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WorksheetsPOWER ELECTRONICS_UNIT_V_DC-AC Converters_Day-Day Assessment
Total questions: 30
Worksheet time: 15mins
What is the primary function of a DC-AC converter?
To amplify direct current (DC) signals.
To convert direct current (DC) into alternating current (AC).
To convert alternating current (AC) into direct current (DC).
To store energy in a battery.
Name two common types of DC-AC converters.
Hybrid inverter
Transformer inverter
Square wave inverter, Sine wave inverter
Pulse width modulation inverter
What is the role of an inverter in a DC-AC converter?
To convert AC back into DC
To regulate voltage levels in a circuit
To store energy for later use
The role of an inverter in a DC-AC converter is to convert direct current (DC) into alternating current (AC).
How does a PWM (Pulse Width Modulation) technique work in DC-AC conversion?
PWM modulates the duty cycle of pulses to create an AC waveform from a DC source.
PWM converts AC signals into DC by filtering the waveform.
PWM uses a constant frequency to maintain a steady DC output.
PWM increases the voltage level of DC directly to AC.
What are the advantages of using a DC-AC converter in renewable energy systems?
Increased carbon emissions
Higher installation costs
The advantages of using a DC-AC converter in renewable energy systems include enabling grid compatibility, improving energy efficiency, and facilitating the use of energy storage.
Reduced energy output
Explain the difference between a full-bridge and half-bridge inverter.
A full-bridge inverter is more efficient than a half-bridge inverter.
A full-bridge inverter can produce both positive and negative output voltages, while a half-bridge inverter can only produce positive and zero voltages.
A half-bridge inverter can produce both positive and negative output voltages.
A full-bridge inverter requires fewer components than a half-bridge inverter.
What is the significance of the output waveform in DC-AC conversion?
The output waveform defines the quality and characteristics of the AC signal produced from a DC source.
The output waveform determines the efficiency of the DC source.
The output waveform only affects the input DC voltage.
The output waveform is irrelevant in DC-AC conversion.
How do you calculate the efficiency of a DC-AC converter?
Efficiency (%) = (Output Power / Input Power) x 100
Efficiency (%) = (Input Power / Output Power) x 100
Efficiency (%) = (Output Power + Input Power) x 100
Efficiency (%) = (Output Power - Input Power) x 100
What are the typical applications of DC-AC converters?
Industrial heating systems
Television broadcasting
Renewable energy systems, uninterruptible power supplies (UPS), electric vehicles, and motor drives.
Home appliances
What safety precautions should be taken when working with DC-AC converters?
Ensure proper grounding, use insulated tools, wear PPE, follow lockout/tagout procedures, and avoid working on live circuits.
Use metal tools for better conductivity
Work on live circuits for efficiency
Ignore PPE if the task seems simple
Switches used in VSI are ___________
Unipolar & Unidirectional
Bipolar & Bidirectional
Unipolar & Bidirectional
Unidirectional
Full form of VSI is ___________
Voltage source inverter
Volume source inverter
Voltage severe inverter
Voltage source inserter
Number of switches turned on in 3-phase 180° VSI at a single time are __________
3
2
1
4
Number of switches turned on in 3-phase 120° VSI at a single time are __________
2
4
5
3
T.H.D value for 3-∅ 180° VSI is ________________
36%
31%
39%
46%
Short circuit problem is severe in case of Voltage source inverter.
True
False
Inverters are used to convert DC power into variable AC power.
True
False
Line-commutated inverters have
AC on the supply side and DC on the load side
AC on both supply and load side
DC on both supply and load side
DC on the supply side and AC on the load side
In a VSI (Voltage source inverter)
the internal impedance of the DC source is negligible
the internal impedance of the DC source is very very high
the internal impedance of the AC source is negligible
the IGBTs are fired at 0 degrees.
VSIs using IGBTs are turned off by
load commutation
line commutation
applying a negative gate pulse
removing the base signal
__________ based inverters do not require self-commutation.
IGBT
GTO
PMOSFET
SCR
Single phase half bridge inverters requires
two wire ac supply
two wire dc supply
three wire ac supply
three wire dc supply
In a single-phase half wave inverter ________ SCR(s) are/is gated at a time.
1
2
3
None of the mentioned
The voltage in a single phase half wave inverter varies between
Vs and 0
Vs/2 and 0
Vs/2 and –Vs/2
Vs and –Vs
The output of a single-phase half bridge inverter on R load is ideally
a sine wave
a square wave
a triangular wave
constant dc
The output current wave of a single-phase full bridge inverter on RL load is
a sine wave
a square wave
a triangular wave
constant dc
The output voltage from a single phase full wave bridge inverter varies from
Vs to –Vs
Vs to zero
Vs/2 to zero
–Vs/2 to Vs/2
The fundamental component of output voltage for a half wave bridge inverter is given by
(4Vs/π) sinωt
(2Vs/π) sinωt
(Vs/2π) sinωt
(Vs)
A single phase half bridge inverter has a dc voltage source Vs/2 = 115 V. Find the rms value of the fundamental component of output voltage.
510V
103.5V
120V
96V
A single phase full bridge inverter has a dc voltage source Vs = 230 V. Find the rms value of the fundamental component of output voltage.
90V
207V
350V
196V
