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Electrical Engineering Objective Questions { DC Motors }

288.  Which of the following loss of D.C.motor decreases with increase in load?
A. Friction and windage loss
B. Core loss
C. Brush contact loss
D. none of the above
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289.  In an overloaded motor main danger arises due to
A. winding getting overheated
B. busbars getting heated
C. starter getting damaged
D. bearing getting overheated
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290.  A wide and very sensitive speed control is usually required in case of
A. elevators
B. steel rolling mills
C. colliery winders
D. all of the above
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291.  For which application a D.C. motor is preferred over an A.C. motor?
A. High speed operation
B. Low speed operation
C. Fixed speed operation
D. Variable speed operation
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292.  Regenerative braking on D.C. shunt motors is used when
A. the load has overhauling characteristics
B. the load is variable
C. the load also acts as a braking force
D. the load is constantly decreasing
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293.  Which motor should be used for centrifugal pumps?
A. Series motor
B. Shunt motor
C. Either of the above
D. None of the above
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294.  Which of the following methods is most effective in finding out the no load losses in a large D.C. shunt motor?
A. Field's test
B. Ward-Leonard test
C. Block rotor test
D. Swinburne's test
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