1. Ward-Leonard control is basically a ?

voltage control method

field divertor method

field control method

armature resistance control method

Answer: voltage control method

Explanation:


2. Speed control by Ward Leonard method gives uniform speed variation ?

in one direction

in both directions

below normal speed only

above normal speed only

Answer: in both directions

Explanation:


3. Which one of the following is not the function of pole shoes in a D.C. machine ?

To reduce eddy current loss

To support the field coils

To spread out flux for better uniformity

To reduce the reluctance of the magnetic path

Answer: To reduce eddy current loss

Explanation:


4. Which D.C. motor will be suitable along with flywheel for intermittent light and heavy loads ?

Series motor

Shunt motor

Cumulatively compounded motor

Differentially compounded motor

Answer: Cumulatively compounded motor

Explanation:


5. Starters are used with D.C. motors because ?

these motors have high starting torque

these motors axe not self starting

back e.m.f. of these motors is zero initially

to restrict armature current as there is no back e.m.f. while starting

Answer: to restrict armature current as there is no back e.m.f. while starting

Explanation:


6. Which of the following application requires high starting torque ?

Lathe machine

Centrifugal pump

Locomotive

Air blower

Answer: Locomotive

Explanation:


7. The condition for maximum power in case of dc motor is ?

back e.m.f. = 2 x supply voltage

back e.m.f. = 1/2 x supply voltage

supply voltage = 1/2 x back e.m.f.

supply voltage= back e.m.f.

Answer: back e.m.f. = 1/2 x supply voltage

Explanation:


8. The speed of a motor falls from 1100 r.p.m. at no-load to 1050 r.p.m at rated load. The speed regulation of the motor is ?

2:36 %

4.76%

6. 77%

8.4%

Answer: 4.76%

Explanation:


9. The condition for maximum efficiency for a D.C. generator is ?

eddy current losses= stray losses

hysteresis losses= eddy current losses

copper losses = 0

variable losses = constant losses

Answer: variable losses = constant losses

Explanation:


10. Which method of braking is generally used in elevators ?

Plugging

Regenerative braking

Rheostatic braking

Nope of the above

Answer: Plugging

Explanation: