MCQs on Electrical Drives

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01․ An elevator drive is required to operate in
one quadrant only.
two quadrants.
three quadrants.
four quadrants.

Elevator drive should have four quadrant operation. Elevator drives operate in four quadrants are forward motoring ( 1st quadrant ), forward braking ( 2nd quadrant ), reverse motoring ( 3rd quadrant ) and reverse braking ( 4th quadrant ).

02․ Electric drive is becoming more and more popular because
all of below.
it provide smooth and easy control.
it is cheaper in cost.
it is simple and reliable.

Electric drive have following advantages. 1. It is simple, clean, compact, and reliable. 2. It provides easy and smooth control, flexibility in layout, easy starting and facility for remote control. 3. It is cheaper in initial as well as in maintenance cost.

03․ The basic elements of a electric drive are
electric motor.
control system.
electrical motor and control system.
none of the above.

The system or motor which employed for motion control is called electric drive. Hence basic elements of an electric drive is electric motor and control system.

04․ Speed control by variation of field flux results in
constant power drive.
constant torque drive.
variable power drive.
none of the above.

Variation of field flux results in variable torque and constant power drive operation.

05․ A four quadrant operation requires
two full converters in series.
two full converters connected in parallel.
two full converter connected in back to back.
two semi converters connected in back to back.

Full converter is operated in two quadrants. Hence in order to obtain four quadrants the drive requires another two quadrants, this will obtained by reversal of current. Reversal of current can be done by connecting two full converters in back to back.

06․ 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?
55.9 ° C.
58° C.
56° C.
60° C.


07․ In 4 quadrant operation of a hoist 3rd quadrant represents
reverse motoring.
reverse braking.
forward braking.
forward motoring.

Quadrant 1 : forward braking. Quadrant 2 : forward motoring. Quadrant 3 : reverse motoring. Quadrant 4 : reverse braking.

08․ High braking torque produced in
dynamic braking.
regenerative braking.
none of above.

In plugging, in order to limit the armature current to a safe value an external current limiting resistor is connected thus armature current is reversed and high braking torque is produced.

09․ In case of kiln drives, starting torque is.
more than double of the running torque.
more than triple of the running torque.
almost equal to running torque.
less than running torque.

In kiln drives starting torque is double than that of running torque. Hence for kiln drives ward Leonard controlled DC shunt motors, slip ring IM, cascade controlled AC motors is employed.

10․ What are the constituents in speed time curve of train?
Initial acceleration.
Constant speed.
All of these.

Constituents of speed time curve is 1. Initial acceleration. 2. Constant speed / free running. 3. Coasting. 4. Retardation / braking.