This set of Power Electronics Multiple Choice Questions & Answers (MCQs) focuses on “Choppers-1″.
1. In the ___________ type of chopper, two stage conversions takes place.
b) AC link
c) DC link
d) None of the mentioned
2. Choppers converter
a) AC to DC
b) DC to AC
c) DC to DC
d) AC to AC
Explanation: 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
Explanation: 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?
d) All of the mentioned
Explanation: 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
Explanation: 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 ?
d) Toff x Ton
Explanation: 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
Explanation: The output voltage can be changed by changing the duty cycle (Ton/T).
8. The values of duty cycle (α) lies between
Explanation: 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
Explanation: 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
Explanation: The chopper output voltage is Duty cycle x the input voltage (ideal condition).
Sanfoundry Global Education & Learning Series – Power Electronics.
To practice all areas of Power Electronics, here is complete set of 1000+ Multiple Choice Questions and Answers.