51. An inverter has a periodic output voltage with the output waveform as shown in the given figure.
    When conduction angle α = 120°, then rms fundamental component of output voltage is
    
    

1. 1. 0.78 V
      

   
   
   

   2. 1.10 V
      

   
   
   

   3. 0.90 V
      

   
   
   

   4. 1.27 V

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: A

   NA

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52. A single-phase full-bridge voltage source inverter feeds a purely inductive load, as shown in the given figure, where T₁, T₂, T₃, T₄ are power transistors and D₁, D₂, D₃, D₄ are feedback diodes. The inverter is operated in square-wave mode with a frequency of 50 Hz. If average load current is zero, what is the time duration of conduction of each feedback diode in a cycle?
    
    

1. 1. 5 msec

   
   
   

   2. 10 msec

   
   
   

   3. 20 msec

   
   
   

   4. 2.5 msec

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: D

   NA

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53. An ac induction motor is used for a speed control application. It is driven from an inverter with a constant V/f control. The motor name-plate details are as follows :
    V = 415 V, Ph = 3, f = 50 Hz, N = 2850 rpm
    The motor is run with the inverter output frequency set at 40 Hz, and with half the rated slip. The running speed of the motor is
    

1. 1. 2400 rpm

   
   
   

   2. 2280 rpm

   
   
   

   3. 2340 rpm

   
   
   

   4. 2790 rpm

   
   
   

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1. View Hint View Answer Discuss in Forum

   Given : N_s = 3000 rpm
   

   ∴ s =	3000 - 2850	=	150	= 0.05
   	3000		3000

   
   

   Now , Ns = Ns	40	= 2400 rpm
   	50

   
   

   ∴ Running speed of the motor, Nr =		1 -	s		. Ns' = (1 - 0.025) . 2400 = 2340 rpm
   			2

   
   

   Correct Option: C

   Given : N_s = 3000 rpm
   

   ∴ s =	3000 - 2850	=	150	= 0.05
   	3000		3000

   
   

   Now , Ns = Ns	40	= 2400 rpm
   	50

   
   

   ∴ Running speed of the motor, Nr =		1 -	s		. Ns' = (1 - 0.025) . 2400 = 2340 rpm
   			2

   
   

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54. The speed/torque regimes in a dc motor and the control methods suitable for the same are given respectively in Group II and Group I
    

    Group I	Group II
    P. Field Control	1. Below base speed
    Q. Armature Control	2. Above base speed
    	3. Above base torque
    	4. Below base torque

    
    The match between the control method and the speed/torque regime is
    

1. 1. P-1; Q-3

   
   
   

   2. P-2; Q-1

   
   
   

   3. P-2; Q-3

   
   
   

   4. P-1; Q-4.

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: B

   NA

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55. The latching current of SCR is 18 mA. Its holding current will be ______ mA .

1. 1. 3

   
   
   

   2. 6

   
   
   

   3. 7

   
   
   

   4. 21

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: B

   NA

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