36. A lossy capacitor C_x, rated operation at 5 kV, 50 Hz is represented by an equivalent circuit with an ideal capacitor C_p is parallel with a resistor R_p. The value of C_p is found to be 0.102 μF and the value of R_p = 1.25 MΩ. Then the power loss and tan δ of the lossy capacitor operating at the rated voltage, respectively, are
    

1. 1. 10 W and 0.0002

   
   
   

   2. 10 W and 0.0025

   
   
   

   3. 20 W and 0.025

   
   
   

   4. 20 W and 0.04

   
   
   

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1. View Hint View Answer Discuss in Forum

   Power - loss =	V2		(5 KV)2	= 20 W
   	RP		1.25 MΩ

   
   

   tan δ =	1
   	ωCP RP

   
   

   =	1	= 0.025
   	(2π 50)(0.102 × 10-6)(1.25 × 106)

   
   
   

   Correct Option: C

   Power - loss =	V2		(5 KV)2	= 20 W
   	RP		1.25 MΩ

   
   

   tan δ =	1
   	ωCP RP

   
   

   =	1	= 0.025
   	(2π 50)(0.102 × 10-6)(1.25 × 106)

   
   
   

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37. Circuit turn-off time of an SCR is defined as the time
    (a)
    (b)
    (c)
    (d)
    

1. 1. taken by the SCR to turn off

   
   
   

   2. required for the SCR current to become zero

   
   
   

   3. for which the SCR is reverse biased by the commutation circuit

   
   
   

   4. for which the SCR is reverse biased to reduce its current below the holding current

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: C

   NA

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38. A three-phase current source inverter used for the speed control of an induction motor is to be realized using MOSFET switches as shown below. Switches S₁ to S₆ are identical switches.
    
    The proper configuration for realizing switches S₁ to S₆ is

1. 1. 
      

   
   
   

   2. 
      

   
   
   

   3. 
      

   
   
   

   4. 

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: C

   NA

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39. In the circuit shown, an ideal switch S is operated at 100 kHz with a duty ratio of 50%. Given that ∆i_c is 1.6 A peak-to-peak and I₀ is 5 A dc, the peak current in S is
    
    

1. 1. 6.6 A

   
   
   

   2. 5.0 A

   
   
   

   3. 5.8 A

   
   
   

   4. 4.2 A

   
   
   

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1. View Hint View Answer Discuss in Forum

   
   
   The size in inductor current during ON period.
   

   ∆IL =	Vs - V0	TON , TON =	L∆L
   	L		Vs - V0

   
   and during OFF - period
   

   -∆IL =	- V0	TOFF , TOFF =	L∆L
   	T		V0

   
   Switching frequency,
   

   f =	1	=	1	.	V0(Vs - V0)
   	TON + TOFF		L∆IL		Vs

   
   

   ⇒ ∆IL =	VsK(1 - K)	.K =	V0
   	fL		Vs

   
   The maximum source current is given by,
   

   Imax = Io +	∆L	= 5 +	1.6	= 5.8 A
   	2		2

   
   

   Correct Option: C

   
   
   The size in inductor current during ON period.
   

   ∆IL =	Vs - V0	TON , TON =	L∆L
   	L		Vs - V0

   
   and during OFF - period
   

   -∆IL =	- V0	TOFF , TOFF =	L∆L
   	T		V0

   
   Switching frequency,
   

   f =	1	=	1	.	V0(Vs - V0)
   	TON + TOFF		L∆IL		Vs

   
   

   ⇒ ∆IL =	VsK(1 - K)	.K =	V0
   	fL		Vs

   
   The maximum source current is given by,
   

   Imax = Io +	∆L	= 5 +	1.6	= 5.8 A
   	2		2

   
   

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40. The average on-state current for an SCR is 20 A for a conduction angle of 120°. The average on state current for 60° conduction angle will be ______A .

1. 1. 10

   
   
   

   2. 20

   
   
   

   3. 30

   
   
   

   4. 40

   
   
   

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1. View Hint View Answer Discuss in Forum

   Iav =	Im
   	form factor

   
   where, form factor for 120° = 1.878 and form factor for 60° = 2.7781
   So, I_av is less than 20 A

   Correct Option: B

   Iav =	Im
   	form factor

   
   where, form factor for 120° = 1.878 and form factor for 60° = 2.7781
   So, I_av is less than 20 A

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