance
C The reactive lagging magnetizing current necessary to generate the magnetic flux
D All of the above
Which of the following is the disadvantage due to low power factor ?
A Poor voltage regulation
B Increased transmission losses
C High cost of equipment for a given load
D All of the above

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