WorksheetsPower Electronics_Unit-IV_DC-DC Converters_Day to Day Assessment
Total questions: 30
Worksheet time: 15mins
Choppers are used to control the DC voltage level.
True
False
Which one of the following device is uncontrolled?
SCR
MOSFET
Diode
TRIAC
What is the formula for output voltage for Buck converter?
8D*Vin
5D*Vin
2D*Vin
D*Vin
What is the formula for output voltage for Buck-Boost converter?
D*Vin
Vin/(1-D)
D*Vin/(1-D)
D*Vin/(1+D)
What is the formula for output voltage for Boost converter?
8D*Vin
5D*Vin
2D*Vin
D*Vin
Buck-Boost acts as Buck converter for duty cycle is equal to _________
0.9
0.7
0.6
0.4
Buck-Boost acts as Boost converter for duty cycle is equal to _________
0.8
0.1
0.2
0.4
Inductor and Capacitor in Buck converter are used to ___________
Increase the cost
Decrease the cost
Filter out the harmonics
Increase the Harmonics
In the ___________ type of chopper, two stage conversions takes place.
AC-DC
AC link
DC Link
None of the mentioned
Choppers converts
AC to DC
DC to AC
DC to DC
AC to AC
A chopper may be thought as a
Inverter with DC Input
DC Equivalent of an AC Transformer
Diode Rectifier
DC equivalent of an Induction Motor
Which device can be used in a chopper circuit?
BJT
MOSFET
GTO
All of the mentioned
What is the duty cycle of a chopper ?
Ton/Toff
Ton/T
T/Ton
Toff * Ton
The load voltage of a chopper can be controlled by varying the
Duty Cycle
Firing angle
Reactor position
Extinction angle
The values of duty cycle (δ) lies between
0<δ<1
0>δ>-1
0<=δ<=1
1<δ<100
If T is the time period for a chopper circuit and δ is its duty cycle, then the chopping frequency is
Ton/δ
Toff/δ
δ/Toff
δ/Ton
In a step down chopper, if Vs = 100 V and the chopper is operated at a duty cycle of 75 %. Find the output voltage.
100V
75V
25V
10V
The output voltage of all DC converters is directly proportional to the duty cycle.
True
False
Find the output voltage for a step-up chopper when it is operated at a duty cycle of 50 % and Vs = 240 V
240V
480V
560V
120V
If a step up chopper’s switch is always kept off then (ideally)
Vo = 0
Vo = ∞
Vo = Vs
Vo > Vs
For a step-down chopper, find the rms value of output voltage. Let δ be the duty cycle and Vs be the input voltage.
δ x Vs
Vs/δ
√δ x Vs
Vs/2
A step-up chopper has input voltage of 220 V and output voltage of 660 V. If the conducting time of the IGBT based chopper is 100 μs, compute Toff width of the output voltage pulse.
100 μs
150 μs
50 μs
10 μs
For a step-up chopper, when the duty cycle is increased the average value of the output voltage
Increases
Decreases
Remains the same
gets squared
Calculate the output voltage of the Buck converter if the supply voltage is 789 V and duty cycle value is .9
711.1V
710.1V
722.2V
713.2V
Calculate the output voltage of the Boost converter if the supply voltage is 156 V and duty cycle value is .4.
260V
264V
261V
268V
For a step-up/step-down chopper, if the duty cycle > 0.5 then
Vo = Vs
Vo < Vs
Vo > Vs
None of the mentioned
A step down chopper has input dc voltage of 220 V and R = 10 Ω in series with L = 65 mH. If the load current varies linearly between 11 A and 17 A, then find the duty cycle δ.
1
0.4
0.6
0.7
A step-down chopper is also called as a
First-quadrant chopper
Second-quadrant chopper
Third quadrant chopper
Fourth quadrant chopper
In case of TRC (Time Ratio Control), _________ is varied
Duty cycle
Firing angle
Supply frequency
Supply voltage magnitude
In case of variable frequency system __________ is varied
T
Ton
Toff
Supply frequency
