Q.1 What is the primary purpose of an inverter in power electronics?
Convert AC to DC
Convert DC to AC
Step down voltage
Step up voltage
Explanation - An inverter takes a DC input and produces an AC output suitable for powering AC loads or feeding the grid.
Correct answer is: Convert DC to AC
Q.2 Which switching device is most commonly used in modern inverters for high‑power applications?
Silicon diode
MOSFET
IGBT
Thyristor
Explanation - IGBTs combine the high‑speed switching of MOSFETs with the high‑current capability of bipolar transistors, making them ideal for high‑power inverters.
Correct answer is: IGBT
Q.3 In a half‑bridge inverter, what is the purpose of the center‑tap resistor?
To block DC voltage
To provide reference for PWM
To divide the supply voltage
To increase switching frequency
Explanation - The center‑tap resistor splits the DC bus voltage into two equal parts, providing symmetrical half‑bridge arms.
Correct answer is: To divide the supply voltage
Q.4 What does PWM stand for in inverter control?
Pulse Width Modulation
Phase Winding Modulation
Power Wave Modulation
Pulse Wavelength Modulation
Explanation - PWM is a technique that varies the width of voltage pulses to control the effective output voltage and frequency.
Correct answer is: Pulse Width Modulation
Q.5 Which of the following is NOT a type of PWM scheme?
Sinusoidal PWM
Space Vector PWM
Pulse Frequency Modulation
Sinusoidal PWM with Direct Voltage Mode
Explanation - PWM involves pulse width variation; pulse frequency modulation is a different concept used in some signal processing.
Correct answer is: Pulse Frequency Modulation
Q.6 Why is dead‑time introduced in inverter switching?
To increase switching speed
To prevent shoot‑through between high‑side and low‑side switches
To reduce the DC bus voltage
To improve the harmonic spectrum
Explanation - Dead‑time ensures that both switches in a bridge do not conduct simultaneously, avoiding a short circuit across the DC bus.
Correct answer is: To prevent shoot‑through between high‑side and low‑side switches
Q.7 Which parameter directly affects the output harmonic distortion of an inverter?
Switching frequency
DC bus voltage
Load resistance
Grounding method
Explanation - Higher switching frequencies allow a better approximation of the desired output waveform, reducing harmonics.
Correct answer is: Switching frequency
Q.8 What is the main advantage of a resonant inverter over a conventional square‑wave inverter?
Higher power factor
Simpler control circuitry
Higher efficiency at high frequencies
Lower component count
Explanation - Resonant inverters operate at the resonant frequency, reducing switching losses and improving efficiency.
Correct answer is: Higher efficiency at high frequencies
Q.9 In a multilevel inverter, how many voltage levels are produced with an N‑level design?
N
N+1
2N−1
2N
Explanation - An N‑level inverter using cascaded H‑bridges can produce 2N−1 discrete output voltage levels.
Correct answer is: 2N−1
Q.10 Which topology is commonly used for grid‑connected photovoltaic inverters?
Full‑bridge inverter
Half‑bridge inverter
Multilevel inverter
Half‑bridge plus DC‑link capacitor
Explanation - Half‑bridge inverters are compact and cost‑effective for the moderate power levels typical of solar PV systems.
Correct answer is: Half‑bridge inverter
Q.11 What does the term 'soft‑switching' refer to in the context of inverter design?
Switching at zero current
Switching at zero voltage
Using soft materials for switches
Using low‑frequency signals
Explanation - Soft‑switching techniques, like zero‑voltage switching (ZVS), reduce switching losses by turning on/off devices when voltage across them is zero.
Correct answer is: Switching at zero voltage
Q.12 What is the effect of increasing the DC bus voltage in an inverter on the output voltage?
Output voltage decreases
Output voltage remains the same
Output voltage increases
Output frequency changes
Explanation - The inverter’s output voltage scales proportionally with the DC bus voltage for a given modulation index.
Correct answer is: Output voltage increases
Q.13 Which of these is a common load for a power inverter?
A DC motor
A stepper motor
A resistive heater
A DC rectifier
Explanation - Resistive loads, such as heaters, are typical for power inverters, though inverters can also drive inductive loads.
Correct answer is: A resistive heater
Q.14 In a full‑bridge inverter, how many switches are required?
2
3
4
6
Explanation - A full‑bridge inverter uses four switches (two high‑side, two low‑side) to produce a bipolar output voltage.
Correct answer is: 4
Q.15 Which component is typically used to suppress voltage spikes during switching in inverters?
Snubber circuit
Heat sink
Capacitor bank
Inductor coil
Explanation - Snubber circuits dampen voltage transients caused by rapid switching, protecting the semiconductor devices.
Correct answer is: Snubber circuit
Q.16 What is the main function of the DC link capacitor in an inverter?
Store energy for smooth output
Reduce harmonic distortion
Limit current rise
Provide isolation from the grid
Explanation - The DC link capacitor supplies instantaneous current to the inverter and smooths the DC bus voltage during switching.
Correct answer is: Store energy for smooth output
Q.17 Which parameter is most critical when selecting an IGBT for an inverter application?
Gate charge
Breakdown voltage
Collector current rating
Package type
Explanation - The collector current rating ensures the IGBT can handle the maximum current demanded by the load.
Correct answer is: Collector current rating
Q.18 In a sinusoidal PWM inverter, what determines the number of harmonics present in the output waveform?
Switching frequency
Modulation index
Load impedance
DC bus voltage
Explanation - Higher switching frequencies push harmonics to higher frequencies, reducing their effect on the fundamental component.
Correct answer is: Switching frequency
Q.19 Which of the following is a common failure mode of MOSFETs in inverters?
Gate oxide breakdown
Thermal runaway
Gate leakage
Reverse breakdown
Explanation - Excessive voltage or current can damage the thin oxide layer, leading to MOSFET failure.
Correct answer is: Gate oxide breakdown
Q.20 What is the function of a soft‑switching technique like ZVS in resonant inverters?
Increase output voltage
Reduce switching losses
Lower the DC bus voltage
Improve torque in motors
Explanation - Zero‑voltage switching aligns transistor turn‑on with zero voltage, minimizing energy lost during switching.
Correct answer is: Reduce switching losses
Q.21 In a two‑level inverter, what is the maximum possible output voltage amplitude?
Half the DC bus voltage
Full DC bus voltage
Twice the DC bus voltage
Zero
Explanation - The output swings between ±Vdc/2 in a two‑level topology.
Correct answer is: Half the DC bus voltage
Q.22 What does the term 'duty cycle' refer to in PWM control?
The ratio of on-time to the switching period
The ratio of output voltage to DC bus voltage
The ratio of harmonic content to fundamental
The ratio of current to voltage
Explanation - Duty cycle determines the effective voltage level in PWM by controlling the proportion of time a switch is on.
Correct answer is: The ratio of on-time to the switching period
Q.23 Which of the following is a direct benefit of using a multilevel inverter?
Higher output current
Lower number of switches
Reduced harmonic distortion
Simpler control algorithm
Explanation - Multilevel topologies produce smoother waveforms, leading to lower total harmonic distortion.
Correct answer is: Reduced harmonic distortion
Q.24 Which parameter is most affected by the dead‑time delay in an inverter?
Switching losses
Output voltage ripple
Output frequency
DC bus voltage
Explanation - Increased dead‑time increases overlap periods where devices are partially on, raising switching losses.
Correct answer is: Switching losses
Q.25 What role does the gate driver play in inverter design?
Convert AC to DC
Supply gate voltage to switching devices
Measure output voltage
Control the load
Explanation - The gate driver provides the required voltage/current pulses to turn the MOSFETs/IGBTs on and off.
Correct answer is: Supply gate voltage to switching devices
Q.26 Which of the following is a typical output waveform for a three‑phase inverter?
Square wave
Triangular wave
Sine wave
Pulse wave
Explanation - Three‑phase inverters are designed to produce sinusoidal waveforms suitable for AC motors and grids.
Correct answer is: Sine wave
Q.27 In the context of inverters, what does the term 'overmodulation' mean?
Using a modulation index greater than 1
Using a modulation index less than 0.5
Operating at higher voltage
Operating at lower frequency
Explanation - Overmodulation occurs when the modulation index exceeds unity, causing waveform distortion and limiting maximum output voltage.
Correct answer is: Using a modulation index greater than 1
Q.28 Which of the following is a typical control objective in inverter design?
Minimize output voltage ripple
Maximize harmonic distortion
Reduce DC bus voltage
Increase switching frequency arbitrarily
Explanation - Control strategies aim to produce smooth output waveforms with minimal ripple and distortion.
Correct answer is: Minimize output voltage ripple
Q.29 What is the purpose of a DC‑link voltage regulator in an inverter?
To increase the switching frequency
To stabilize the DC bus voltage
To reduce the load impedance
To provide isolation from the grid
Explanation - A voltage regulator maintains a constant DC bus voltage despite load variations, improving inverter performance.
Correct answer is: To stabilize the DC bus voltage
Q.30 Which component is used to sense the load current in a current‑controlled inverter?
Hall‑effect sensor
Potentiometer
Thermistor
Capacitor
Explanation - Hall‑effect sensors provide non‑invasive current measurement for closed‑loop current control.
Correct answer is: Hall‑effect sensor
Q.31 What is the effect of increasing the switching frequency on the output voltage ripple?
Rises linearly
Decreases inversely
Remains unchanged
Becomes zero
Explanation - Higher switching frequencies shift ripple to higher frequencies, reducing its amplitude in the fundamental band.
Correct answer is: Decreases inversely
Q.32 Which of the following best describes a 'dead‑time insertion' strategy?
Adding a short delay between switch transitions
Increasing the switching frequency
Adding a DC‑link capacitor
Adding an inductor to the load
Explanation - Dead‑time insertion ensures that one switch is fully off before the other turns on, preventing shoot‑through.
Correct answer is: Adding a short delay between switch transitions
Q.33 In a resonant inverter, what role does the resonant tank play?
Store energy
Generate harmonics
Control switching
Set the operating frequency
Explanation - The resonant tank (inductor and capacitor) determines the natural frequency at which the inverter operates with minimal losses.
Correct answer is: Set the operating frequency
Q.34 Which of these parameters directly affects the switching losses in an IGBT?
Gate charge
Collector-emitter voltage
Emitter current
Package size
Explanation - Higher voltage across the IGBT during switching results in larger energy dissipated per cycle.
Correct answer is: Collector-emitter voltage
Q.35 What is the primary reason for using a soft‑switching inverter in a high‑efficiency application?
To increase harmonic distortion
To reduce switching losses
To increase output voltage
To simplify the control algorithm
Explanation - Soft‑switching techniques minimize energy dissipated during switching, boosting overall efficiency.
Correct answer is: To reduce switching losses
Q.36 Which component is essential for providing a low‑impedance path for high‑frequency currents in an inverter?
DC link capacitor
DC link inductor
Snubber capacitor
Snubber resistor
Explanation - The DC link inductor smooths high‑frequency currents and reduces voltage spikes.
Correct answer is: DC link inductor
Q.37 In a full‑bridge inverter, which switching pair is used to generate a positive half‑cycle?
Upper high‑side and lower low‑side
Both high‑side
Both low‑side
Upper low‑side and lower high‑side
Explanation - When the upper high‑side and lower low‑side switches conduct, the output is positive.
Correct answer is: Upper high‑side and lower low‑side
Q.38 What is the typical effect of increasing the DC link capacitor value?
Increase output voltage ripple
Decrease output voltage ripple
Increase switching frequency
Decrease switching frequency
Explanation - A larger capacitance stores more charge, reducing voltage fluctuations during switching.
Correct answer is: Decrease output voltage ripple
Q.39 Which of the following is NOT a typical output waveform for an inverter?
Square wave
Triangular wave
Sinusoidal wave
Sawtooth wave
Explanation - Inverters produce AC waveforms; triangular waves are not standard inverter outputs.
Correct answer is: Triangular wave
Q.40 In a grid‑connected inverter, what is the purpose of the DC‑link filter?
Reduce harmonics before feeding the grid
Store energy for load
Increase output voltage
Provide isolation between the inverter and the grid
Explanation - DC‑link filters smooth the DC bus and reduce high‑frequency content before AC output.
Correct answer is: Reduce harmonics before feeding the grid
Q.41 Which control strategy is commonly used to maintain a constant output voltage in a voltage‑source inverter?
Current‑mode control
Voltage‑mode control
PWM‑mode control
Frequency‑mode control
Explanation - Voltage‑mode control adjusts the duty cycle to keep the output voltage constant.
Correct answer is: Voltage‑mode control
Q.42 In a three‑phase inverter, what is the phase shift between the three output voltage waveforms?
45°
60°
90°
120°
Explanation - A three‑phase system has 120° phase separation between each phase.
Correct answer is: 120°
Q.43 Which of these is a disadvantage of a two‑level inverter?
High harmonic distortion
Complex control algorithm
High cost
Large number of switches
Explanation - Two‑level inverters produce more significant harmonics compared to multilevel designs.
Correct answer is: High harmonic distortion
Q.44 Which component is used to limit the peak current during inrush in a power inverter?
Current sense resistor
Inductor
Diode
Capacitor
Explanation - An inductor limits the rate of current increase, reducing inrush currents.
Correct answer is: Inductor
Q.45 What is the main function of the snubber in an inverter?
To provide isolation
To smooth the output voltage
To protect the switches from voltage spikes
To regulate the DC bus voltage
Explanation - The snubber absorbs transient voltages that could damage the semiconductor switches.
Correct answer is: To protect the switches from voltage spikes
Q.46 Which type of inverter topology can operate with a single DC source and produce a three‑phase AC output?
Half‑bridge
Full‑bridge
Three‑phase inverter
Single‑phase inverter
Explanation - A dedicated three‑phase inverter uses three H‑bridges driven from the same DC bus.
Correct answer is: Three‑phase inverter
Q.47 What is the purpose of the output filter in an inverter?
Reduce switching losses
Smooth the AC output waveform
Increase the DC bus voltage
Provide isolation
Explanation - Output filters remove high‑frequency switching harmonics to provide a clean sine wave.
Correct answer is: Smooth the AC output waveform
Q.48 In an inverter, what does the term 'duty cycle' directly influence?
Output frequency
Output voltage amplitude
Output current
Switching losses
Explanation - The duty cycle determines how much of the DC bus voltage appears at the output.
Correct answer is: Output voltage amplitude
Q.49 Which component provides the gate voltage required for switching MOSFETs?
Gate driver
Snubber circuit
DC link capacitor
Inductor
Explanation - The gate driver supplies the necessary voltage and current to turn MOSFETs on and off.
Correct answer is: Gate driver
Q.50 What is the main benefit of using an H‑bridge in inverter design?
Simplifies control
Reduces number of switches
Increases output voltage
Eliminates dead‑time
Explanation - An H‑bridge allows for easy inversion of output voltage polarity with a simple gate control scheme.
Correct answer is: Simplifies control
Q.51 In a resonant inverter, at what frequency does the inductor and capacitor resonate?
At the grid frequency
At the switching frequency
At the natural resonant frequency of the tank
At the harmonic frequency
Explanation - The resonant frequency is determined by the values of the inductor and capacitor in the resonant tank.
Correct answer is: At the natural resonant frequency of the tank
Q.52 Which of the following is NOT a type of PWM used in inverter control?
Sinusoidal PWM
Space‑vector PWM
Pulse‑frequency modulation
Phase‑shift PWM
Explanation - Pulse‑frequency modulation is not a standard PWM technique for inverters.
Correct answer is: Pulse‑frequency modulation
Q.53 Which factor primarily determines the thermal stress on a switching device?
Switching frequency
Switching voltage
Switching current
All of the above
Explanation - Thermal stress is influenced by voltage, current, and frequency of switching events.
Correct answer is: All of the above
Q.54 What is the typical operating frequency range for residential inverters?
50–60 Hz
20–40 kHz
100–200 kHz
1–2 MHz
Explanation - Residential inverters often use switching frequencies in the tens of kHz to achieve efficient operation.
Correct answer is: 20–40 kHz
Q.55 Which of these devices is most suitable for a 12 kW solar inverter?
Narrow‑band IGBTs
MOSFETs
IGBTs
Diodes
Explanation - IGBTs handle high currents and voltages required for a 12 kW solar inverter.
Correct answer is: IGBTs
Q.56 What does the term 'gate drive voltage' refer to?
Voltage across the drain and source
Voltage applied to the gate of a MOSFET/IGBT
Voltage of the DC bus
Voltage across the load
Explanation - Gate drive voltage is the control signal that turns the switch on or off.
Correct answer is: Voltage applied to the gate of a MOSFET/IGBT
Q.57 Which of the following is a characteristic of a soft‑switching inverter?
High switching losses
Low switching frequency
Zero‑voltage switching
High harmonic distortion
Explanation - Soft‑switching inverters use ZVS or ZCS to reduce switching losses and improve efficiency.
Correct answer is: Zero‑voltage switching
Q.58 In a voltage‑source inverter, what is the role of the DC bus voltage?
Set the output frequency
Provide the energy source
Control the output current
Determine the switching period
Explanation - The DC bus supplies the power that the inverter converts into AC output.
Correct answer is: Provide the energy source
Q.59 Which of the following is the main source of switching losses?
Gate resistance
Collector‑emitter voltage swing
Input capacitance
Inductor core losses
Explanation - The energy lost during a switch transition is proportional to the voltage swing across the device.
Correct answer is: Collector‑emitter voltage swing
Q.60 What is the effect of increasing the duty cycle beyond 100% in an inverter?
Increases output voltage further
Reduces output voltage
Causes overmodulation and distortion
Has no effect
Explanation - Duty cycles above 100% lead to overmodulation, distorting the waveform.
Correct answer is: Causes overmodulation and distortion
Q.61 In a three‑phase inverter, which phase leads the others by 120°?
Phase A
Phase B
Phase C
None of the above
Explanation - Conventionally, Phase A is considered the reference phase, with B and C following at 120° intervals.
Correct answer is: Phase A
Q.62 Which of the following is a common failure mode in MOSFETs due to high current?
Gate oxide breakdown
Drain‑to‑source breakdown
Source‑to‑bulk breakdown
Channel shorting
Explanation - Excessive voltage between drain and source can exceed the breakdown threshold, damaging the MOSFET.
Correct answer is: Drain‑to‑source breakdown
Q.63 What is the purpose of the DC‑link capacitor in an inverter?
Filter AC harmonics
Store energy to supply current during switching
Provide isolation
Control the switching frequency
Explanation - The capacitor delivers charge during the switching intervals to keep the DC bus voltage stable.
Correct answer is: Store energy to supply current during switching
Q.64 In a multilevel inverter, what is the typical switching frequency range?
10–20 kHz
20–60 kHz
60–200 kHz
200–400 kHz
Explanation - Multilevel inverters often operate in the tens of kHz range to maintain high efficiency.
Correct answer is: 20–60 kHz
Q.65 Which of the following is a key benefit of using IGBTs over MOSFETs in high‑voltage inverter applications?
Lower gate drive voltage
Higher switching frequency
Higher breakdown voltage
Lower conduction losses
Explanation - IGBTs can withstand higher voltages, making them suitable for high‑voltage inverters.
Correct answer is: Higher breakdown voltage
Q.66 What is the main disadvantage of using a zero‑voltage switching technique?
Higher switching losses
Complex control circuitry
Requirement for resonant tank
Increased output voltage ripple
Explanation - ZVS requires additional resonant components, increasing design complexity and cost.
Correct answer is: Requirement for resonant tank
Q.67 Which of the following best describes the function of a DC‑to‑AC inverter?
Convert AC to DC
Convert DC to AC
Convert DC to DC
Convert AC to AC
Explanation - An inverter takes DC power and outputs an AC waveform.
Correct answer is: Convert DC to AC
Q.68 Which component is used to provide a reference voltage for the gate of an IGBT in a half‑bridge inverter?
Voltage divider
Capacitor
Inductor
Resistor network
Explanation - A voltage divider provides the appropriate gate voltage relative to the DC bus.
Correct answer is: Voltage divider
Q.69 What is the purpose of a current‑sense resistor in an inverter controller?
Measure voltage
Measure current
Provide isolation
Control switching frequency
Explanation - The current‑sense resistor creates a voltage proportional to current, allowing feedback control.
Correct answer is: Measure current
Q.70 Which type of inverter is most suitable for high‑efficiency, low‑harmonic applications?
Resonant inverter
Resonant‑like inverter
Resonant‑plus inverter
Resonant‑plus‑like inverter
Explanation - Resonant inverters minimize switching losses and produce low harmonics.
Correct answer is: Resonant inverter
Q.71 In a half‑bridge inverter, what is the function of the freewheeling diode?
Conduct during positive half‑cycle
Conduct during negative half‑cycle
Provide isolation
Reduce switching losses
Explanation - The freewheeling diode allows the inductive load to circulate when the high‑side switch turns off.
Correct answer is: Conduct during positive half‑cycle
Q.72 Which parameter is most important in selecting a DC link capacitor for an inverter?
Capacitance value
Capacitance tolerance
Voltage rating
All of the above
Explanation - All listed parameters affect the capacitor’s suitability for the application.
Correct answer is: All of the above
Q.73 What does the term 'overvoltage protection' in inverter design refer to?
Protecting switches from overcurrent
Protecting switches from excessive voltage
Protecting the DC bus from over‑charging
Protecting the output from high voltage
Explanation - Overvoltage protection ensures semiconductor devices are not exposed to voltages beyond their ratings.
Correct answer is: Protecting switches from excessive voltage
Q.74 Which of the following is NOT a typical component in a voltage‑source inverter?
DC link capacitor
Gate driver
Load resistor
Control IC
Explanation - The load is external; the inverter contains internal components only.
Correct answer is: Load resistor
Q.75 What is the main purpose of a DC‑link inductor in an inverter?
Reduce current ripple
Provide isolation
Control the switching frequency
Increase output voltage
Explanation - The inductor smooths the high‑frequency current pulses from the switches.
Correct answer is: Reduce current ripple
Q.76 Which of the following is a common control method for a voltage‑source inverter?
Current mode control
Voltage mode control
Frequency mode control
Phase‑shift control
Explanation - Voltage‑mode control adjusts the duty cycle to maintain a desired output voltage.
Correct answer is: Voltage mode control
Q.77 Which of these is a typical application of a full‑bridge inverter?
Battery chargers
Solar inverters
AC motors
All of the above
Explanation - Full‑bridge inverters are versatile and used in many power conversion scenarios.
Correct answer is: All of the above
Q.78 Which of the following devices can be used to realize zero‑voltage switching?
Resonant inductor
Capacitor
Both A and B
None of the above
Explanation - Resonant tanks using inductors and capacitors enable ZVS operation.
Correct answer is: Both A and B
Q.79 What is the effect of increasing the load resistance on inverter efficiency?
Increases efficiency
Decreases efficiency
No effect
Depends on switching frequency
Explanation - Higher resistance reduces current, thereby reducing conduction losses.
Correct answer is: Increases efficiency
Q.80 Which of the following is a key benefit of using a three‑phase inverter?
Simpler control
Balanced power delivery
Lower component count
Higher harmonic content
Explanation - Three‑phase systems provide smooth power with lower torque ripple.
Correct answer is: Balanced power delivery
Q.81 What is the main disadvantage of using a full‑bridge inverter with a single DC bus?
Complex control scheme
Large voltage drop
High harmonic content
Requires two DC buses
Explanation - Full‑bridge inverters produce more significant harmonics compared to multilevel designs.
Correct answer is: High harmonic content
Q.82 Which component provides isolation between the DC input and the AC output?
Transformer
Capacitor
Inductor
Resistor
Explanation - A transformer offers galvanic isolation and voltage transformation between input and output.
Correct answer is: Transformer
Q.83 What does the term 'total harmonic distortion' (THD) measure?
The sum of all harmonic voltages
The ratio of harmonic power to fundamental power
The frequency of the fundamental component
The output voltage amplitude
Explanation - THD quantifies the deviation of a waveform from a pure sine wave.
Correct answer is: The ratio of harmonic power to fundamental power
Q.84 Which of the following is NOT a factor influencing the choice of switching frequency?
Desired efficiency
Load characteristics
Thermal constraints
Ambient temperature only
Explanation - While ambient temperature matters, other factors also dictate switching frequency.
Correct answer is: Ambient temperature only
Q.85 What is the purpose of a voltage‑feedback loop in an inverter?
Control the switching frequency
Control the output voltage level
Control the input voltage
Control the load impedance
Explanation - A voltage‑feedback loop adjusts the duty cycle to maintain the desired output voltage.
Correct answer is: Control the output voltage level
Q.86 What is the primary difference between a voltage‑source inverter and a current‑source inverter?
Operating frequency
Output voltage control
Switching devices used
Control strategy
Explanation - Voltage‑source inverters regulate voltage; current‑source inverters regulate current.
Correct answer is: Output voltage control
Q.87 In a half‑bridge inverter, which component is used to provide a reference voltage for the low‑side gate?
DC link capacitor
Voltage divider
Inductor
Snubber circuit
Explanation - The low‑side gate is referenced to a fraction of the DC bus via a voltage divider.
Correct answer is: Voltage divider
Q.88 Which of the following is a typical output waveform for a three‑phase inverter?
Single‑phase sine wave
Three‑phase sine waves
Square waves
Triangular wave
Explanation - A three‑phase inverter produces three sinusoidal outputs shifted by 120°.
Correct answer is: Three‑phase sine waves
Q.89 What does the term 'gate pulse width' refer to in inverter switching?
The width of the PWM signal
The width of the voltage pulse applied to the gate
The width of the current pulse
The width of the output voltage pulse
Explanation - Gate pulse width determines the on/off period of the switching device.
Correct answer is: The width of the voltage pulse applied to the gate
Q.90 Which of the following is a major disadvantage of a high‑frequency inverter?
Low efficiency
Large output filter size
Complex control
High switching losses
Explanation - Higher switching frequencies increase energy lost per switching event, reducing efficiency.
Correct answer is: High switching losses
Q.91 What is the role of the DC‑link capacitor in an inverter’s DC bus?
Provide isolation
Reduce voltage ripple
Increase switching speed
Control output frequency
Explanation - The capacitor smooths the DC bus, minimizing voltage ripple during switching.
Correct answer is: Reduce voltage ripple
Q.92 Which type of inverter topology uses a single DC input to produce a three‑phase AC output?
Half‑bridge
Full‑bridge
Three‑phase inverter
Resonant inverter
Explanation - A three‑phase inverter typically uses three H‑bridges driven from the same DC bus.
Correct answer is: Three‑phase inverter
Q.93 Which device is commonly used to protect against overvoltage in inverter design?
Fuse
Thyristor
Zener diode
MOSFET
Explanation - Zener diodes clamp voltage spikes, protecting sensitive components.
Correct answer is: Zener diode
Q.94 What is the typical duty cycle range for a sinusoidal PWM inverter?
0–0.5
0.5–1
0–1
1–2
Explanation - The duty cycle can vary from 0% (no conduction) to 100% (full conduction).
Correct answer is: 0–1
Q.95 Which of the following is a major benefit of using IGBTs in high‑power inverters?
Lower on‑resistance
Higher switching frequency
Higher voltage capability
Lower gate charge
Explanation - IGBTs can handle higher voltages than MOSFETs, making them suitable for high‑power applications.
Correct answer is: Higher voltage capability
Q.96 In a voltage‑source inverter, what does the duty cycle control?
Output voltage amplitude
Output frequency
Switching losses
Gate drive voltage
Explanation - Duty cycle directly determines the average voltage seen at the output.
Correct answer is: Output voltage amplitude
Q.97 Which of these is a common failure mode for MOSFETs due to overtemperature?
Gate oxide degradation
Shorted gate‑to‑source
Thickening of the body diode
Increased channel resistance
Explanation - Excess heat can damage the thin gate oxide layer, leading to device failure.
Correct answer is: Gate oxide degradation
Q.98 What is the purpose of a DC‑link filter in an inverter?
Smooth the DC bus voltage
Reduce output voltage ripple
Provide isolation
Control the switching frequency
Explanation - The DC‑link filter stabilizes the bus voltage during switching transients.
Correct answer is: Smooth the DC bus voltage
Q.99 Which of the following components is critical for protecting IGBTs from overcurrent?
Gate driver
Snubber circuit
Current sense resistor
Heat sink
Explanation - A current sense resistor provides feedback for overcurrent protection circuits.
Correct answer is: Current sense resistor
Q.100 In a resonant inverter, which element determines the resonant frequency?
Switching frequency
DC bus voltage
Resonant capacitor
Resonant inductor
Explanation - The resonant frequency depends on both the inductor and capacitor values in the tank.
Correct answer is: Resonant capacitor
Q.101 What is the main function of the output filter in an inverter?
Smooth the AC output waveform
Provide isolation
Store energy
Control switching frequency
Explanation - Output filters remove high‑frequency harmonics to deliver a cleaner sine wave.
Correct answer is: Smooth the AC output waveform
Q.102 Which of the following is a key benefit of using a full‑bridge inverter?
Lower component count
Higher output voltage swing
Simpler control
Lower efficiency
Explanation - A full‑bridge inverter can produce a full‑scale voltage swing of ±Vdc.
Correct answer is: Higher output voltage swing
Q.103 What is the typical operating frequency for a residential inverter?
50–60 Hz
1–10 kHz
20–30 kHz
100–200 kHz
Explanation - Residential inverters often use switching frequencies in the tens of kHz to balance efficiency and filter size.
Correct answer is: 20–30 kHz
Q.104 Which component is used to provide a high‑speed gate drive signal?
Gate driver IC
MOSFET
IGBT
Diode
Explanation - A dedicated gate driver provides the necessary voltage and current to switch devices quickly.
Correct answer is: Gate driver IC
Q.105 In a half‑bridge inverter, which switch is turned off during the negative half‑cycle?
High‑side switch
Low‑side switch
Both switches
Neither switch
Explanation - During the negative half‑cycle the high‑side switch is off and the low‑side switch conducts.
Correct answer is: High‑side switch
Q.106 Which of the following is a common type of resonant inverter?
Half‑bridge resonant inverter
Full‑bridge resonant inverter
Single‑phase resonant inverter
All of the above
Explanation - Resonant inverters can be designed in multiple bridge configurations.
Correct answer is: All of the above
Q.107 What is the effect of increasing the dead‑time on the output waveform?
Increases harmonic distortion
Decreases output voltage ripple
Increases switching losses
Reduces output frequency
Explanation - Longer dead‑time leads to overlap where devices partially conduct, increasing losses.
Correct answer is: Increases switching losses
Q.108 Which of these is a primary reason for using an IGBT instead of a MOSFET in a grid‑connected inverter?
Higher switching frequency
Higher current density
Higher voltage rating
Lower gate charge
Explanation - IGBTs can handle higher voltages, which is often required for grid‑connected systems.
Correct answer is: Higher voltage rating
Q.109 In a voltage‑source inverter, what is the purpose of the gate driver IC?
Provide isolation
Sense current
Generate gate drive pulses
Control output frequency
Explanation - The gate driver IC creates the voltage and current pulses needed to turn the switches on and off.
Correct answer is: Generate gate drive pulses
Q.110 What is the primary function of the DC link capacitor in an inverter?
Store energy for the load during switching
Provide isolation from the grid
Regulate the output voltage
Reduce the switching frequency
Explanation - The capacitor supplies current during the intervals between switch transitions.
Correct answer is: Store energy for the load during switching
Q.111 Which of the following best describes the operation of a half‑bridge inverter?
It uses two DC sources
It uses one DC source and two switches
It uses four switches in a bridge
It uses a transformer for isolation
Explanation - A half‑bridge inverter drives two switches with one DC bus to produce an AC output.
Correct answer is: It uses one DC source and two switches
Q.112 What is the effect of increasing the switching frequency on inverter efficiency?
Increases efficiency due to lower harmonic loss
Decreases efficiency due to higher switching loss
No effect
Depends on the load
Explanation - Higher switching frequency increases switching energy loss per cycle.
Correct answer is: Decreases efficiency due to higher switching loss
Q.113 Which component protects the switching device from reverse voltage during the off state?
Snubber diode
Flyback diode
Gate driver
Inductor
Explanation - The flyback diode provides a path for inductive currents when the switch turns off.
Correct answer is: Flyback diode
Q.114 What does the 'dead‑time' value determine in an inverter?
Switching speed
Duration between the turn‑off of one switch and the turn‑on of its complement
Output voltage amplitude
Switching frequency
Explanation - Dead‑time ensures one switch is fully off before its complementary switch turns on.
Correct answer is: Duration between the turn‑off of one switch and the turn‑on of its complement
Q.115 What is the main purpose of a resonant tank in a resonant inverter?
Increase output voltage
Provide zero‑voltage switching
Control the switching frequency
Reduce component count
Explanation - The resonant tank allows the inverter to operate with minimal voltage across the switching devices.
Correct answer is: Provide zero‑voltage switching
Q.116 Which of the following is a common failure mode of IGBTs?
Gate oxide breakdown
Latch‑up due to high current
Capacitance drift
Thermal runaway
Explanation - IGBTs can latch up if the base/emitter and base/collector junctions are simultaneously forward biased.
Correct answer is: Latch‑up due to high current
Q.117 Which of the following best describes a half‑bridge inverter?
It uses one DC source and two switches
It uses two DC sources and two switches
It uses four switches in a bridge configuration
It uses a transformer to isolate DC and AC
Explanation - A half‑bridge inverter employs two switches across a single DC bus to generate AC voltage.
Correct answer is: It uses one DC source and two switches
Q.118 Which of the following devices is typically used to clamp the voltage spikes in an inverter circuit?
Zener diode
Flyback diode
Inductor
Resistor
Explanation - Zener diodes clamp excessive voltage, protecting sensitive components.
Correct answer is: Zener diode
Q.119 What is the effect of increasing the DC link voltage on the inverter’s output voltage swing?
Increases output voltage swing
Decreases output voltage swing
No effect
Depends on load
Explanation - The output voltage swing is directly proportional to the DC link voltage.
Correct answer is: Increases output voltage swing
Q.120 Which component provides a reference voltage for the low‑side gate in a half‑bridge inverter?
Voltage divider
Inductor
Snubber circuit
Capacitor
Explanation - The voltage divider supplies a reference voltage to the gate of the low‑side switch.
Correct answer is: Voltage divider
Q.121 Which of the following is a major challenge in designing high‑frequency inverters?
Managing heat dissipation
Implementing low‑loss switches
Providing isolation
All of the above
Explanation - High‑frequency operation leads to increased switching losses, thermal management issues, and isolation challenges.
Correct answer is: All of the above
Q.122 Which of the following is a typical application of a full‑bridge inverter?
Battery chargers
Solar inverters
AC motors
All of the above
Explanation - Full‑bridge inverters are versatile and used in many power conversion applications.
Correct answer is: All of the above
Q.123 What does the 'switching frequency' of an inverter refer to?
The rate at which the output frequency changes
The frequency at which the switching devices are turned on and off
The frequency of the AC load
The frequency of the DC source
Explanation - Switching frequency is the rate at which the inverter’s switches are toggled.
Correct answer is: The frequency at which the switching devices are turned on and off
Q.124 Which of the following is an advantage of using a multilevel inverter?
Reduced component count
Higher switching frequency
Reduced harmonic content
Simpler control
Explanation - Multilevel topologies generate smoother waveforms, decreasing total harmonic distortion.
Correct answer is: Reduced harmonic content
Q.125 In a half‑bridge inverter, which switch is used to produce a positive half‑cycle?
High‑side switch
Low‑side switch
Both switches
Neither switch
Explanation - When the high‑side switch conducts and the low‑side is off, the output is positive.
Correct answer is: High‑side switch
Q.126 What is the purpose of the output filter in an inverter?
Reduce switching losses
Smooth the AC output waveform
Provide isolation
Control the switching frequency
Explanation - Output filters remove high‑frequency components from the inverter output.
Correct answer is: Smooth the AC output waveform
Q.127 Which of the following is a typical output waveform for a three‑phase inverter?
Single‑phase sine wave
Three‑phase sine waves
Square waves
Triangular wave
Explanation - A three‑phase inverter produces sinusoidal outputs for each phase.
Correct answer is: Three‑phase sine waves
Q.128 What does the term 'dead‑time' prevent in an inverter?
Shoot‑through between high‑side and low‑side switches
Voltage drop
Harmonic distortion
Switching losses
Explanation - Dead‑time ensures one switch is off before its complementary switch turns on.
Correct answer is: Shoot‑through between high‑side and low‑side switches
Q.129 Which of the following is a common method to reduce switching losses in high‑frequency inverters?
Use of snubber circuits
Use of resonant or soft‑switching techniques
Increase the DC bus voltage
Use of larger inductors
Explanation - Resonant and soft‑switching methods minimize energy dissipated during each transition.
Correct answer is: Use of resonant or soft‑switching techniques
Q.130 In a full‑bridge inverter, which pair of switches produce a negative half‑cycle?
Both high‑side switches
Both low‑side switches
Upper high‑side and lower low‑side
Upper low‑side and lower high‑side
Explanation - When these two switches conduct, the output is negative.
Correct answer is: Upper low‑side and lower high‑side
Q.131 What is the main advantage of a resonant inverter over a conventional inverter?
Higher efficiency at high frequencies
Lower component count
Simpler control scheme
Lower harmonic content
Explanation - Resonant inverters reduce switching losses by operating at their natural resonance.
Correct answer is: Higher efficiency at high frequencies
Q.132 Which of the following is a typical output waveform for a half‑bridge inverter?
Sine wave
Square wave
Triangular wave
Sawtooth wave
Explanation - A half‑bridge inverter outputs a square waveform that is then filtered to produce a sine wave.
Correct answer is: Square wave
Q.133 Which device is most suitable for high‑frequency switching in inverters?
IGBT
MOSFET
Thyristor
Diode
Explanation - MOSFETs have lower gate charge and can switch faster than IGBTs.
Correct answer is: MOSFET
Q.134 Which of the following is a typical control strategy used in a voltage‑source inverter?
Current mode control
Voltage mode control
Frequency mode control
Phase mode control
Explanation - Voltage‑mode control adjusts the duty cycle to regulate output voltage.
Correct answer is: Voltage mode control
Q.135 Which of the following best describes a resonant inverter?
An inverter that operates at the resonant frequency of a tank circuit
An inverter that uses a resonator to reduce output voltage
An inverter that operates at low frequencies
An inverter that uses a resonator to increase current
Explanation - Resonant inverters use a resonant tank to achieve zero‑voltage switching.
Correct answer is: An inverter that operates at the resonant frequency of a tank circuit
Q.136 What is the effect of increasing the switching frequency on the output harmonic spectrum?
Harmonics shift to higher frequencies
Harmonic content increases
Harmonic content decreases
No effect
Explanation - Higher switching frequencies push harmonics further away from the fundamental.
Correct answer is: Harmonics shift to higher frequencies
Q.137 Which component provides isolation between the DC source and the AC load in an inverter?
Capacitor
Transformer
Inductor
Resistor
Explanation - A transformer offers galvanic isolation and voltage transformation.
Correct answer is: Transformer
Q.138 Which of the following is a benefit of using a half‑bridge inverter with a single DC bus?
Reduced component count
Simplified control
Higher output voltage swing
All of the above
Explanation - The half‑bridge topology uses fewer components and provides a simpler design.
Correct answer is: All of the above
Q.139 Which of the following best describes the main function of an IGBT?
Switching at high voltage and current with moderate speed
High‑speed switching at low voltage
High current conduction without switching
Passive rectification
Explanation - IGBTs combine the high‑voltage capability of bipolar transistors with the fast switching of MOSFETs.
Correct answer is: Switching at high voltage and current with moderate speed