Electrician Theory Solved Paper ||Sem-3rd // Paper-1st // NCVT Exam July 2019 ||

Electrician Theory Solved Paper

Semester-3rd

Paper-1st 

Q.No.-01-25

NCVT Exam July 2019

1. Which speed is called as synchronous speed in 3 phase induction motor?
(A)  No load speed
(B)  Full load speed
(C)  Rotating magnetic field speed
(D) Relative speed between stator and rotor

Ans:-(C)

2. What is the formula to calculate the slip speed (Nslip) of 3 phase squirrel cage induction motor?
(A)  N_slip = N_s -N_r 
(B)  N_slip = N_r -N_s 
(C)  N_slip = N_s -N_r/N_r 
(D)  N_slip = Ns – Nr/Ns 
Ans:-(A)

3. What is the name of the starter symbol?  

(A)  D.O.L starter
(B)  Auto transformer starter
(C)  Automatic star / delta starter
(D)  Semi automatic star / delta starter 
Ans:-(B)

4. Determine the torque in newton meters produced by a 7.5 HP squirrel cage motor rotating at 1440 rpm? 

(A)  21.63 Nm

(C)  33.05 Nm

(B)  24.4 Nm

(D)  36.6 Nm

Ans:-(D)

5. Which type of handle design of rotary switch is illustrated?  

(A)  Knob

(B)  Lever

(C)  Coin slot

(D)  Key operation

Ans:-(C)

6. What is the purpose of using rotor resistance starter to start 3 phase slip ring induction motor? 

(A)  Reduce rotor voltage

(B)  Reduce rotor current  

(C)  Increase the torque

(D)  Reduce the power loss

Ans:-(C)

 

7. Which is the cause for the 3 phase motor starter with single phase preventer trips frequently? 

(A)  Incorrect fuse ratings

(B)  Unbalanced line voltages

(C)  Incorrect settings of OLR

(D)  Improper phase sequence

Ans:-(C)

 

8. Which method of speed control is only applicable for 3 phase slipring induction motor? 

(A)  Cascade operation method

(B)  Rotor rheostat speed control

(C)  Changing the applied frequency method

(D)  Changing the number of stator poles method

Ans:-(B)

9. Which type of single phase motor is illustrated? 

 

(A)  Universal motor

(B)  Permanent capacitor motor

(C)  Capacitor start induction run motor

(D)  Capacitor start capacitor run motor

Ans:-(D)

 

10. What is the application of shaded pole motor? 

(A)  Hair dryer

(B)  Ceiling fan

(C)  Wet grinder

(D)  Washing machine

Ans:-(A)

11. Which type of single phase motor is used for hard disk drives? 

(A)  Stepper motor

(B)  Repulsion motor

(C)  Hysteresis motor

(D)  Reluctance motor

Ans:-(A)

 

12. What is the function of centrifugal switch used in capacitor start, capacitor run induction motor? 

(A)  Disconnect the running winding after reached 75% to 80% speed

(B)  Disconnect the starting winding after reached 75% to 80% speed

(C)  Disconnect the starting capacitor after reached 75% to 80% speed

(D) Disconnect the starting and running winding  after reached 75% to 80% speed

Ans:-(C)

 

13. Which type of single phase motor is having very high starting torque than any other type of single phase motor? 

(A)  Universal motor

(B)  Reluctance motor

(C)  Repulsion start induction run motor

(D)  Capacitor start induction run motor 

Ans:-(A)

 

14. How the radio interference can be suppressed in centrifugal switch method of speed control of universal motor? 

(A)  By connecting capacitor across centrifugal switch

(B)  By connecting capacitor in series with centrifugal switch

(C)  By adding compensating winding with armature

(D)  By connecting an inductor in series with centrifugal switch

Ans:-(A)

 

15. What is the supply frequency of an alternator having 6 poles  runs at 1000 rpm? 

(A)  25 Hz

(B)  40 Hz

(C)  50 Hz

(D)  60 Hz

Ans:-(C)

 

16. Calculate the speed in r.p.s of the 2 pole, 50Hz alternator? 

(A)  50 rps

(B)  100 rps

(C)  1500 rps

(D)  3000 rps

Ans:-(A)

 

17. What is the advantage of using rotating field type alternator? 

(A)  Easy to locate the faults in the field

(B)  Easy to connect the load with alternator

(C)  Easy to dissipate the heat during running

(D)  Two slip rings only required irrespective of No.  of phases

Ans:-(D)

 

18. What is the effect in increasing the field excitation current in alternator? 

(A)  Prevents demagnetizing

(B)  Prime over speed reduces

(C)  Voltage regulation decreases

(D)  Alternator will be overloaded

Ans:-(A)

 

19. Which is the main application of synchronous motors? 

(A)  Elevators

(B)  Paper rolling mills

(C)  AC to DC converter

(D)  Power factor correction device

Ans:-(D)

 

20. Which insulating material used in winding is a highly non - hygroscopic and possess good electrical strength? 

(A)  Empire cloth

(B)  Triplex paper  

(C)  Millinex paper

(D)  Leatheroid paper

Ans:-(C)

 

21. What is the name of the winding?

(A)  Skew winding

(B)  Skein winding

(C)  Involute coil winding

(D)  Diamond coil winding

Ans:-(B)

 

22. What is the advantage of motor generator set? 

(A)  Noiseless

(B)  High efficiency

(C)  Low maintenance required

(D)  DC output voltage can be easily controlled

Ans:-(D)

 

23. What is the function of the part marked 'X' of the rotary converter?

  

(A)  Converts AC to DC

(B)  Reduces voltage drop

(C)  Helps to deliver without noise

(D)  Collects the delivered direct current

Ans:-(A)

 

24. Name the part marked 'X' of the winding machine?  

(A)  Mandrel

(B)  Wire feed

(C)  Wire guides

(D)  Spool carrier

Ans:-(A)

 

25. What is the electrical degree of 6 pole stator motor? 

(A)  360°

(C)  1080°

(B)  720°

(D)  1440° 

Ans:-(C)
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