The input of an ac circuit having pf of 0.8 lag is 20 KVA. The power drawn by the circuit is .........KW

The input of an ac circuit having pf of 0.8 lag is 20 KVA. The power drawn by the circuit is .........KW

A. 12
B. 20
C. 16
D. 8

Explanatory answer:

 KVA= VI*10^3

Power  = VI * PF

Power drawn = KVA*PF = 20 * 0.8 = 16 KW

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An SCR carrying a current of 5 A, the increase in load demands the anode current to rise to 50 A in 2 micro seconds. di/dt rating of SCR is 20 A per microsecond and maximum current rating is 60 A.Comment ,under this condition what happens to SCR.

An SCR carrying a current of 5 A, the increase in load demands the anode current to rise to 50 A in 2 micro seconds. di/dt rating of SCR is 20 A per microsecond and maximum current rating is 60 A.Comment ,under this condition what happens to SCR.

Explanatory answer: 


given, di/dt rating of SCR = 20 A/ us

but actual di/dt = 50 A per 2 microseconds =50/2 = 25 A/ us

Thus the actual di/dt is greater than the di/dt rating of SCR. This will lead to damage of SCR.

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Match the pairs with respect to a thyristor

Match the pairs with respect to a thyristor

Answer:  

(i)-c
(ii)-d
(iii)-b
(iv)-a

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The power electronic converter shown in figure has a single-pole-double-throw switch. The pole P of the switch is connected alternatively throws A and B. The converter shown is a

The power electronic converter shown in figure has a single-pole-double-throw switch. The pole P of the switch is connected alternatively throws A and B. The converter shown is a

A. step-down chopper (buck converter)
B. half-wave rectifier
C. step-up chopper (boost converter)
D. full wave rectifier.       (GATE-EE-2010)

Answer: It is a step-down chopper

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A sine wave of voltage varies from zero to maximum of 200 V. How much is the voltage at the instant of 30 deg of the cycle ?

A sine wave of voltage varies from zero to maximum of 200 V. How much is the voltage at the instant of 30 deg of the cycle ?

A. 50 V
B. 82.8 V
C. 100 V
D. 173.2 V


Explanatory answer:

In general, Sine wave form is represented as Vm sin wt.

Vm = 200

at 30 deg,  200 sin (30) = 100 V

Ans: 100 V

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