21.
Electric drive is becoming more and more popular because
A
it is simple and reliable
B
it provide smooth and easy control
C
it is cheaper in cost
D
All of the below
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Electric drive is becoming more and more popular because
it is simple and reliable
it provide smooth and easy control
it is cheaper in cost
All of the below
An elevator drive is required to operate in
three quadrants
one quadrant only
two quadrants
four quadrants
A motor has a thermal heating time constant of 50 mm. When the motor runs continuous of full scale, its final temperature rise is 80° C, what would be the temperature rise after 1 hour, if the motor runs continuously on full load?
56 degrees
55.9 degrees
58 degrees
60 degrees
A four quadrant operation requires
two full converter connected in back to back
two full converters in series
two full converters connected in parallel
two semi converters connected in back to back
A 3 - F induction motor draws an electric current of 50 A from mains when starts by direct switching. If an auto transformer with 60 % tapping is used for starting the electric current drawn from the mains will be
50
18
36
80
To save energy during braking ................. braking is used?
regenerative
dynamic
plugging
All of the above