NEW
Font size
WorksheetsPower Electronics 4
Total questions: 10
Worksheet time: 5mins
Which PWM technique is most commonly used in PFC circuits?
Single-pulse modulation
Sinusoidal PWM
Hysteresis control
Space vector modulation
A step- down chopper has Vs = 230 V and R = 10 Ω. For a duty cycle of 0.4, the
power taken by the chopper is 2097 Watts. Find the chopper efficiency. Take the
voltage drop across the chopper switch as 2 V.
98 %
89.96 %
99.14 %
96.54
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
Insufficient data
The buck regulator has an input voltage of Vs = 12V. The required average output
voltage is Va = 5V at R = 500 Ω and the peak-to-peak output ripple voltage is 20 mV.
The switching frequency is 25 kHz. If the peak-to-peak ripple current of inductor is
limited to 0.8 A, determine the filter inductance L (in µH)
145.83
160.70
200.40
250.10
Which of the following techniques are used to improve the power factor?
extinction angle control
symmetrical angle control
Both
None
What is the purpose of using a phase-locked loop (PLL) in a PWM rectifier control
system?
To synchronise the switching frequency with the grid frequency
To regulate the output voltage
To minimise the harmonic distortion
To adjust the power factor
In case of a constant frequency system, Ton = (1/4)T. If the chopping frequency 2
kHz, find the value of Toff.
(1/8) ms
(3/8) ms
(1/8) μs
(3/8) μs
What does the term "Continuous Conduction Mode (CCM)" mean in the context of a
buck-boost converter?
The switch is always on
The diode is always conducting
The inductor current never drops to zero
The output voltage is always constant
What is the main disadvantage of a buck-boost converter?
Low efficiency at all operating points
Inverted output voltage polarity relative to the input
Complex control strategy
High component count
In a boost converter, what is the effect of operating in Discontinuous Conduction
Mode (DCM)?
The output voltage ripple decreases
The inductor current falls to zero during each cycle
The efficiency increases significantly
The output voltage becomes unregulated
