Power Electronics Questions and Answers – Choppers-5

This set of tricky Power Electronics questions and answers focuses on “Choppers-5”.

1. In the figure shown below, the capacitor C is used to
The capacitor C is used maintain the load voltage constant
a) maintain the load voltage constant
b) protect the load
c) protect the chopper switch (SW)
d) maintain the load current constant
View Answer

Answer: a
Explanation: It is a step-up/step-down chopper, the C maintains the load voltage constant.

2. In the below shown step-up/step-down chopper circuit, when the switch (SW) is on
q4.png”>The capacitor C is used maintain the load voltage constant
a) current through inductor rises and the load voltage is zero
b) current through inductor rises and the load voltage is Vs
c) current through inductor decays and the load voltage is zero
d) current through inductor decays and the load voltage is Vs
View Answer

Answer: b
Explanation: During Ton, current flows from Vs-CH-L-Vs. Current through L rises from I1 to I2 and Vs appears across the inductor and load as they are in parallel. Voltage drop at the diode has to be considered as zero.

3. For a step-up/step-down chopper, if α (duty cycle) < 0.5 then
a) Vo = Vs
b) Vo < Vs
c) Vo > Vs
d) none of the mentioned
View Answer

Answer: b
Explanation: Vo = Vs (α/1-α)
For duty cycle is less than 0.5, the circuit behaves like a step down chopper. Hence, Vo < Vs.
advertisement
advertisement

4. In the below shown step-up/step-down chopper circuit, when the chopper switch (SW) if first on and then off, then the current flows from path
q4.png”>The capacitor C is used maintain the load voltage constant
a) Vs-CH-L-Vs
b) L-Load-D-L
c) L-D-Load-L
d) no current flows
View Answer

Answer: b
Explanation: When the chopper switch is off, polarity of emf induced in the inductor L gets reversed biased. Emf induced in L forward biases the diode D and L starts to discharge from inductor-load-diode-inductor.

5. For a step-up/step-down chopper, if current increases from I1 to I2 linearly during Ton, then find the energy stored in the inductor during Ton
a) zero
b) Vs x (I1 + I2)
c) Vs x [ (I1 + I2)/2 ] x Ton
d) Vs x [ (I1 + I2)/2 ] x T
View Answer

Answer: c
Explanation: Iavg = [ (I1 + I2)/2 ] Energy stored = Win = Vs x [ (I1 + I2)/2 ] x Ton.
Note: Join free Sanfoundry classes at Telegram or Youtube

6. A step-down chopper is also called as a
a) first-quadrant chopper
b) second-quadrant chopper
c) third-quadrant chopper
d) fourth-quadrant chopper
View Answer

Answer: a
Explanation: It is called as a first quadrant chopper as the current always flows from source to load and the current and voltage both are always positive.

7. For the type-B chopper shown below
During Ton, SW is on & vo = 0 as the switch S.C’s the load for the type-B chopper
a) during Ton, Vo = 0 and L stores energy
b) during Ton, Vo is not 0 and L stores energy
c) during Ton, Vo = 0 and L releases energy
d) during Ton, Vo is not 0 and L releases energy
View Answer

Answer: a
Explanation: During Ton, SW is on and vo = 0 as the switch S.C’s the load. E drives current through L and charges it.
advertisement

8. For the type-B chopper shown below
During Ton, SW is on & vo = 0 as the switch S.C’s the load for the type-B chopper
a) during Toff, Vo = (E + Ldi/dt) and D is conducting
b) during Toff, Vo = (E + Ldi/dt) and D is not-conducting
c) during Toff, Vo = 0
d) during Toff, Vo = Vs
View Answer

Answer: a
Explanation: When switch Is off, Vo = E + Ldi/dt exceeds source voltage Vs and D (diode) is forward biased and begins to conduct.

9. The below given chopper is that of a
During Ton, SW is on & vo = 0 as the switch S.C’s the load for the type-B chopper
a) step-up chopper
b) step-down chopper
c) step-up/step-down chopper
d) depends on the duty cycle
View Answer

Answer: a
Explanation: The load voltage Vo = E + L(di/dt) is greater than Vs, hence it is a step-up chopper.
advertisement

10. The type-C chopper or two quadrant type-A chopper has
a) type-A and type-B choppers in series
b) type-A and type-B choppers in parallel
c) two type-A choppers in series
d) two type-A choppers in parallel
View Answer

Answer: b
Explanation: The type-C chopper is a two quadrant chopper, it operates in the 1st and the 2nd quadrant. It has type-A and type-B choppers connected in parallel.

Sanfoundry Global Education & Learning Series – Power Electronics.

To practice tricky questions and answers on all areas of Power Electronics, here is complete set of 1000+ Multiple Choice Questions and Answers.

advertisement
advertisement
Subscribe to our Newsletters (Subject-wise). Participate in the Sanfoundry Certification contest to get free Certificate of Merit. Join our social networks below and stay updated with latest contests, videos, internships and jobs!

Youtube | Telegram | LinkedIn | Instagram | Facebook | Twitter | Pinterest
Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

Subscribe to his free Masterclasses at Youtube & discussions at Telegram SanfoundryClasses.