POWER ELECTRONICS AND DRIVES PART 19

POWER ELECTRONICS AND DRIVES PART 19

1. The below given figure is that of a _________ (IGBT is used as a chopper switch)
a) step-up/step-down chopper
b) step-down chopper
c) step-up chopper
d) none of the mentioned
 
Answer: b

2. In the below given circuit, when switch (SW) is on
a) voltage is non-zero and current is rising
b) voltage is non-zero and current is decaying
c) voltage is zero and current is rising
d) voltage is zero and current is decaying
 
Answer: a

3. In the below given circuit, when switch (SW) is off

a) voltage is non-zero and current is rising
b) voltage is non-zero and current is decaying
c) voltage is zero and current is rising
d) voltage is zero and current is decaying
 
Answer: d

4. In a step down chopper, if Vs = 100 V and the chopper is operated at a duty cycle of 75 %. Find the output voltage.
a) 100 V
b) 75 V
c) 25 V
d) none of the mentioned
 
Answer: b

5. If Vo is the output voltage and Vs is the input DC voltage, then for the below given circuit.
a) Vo = Vs
b) Vo < Vs
c) Vo > Vs
d) Insufficient information
 
Answer: c

6. In the below given circuit, when switch (SW) is on
a) voltage is non-zero and current is rising
b) voltage is zero and current is decaying
c) voltage and current both are non-zero
d) voltage and current both are zero
 
Answer: c

7. In the below given circuit, when switch (SW) is first switched closed and then opened the
a) voltage is non-zero and current is rising
b) voltage is zero and current is decaying
c) voltage is non-zero and current is decaying
d) voltage is zero and current is rising
 
Answer: c

8. What is the voltage across the load when the SW is first closed and then opened?
 
a) Vs
b) duty cycle x Vs
c) Vs + L (di/dt)
d) zero
 
Answer: c

9. Find the expression for output voltage for a step-up chopper, assume linear variation of load current and α as the duty cycle.
a) Vs
b) Vs/α
c) Vs/(1-α)
d) Vs/√2
 
Answer: c
10. Find the output voltage for a step-up chopper when it is operated at a duty cycle of 50 % and Vs = 240 V.
a) 240 V
b) 480 V
c) 560 V
d) 120 V
 
Answer: b