250+ TOP MCQs on Choppers-1 and Answers

Power Electronics Multiple Choice Questions on “Choppers-1″.

1. In the ___________ type of chopper, two stage conversions takes place.
A. AC-DC
B. AC link
C. DC link
D. None of the mentioned
Answer: In AC link chopper, DC is converter to AC than stepped up/down than again AC to DC conversation takes place.

2. Choppers converter
A. AC to DC
B. DC to AC
C. DC to DC
D. AC to AC
Answer: C
Clarification: Choppers are used to step up or step down DC voltage/current levels. Hence, they are DC to DC converters.

3. A chopper may be thought as a
A. Inverter with DC input
B. DC equivalent of an AC transformer
C. Diode rectifier
D. DC equivalent of an induction motor
Answer: B
Clarification: It is a DC equivalent of an AC transformer because it behaves in the similar manner i.e. converting fixed DC to variable DC.

4. Which device can be used in a chopper circuit?
A. BJT
B. MOSFET
C. GTO
D. All of the mentioned
Answer: D
Clarification: All of the devices which can be used as a switch can be used in a chopper.

5. A chopper is a
A. Time ratio controller
B. AC to DC converter
C. DC transformer
D. High speed semiconductor switch
Answer: D
Clarification: It is a high speed on/off semiconductor switch. Note that it behaves like a DC transformer, does not mean it is a DC transformer. There is no DC transformer.

6. What is the duty cycle of a chopper ?
A. Ton/Toff
B. Ton/T
C. T/Ton
D. Toff x Ton
Answer: B
Clarification: It is the time during which the chopper is on (Ton) relative to the whole period (T = Ton+Toff).

7. The load voltage of a chopper can be controlled by varying the
A. duty cycle
B. firing angle
C. reactor position
D. extinction angle
Answer: A
Clarification: The output voltage can be changed by changing the duty cycle (Ton/T).

8. The values of duty cycle (α) lies between
A. 0<α<1
B. 0>α>-1
C. 0<=α<=1
D. 1<α<100
Answer: C
Clarification: The duty cycle is between 0 and 1. It can be 0 if the chopper switch is never on and it can be 1 when the chopper switch is always on.

9. If T is the time period for a chopper circuit and α is its duty cycle, then the chopping frequency is
A. Ton/α
B. Toff/α
C. α/Toff
D. α/Ton
Answer: D
Clarification: α = Ton/T
T = Ton/ α
f = 1/T = α/Ton.

10. Find the output voltage expression for a step down chopper with Vs as the input voltage and α as the duty cycle.
A. Vo = Vs/α
B. Vo = Vs x α
C. Vo = Vs²/α
D. Vo = 2Vs/απ
Answer: B
Clarification: The chopper output voltage is Duty cycle x the input voltage (ideal condition).