Q.1 Which power electronic device is most commonly used in a three‑phase inverter for solar photovoltaic (PV) systems?
IGBT
Thyristor
Diode bridge
MOSFET
Explanation - IGBTs combine high voltage capability with fast switching, making them ideal for three‑phase inverters in PV applications.
Correct answer is: IGBT
Q.2 In an electric vehicle (EV) traction drive, the device that converts the battery DC voltage to variable‑frequency AC for the motor is called:
DC‑DC converter
DC‑AC inverter
Rectifier
Chopper
Explanation - The inverter changes the fixed DC battery voltage into a controllable AC voltage to drive the motor at different speeds.
Correct answer is: DC‑AC inverter
Q.3 Which of the following is a primary application of a DC‑DC buck converter in power electronics?
Step‑up voltage for LED drivers
Step‑down voltage for microcontroller supplies
Convert AC to DC
Generate three‑phase AC
Explanation - A buck converter reduces a higher DC voltage to a lower level, often used to power low‑voltage digital circuits.
Correct answer is: Step‑down voltage for microcontroller supplies
Q.4 Which power electronic topology is typically used in high‑power HVDC transmission systems?
Voltage‑source converter (VSC)
Current‑source converter (CSC)
Phase‑controlled rectifier
Full‑bridge diode rectifier
Explanation - VSCs allow independent control of voltage magnitude and phase angle, making them suitable for HVDC links.
Correct answer is: Voltage‑source converter (VSC)
Q.5 A variable‑frequency drive (VFD) for an AC induction motor primarily uses which two power electronic stages?
Rectifier and inverter
Chopper and boost converter
Buck converter and boost converter
Flyback and forward converter
Explanation - The VFD first rectifies the incoming AC to DC, then inverts it to AC with variable frequency and voltage.
Correct answer is: Rectifier and inverter
Q.6 In a renewable‑energy wind turbine system, the power electronic converter that connects the generator to the grid is called:
DC‑DC buck converter
DC‑AC inverter
AC‑DC rectifier
Phase‑controlled rectifier
Explanation - Most modern wind turbines generate variable‑frequency AC that is first rectified to DC and then inverted to match grid standards.
Correct answer is: DC‑AC inverter
Q.7 Which of the following devices is most suitable for high‑frequency switching in a Class‑D audio amplifier?
IGBT
MOSFET
Thyristor
Silicon‑controlled rectifier (SCR)
Explanation - MOSFETs have low on‑resistance and can switch at tens to hundreds of kilohertz, ideal for Class‑D audio.
Correct answer is: MOSFET
Q.8 A three‑phase diode bridge rectifier is used in which type of application?
Regenerative braking in EVs
Grid‑connected solar inverter
Uninterruptible Power Supply (UPS) input stage
Motor speed control
Explanation - UPS systems often use a diode bridge to convert AC mains to DC for battery charging and inverter operation.
Correct answer is: Uninterruptible Power Supply (UPS) input stage
Q.9 What is the main advantage of using a multilevel inverter in medium‑voltage motor drives?
Lower switching losses
Higher output voltage steps with reduced harmonic distortion
Simpler control algorithm
Reduced number of power devices
Explanation - Multilevel inverters produce output waveforms with many voltage steps, reducing total harmonic distortion and improving power quality.
Correct answer is: Higher output voltage steps with reduced harmonic distortion
Q.10 In a switched‑mode power supply (SMPS), which component stores energy during the on‑time of the switch?
Transformer
Capacitor
Inductor
Resistor
Explanation - During the switch on‑time, the inductor stores magnetic energy which is released when the switch turns off.
Correct answer is: Inductor
Q.11 Which power electronic converter is used to step up the voltage from a solar panel array before feeding it to the grid?
Boost converter
Buck converter
Buck‑boost converter
Flyback converter
Explanation - A boost converter raises the DC voltage from the PV array to the required level for the inverter or grid connection.
Correct answer is: Boost converter
Q.12 In an induction heating system, the power electronic switch must be able to operate at:
Low frequency (50 Hz)
Medium frequency (1 kHz)
High frequency (20 kHz–100 kHz)
DC
Explanation - Induction heating uses high‑frequency currents to generate eddy currents in the workpiece, requiring fast switching devices.
Correct answer is: High frequency (20 kHz–100 kHz)
Q.13 Which power electronic device is most often used in a high‑power electric locomotive for traction control?
MOSFET
IGBT
Thyristor
SCR
Explanation - IGBTs handle high voltages and currents with fast switching, suitable for locomotive traction inverters.
Correct answer is: IGBT
Q.14 A diode‑clamped multilevel inverter reduces the number of required power devices compared to a cascaded H‑bridge inverter because it:
Uses capacitors as voltage sources
Eliminates the need for a transformer
Shares devices among voltage levels
Operates at a lower switching frequency
Explanation - Diode‑clamped topologies use capacitors to create intermediate voltage levels, reducing the total count of active switches.
Correct answer is: Uses capacitors as voltage sources
Q.15 Which of the following is a key benefit of using power electronics in renewable energy systems?
Increasing mechanical wear
Enabling maximum power point tracking (MPPT)
Reducing system cost by removing converters
Eliminating need for storage
Explanation - Power electronic converters allow MPPT algorithms to extract the maximum possible power from solar or wind sources.
Correct answer is: Enabling maximum power point tracking (MPPT)
Q.16 In a DC‑fast charger for electric vehicles, the power stage typically uses which topology?
Phase‑controlled rectifier
Full‑bridge inverter
Bidirectional DC‑DC converter
Flyback converter
Explanation - Fast chargers require a bidirectional converter to control high current flow from the grid to the vehicle battery.
Correct answer is: Bidirectional DC‑DC converter
Q.17 Which converter type is most appropriate for supplying a constant voltage to a battery pack from a variable solar panel output?
Buck‑boost converter
Buck converter
Boost converter
Cuk converter
Explanation - A buck‑boost converter can step voltage up or down, maintaining a stable output despite varying input from the PV panel.
Correct answer is: Buck‑boost converter
Q.18 In a grid‑connected inverter, the function of the filter placed after the inverter is to:
Increase switching frequency
Reduce output voltage ripple and harmonics
Step up the voltage
Rectify the AC output
Explanation - LC or LCL filters smooth the inverter output, ensuring compliance with grid standards for harmonic distortion.
Correct answer is: Reduce output voltage ripple and harmonics
Q.19 Which of the following power electronic applications uses a resonant converter for efficient energy transfer?
LED driver
Battery charger
Induction heating
Uninterruptible Power Supply (UPS)
Explanation - Resonant converters operate at the resonant frequency of the load, minimizing switching losses in induction heating.
Correct answer is: Induction heating
Q.20 The primary advantage of using silicon‑carbide (SiC) MOSFETs over silicon IGBTs in high‑frequency converters is:
Lower cost
Higher blocking voltage
Lower switching losses at high frequency
Simpler gate drive
Explanation - SiC devices can switch faster with less loss, enabling higher frequency operation and smaller passive components.
Correct answer is: Lower switching losses at high frequency
Q.21 In a three‑phase motor drive, the term "field‑oriented control" (FOC) primarily relies on:
Precise current regulation using PWM inverters
Voltage regulation using linear regulators
Frequency modulation without current feedback
Mechanical sensor feedback
Explanation - FOC uses PWM‑controlled inverters to regulate stator currents to produce a rotating magnetic field aligned with the rotor.
Correct answer is: Precise current regulation using PWM inverters
Q.22 A buck‑boost converter can provide a negative output voltage relative to its input. Which application commonly uses this feature?
Battery charger
Audio amplifier
Op‑amp power supply
Solar inverter
Explanation - Many operational amplifiers require both positive and negative supply rails; a buck‑boost can generate the negative rail.
Correct answer is: Op‑amp power supply
Q.23 Which power electronic topology is best suited for low‑power (<10 W) isolated DC‑DC conversion?
Flyback converter
Forward converter
Half‑bridge converter
Full‑bridge converter
Explanation - Flyback converters provide isolation and are simple and cost‑effective for low‑power applications.
Correct answer is: Flyback converter
Q.24 In a three‑level neutral‑point‑clamped (NPC) inverter, the neutral point is kept balanced using:
Active power balancing control
Passive resistors only
Capacitor charging circuits
External DC link
Explanation - NPC inverters require active control strategies to maintain equal voltage across the split DC‑link capacitors.
Correct answer is: Active power balancing control
Q.25 Which of the following is NOT a typical function of power electronics in a hybrid electric vehicle (HEV)?
Battery charging
Motor drive control
Fuel injection timing
Regenerative braking energy recovery
Explanation - Fuel injection timing is managed by the engine control unit, not directly by power electronic converters.
Correct answer is: Fuel injection timing
Q.26 A Class‑E resonant converter is primarily used for:
Low‑frequency power supplies
High‑efficiency RF power generation
Battery charging
Motor speed control
Explanation - Class‑E resonant converters achieve high efficiency at radio frequencies, useful in RF transmitters and wireless power.
Correct answer is: High‑efficiency RF power generation
Q.27 Which component is essential for providing isolation in a DC‑DC converter used for medical equipment?
Transformer
Inductor
Capacitor
Diode
Explanation - Isolation transformers separate patient‑connected circuits from mains, ensuring safety in medical devices.
Correct answer is: Transformer
Q.28 In a high‑power LED driver, the current regulation is typically performed by:
Voltage‑mode control
Current‑mode PWM control
Frequency modulation
Resistive drop
Explanation - LED brightness depends on current; PWM current‑mode control maintains constant LED current while adjusting duty cycle.
Correct answer is: Current‑mode PWM control
Q.29 Which power electronic converter is used to step up a low voltage DC from a fuel cell to a higher DC bus voltage?
Buck converter
Boost converter
Buck‑boost converter
Cuk converter
Explanation - A boost converter raises the low fuel‑cell voltage to the required bus level for subsequent conversion stages.
Correct answer is: Boost converter
Q.30 In a railway traction system, the primary power electronic converter used to supply the AC traction motor is:
Three‑phase rectifier
Inverter
DC‑DC buck converter
Phase‑controlled thyristor bridge
Explanation - Inverters convert the DC link voltage (often from overhead lines) to variable‑frequency AC for the traction motor.
Correct answer is: Inverter
Q.31 A pulse‑width modulation (PWM) technique that reduces harmonic content by switching at the carrier frequency's zero crossing is called:
Sinusoidal PWM
Space vector PWM
Phase‑shifted PWM
Discontinuous PWM
Explanation - Space vector PWM selects switching vectors that minimize harmonic distortion and improve voltage utilization.
Correct answer is: Space vector PWM
Q.32 Which power electronic device is typically used for high‑current, low‑voltage applications such as welding?
MOSFET
IGBT
Thyristor
SCR
Explanation - Thyristors handle high currents and can be phase‑controlled, making them suitable for welding power supplies.
Correct answer is: Thyristor
Q.33 A three‑phase matrix converter provides which of the following advantages over traditional AC‑DC‑AC conversion?
Higher efficiency and bidirectional power flow without a DC link
Simpler control algorithm
Lower cost due to fewer components
Higher output voltage
Explanation - Matrix converters directly convert AC to AC, eliminating the DC link and enabling bidirectional operation.
Correct answer is: Higher efficiency and bidirectional power flow without a DC link
Q.34 In a photovoltaic (PV) system, the term "grid‑forming inverter" refers to:
An inverter that only injects power when grid voltage exists
An inverter that can create a stable voltage and frequency without a grid
A DC‑DC boost converter
A passive filter
Explanation - Grid‑forming (or grid‑forming) inverters act as a virtual grid, supplying voltage and frequency independently.
Correct answer is: An inverter that can create a stable voltage and frequency without a grid
Q.35 Which of the following is the most common topology for a high‑power DC‑fast charger (≥150 kW)?
Two‑stage AC‑DC‑DC converter
Single‑stage AC‑DC‑DC‑DC converter
Three‑stage AC‑DC‑DC‑DC‑DC converter
Direct AC‑AC converter
Explanation - A two‑stage approach (rectifier then high‑power DC‑DC) balances efficiency and control complexity for fast chargers.
Correct answer is: Two‑stage AC‑DC‑DC converter
Q.36 In a power factor correction (PFC) circuit for a SMPS, the objective is to:
Increase output voltage
Reduce input current ripple
Maintain input current in phase with input voltage
Eliminate the need for a filter
Explanation - PFC improves the power factor by shaping the input current waveform to follow the voltage waveform.
Correct answer is: Maintain input current in phase with input voltage
Q.37 Which converter topology is most appropriate for a low‑power (≤5 W) isolated DC‑DC supply in a sensor node?
Flyback converter
Forward converter
Push‑pull converter
Half‑bridge converter
Explanation - Flyback converters are simple, cost‑effective, and provide isolation for low‑power applications.
Correct answer is: Flyback converter
Q.38 In a high‑frequency induction furnace, the power electronic switch must have:
Low voltage rating
High current rating only
Both high voltage and high current ratings with fast switching
Only DC capability
Explanation - Induction furnaces operate at high currents and voltages with rapid switching to generate the required magnetic field.
Correct answer is: Both high voltage and high current ratings with fast switching
Q.39 What is the main purpose of a snubber circuit across a switching device in a power converter?
Increase switching speed
Limit voltage spikes and dissipate energy
Provide isolation
Regulate output voltage
Explanation - Snubbers protect switching devices from over‑voltage caused by parasitic inductance during turn‑off.
Correct answer is: Limit voltage spikes and dissipate energy
Q.40 A buck‑boost converter operating in continuous conduction mode (CCM) has a voltage conversion ratio of:
Vout/Vin = D
Vout/Vin = 1‑D
Vout/Vin = D/(1‑D)
Vout/Vin = (1‑D)/D
Explanation - In CCM, the buck‑boost converter’s voltage ratio is D/(1‑D), where D is the duty cycle.
Correct answer is: Vout/Vin = D/(1‑D)
Q.41 Which of the following statements about SiC devices compared to Si devices is FALSE?
SiC devices have higher thermal conductivity
SiC devices can operate at higher temperatures
SiC devices have lower on‑resistance for the same voltage rating
SiC devices always have lower cost than Si devices
Explanation - While SiC offers performance benefits, it is currently more expensive than traditional silicon devices.
Correct answer is: SiC devices always have lower cost than Si devices
Q.42 In a three‑phase active front‑end (AFE) rectifier used in motor drives, the main advantage over a diode bridge is:
Reduced cost
Bidirectional power flow and power factor correction
Higher voltage rating
Simpler control
Explanation - AFEs can control input current shape and allow power to flow back to the grid or source.
Correct answer is: Bidirectional power flow and power factor correction
Q.43 A power electronic converter that can operate both as a buck and a boost converter is known as:
Cuk converter
SEPIC converter
Buck‑boost converter
Flyback converter
Explanation - Buck‑boost converters provide both step‑down and step‑up voltage conversion capabilities.
Correct answer is: Buck‑boost converter
Q.44 Which power electronic application is most associated with the term "soft‑switching"?
Resistive heating
Induction motor drives
Resonant converters
Linear regulators
Explanation - Resonant converters achieve soft switching, reducing switching losses and electromagnetic interference.
Correct answer is: Resonant converters
Q.45 In a grid‑connected wind turbine with a permanent magnet synchronous generator (PMSG), the power electronic converter must:
Provide variable frequency to match grid frequency
Maintain constant DC link voltage only
Only rectify the generator output
Eliminate need for pitch control
Explanation - The inverter must adjust frequency and voltage to synchronize with the grid despite varying rotor speed.
Correct answer is: Provide variable frequency to match grid frequency
Q.46 A common method to achieve isolation in a high‑frequency SMPS is:
Using a large electrolytic capacitor
Employing a magnetic transformer
Adding a resistive divider
Using a voltage regulator IC
Explanation - High‑frequency transformers provide galvanic isolation while transferring energy efficiently.
Correct answer is: Employing a magnetic transformer
Q.47 Which of the following is an advantage of using a full‑bridge topology in a DC‑AC inverter for high‑power applications?
Lower number of switches
Ability to generate both positive and negative output voltages
Simpler gate driver circuitry
Reduced switching losses
Explanation - A full‑bridge inverter can produce a bipolar output, essential for many AC applications.
Correct answer is: Ability to generate both positive and negative output voltages
Q.48 In a battery management system (BMS), the role of the DC‑DC converter is to:
Charge the battery directly from the grid
Provide isolated power to the control electronics and balance cells
Increase the battery voltage for the motor
Regulate the motor speed
Explanation - The DC‑DC converter supplies low‑voltage power to BMS circuitry and can be used for cell balancing.
Correct answer is: Provide isolated power to the control electronics and balance cells
Q.49 Which power electronic device is typically used for high‑speed, low‑voltage switching in modern smartphones?
IGBT
MOSFET
Thyristor
SCR
Explanation - MOSFETs offer low on‑resistance and fast switching suitable for the low‑voltage power management of smartphones.
Correct answer is: MOSFET
Q.50 In a three‑phase diode bridge rectifier, the input current waveform is:
Sinusoidal and in phase with voltage
Pulsating and non‑sinusoidal
Constant DC
Zero
Explanation - Without filtering or power factor correction, the rectifier draws a pulsating current from the AC source.
Correct answer is: Pulsating and non‑sinusoidal
Q.51 The term "Maximum Power Point Tracking" (MPPT) is most closely associated with which application?
Wind turbine generators
Solar photovoltaic inverters
Battery chargers
LED drivers
Explanation - MPPT algorithms continuously adjust the operating point of a PV array to extract maximum power.
Correct answer is: Solar photovoltaic inverters
Q.52 Which of the following power electronic converters is typically used in a high‑power DC distribution system for voltage regulation?
Buck converter
Boost converter
Cuk converter
Bidirectional DC‑DC converter
Explanation - Bidirectional converters can both step up/down voltage and enable power flow in either direction, useful in DC grids.
Correct answer is: Bidirectional DC‑DC converter
Q.53 In a power electronic system, the term "dead‑time" refers to:
The time the system is idle between cycles
A short period when both high‑side and low‑side switches are off to prevent shoot‑through
The time required for a transformer to magnetize
The duration of the PWM carrier signal
Explanation - Dead‑time prevents simultaneous conduction of complementary switches, avoiding a short circuit.
Correct answer is: A short period when both high‑side and low‑side switches are off to prevent shoot‑through
Q.54 Which topology is used in many high‑efficiency LED drivers to achieve both step‑up and step‑down voltage conversion?
Buck converter
Boost converter
Buck‑boost converter
Cuk converter
Explanation - Buck‑boost converters can adapt to varying input voltages while delivering a constant LED current.
Correct answer is: Buck‑boost converter
Q.55 A power electronic system for electric aircraft propulsion must primarily focus on:
Low cost only
High efficiency and lightweight
High voltage only
Maximum current rating
Explanation - Weight and efficiency critically impact aircraft performance and range, making lightweight high‑efficiency converters essential.
Correct answer is: High efficiency and lightweight
Q.56 In a high‑power AC‑DC converter with a three‑phase diode bridge, the addition of a large inductor on the DC side is mainly to:
Increase output voltage
Reduce ripple current on the DC link
Limit switching speed
Provide isolation
Explanation - The DC‑link inductor smooths the pulsating current, reducing ripple and improving converter performance.
Correct answer is: Reduce ripple current on the DC link
Q.57 Which power electronic device is commonly used in a phase‑controlled dimmer for incandescent lighting?
Thyristor (SCR)
MOSFET
IGBT
Diode
Explanation - SCRs can be triggered at specific phases of the AC waveform to control the average voltage applied to the lamp.
Correct answer is: Thyristor (SCR)
Q.58 The main purpose of an LCL filter in a grid‑connected inverter is to:
Increase output voltage
Reduce output current ripple and filter harmonics
Provide isolation
Regulate input frequency
Explanation - LCL filters attenuate high‑frequency switching harmonics before the inverter output connects to the grid.
Correct answer is: Reduce output current ripple and filter harmonics
Q.59 In a DC‑DC converter, the term "critical conduction mode" (CRM) means:
The inductor current never reaches zero
The inductor current just reaches zero at the end of each switching period
The converter operates at maximum frequency
The output voltage is at its maximum
Explanation - CRM (also called boundary conduction) is the transition between continuous and discontinuous conduction modes.
Correct answer is: The inductor current just reaches zero at the end of each switching period
Q.60 Which of the following is a typical application of a three‑phase PWM inverter in industrial settings?
Battery charging
Variable‑speed drives for AC motors
DC power distribution
Solar panel tracking
Explanation - Three‑phase PWM inverters control motor speed and torque by adjusting voltage magnitude and frequency.
Correct answer is: Variable‑speed drives for AC motors
Q.61 In a resonant converter, the resonant frequency is primarily determined by:
Switching frequency of the controller
Values of the series inductor and capacitor
Input voltage magnitude
Load resistance
Explanation - The resonant LC network sets the natural frequency at which the converter operates efficiently.
Correct answer is: Values of the series inductor and capacitor
Q.62 Which power electronic converter is typically used in an Uninterruptible Power Supply (UPS) to provide backup power from a battery?
Buck converter
Boost converter
DC‑AC inverter
Flyback converter
Explanation - The UPS inverter converts stored DC battery energy into AC to supply the load during a power outage.
Correct answer is: DC‑AC inverter
Q.63 In a high‑power traction inverter, the use of a SiC MOSFET over an IGBT mainly reduces:
Thermal management requirements
Switching frequency
Voltage rating
Gate drive complexity
Explanation - SiC devices have lower conduction and switching losses, resulting in lower heat generation and simplified cooling.
Correct answer is: Thermal management requirements
Q.64 A power electronic system for a high‑speed train typically employs which type of converter to interface with the overhead AC line?
Three‑phase diode bridge
Active front‑end rectifier
Buck‑boost converter
Flyback converter
Explanation - AFEs provide power factor correction and regenerative braking capability for high‑speed rail systems.
Correct answer is: Active front‑end rectifier
Q.65 Which of the following describes a key characteristic of a hysteresis current controller used in power converters?
It uses a fixed switching frequency
It tracks the error between reference and actual current within a band
It requires a transformer for isolation
It operates only in discontinuous conduction mode
Explanation - Hysteresis controllers switch when current deviates beyond predetermined upper or lower limits.
Correct answer is: It tracks the error between reference and actual current within a band
Q.66 In a power electronic converter, the term "soft‑start" refers to:
Gradually ramping up the output voltage or current to limit inrush current
Increasing the switching frequency over time
Using a transformer with a soft magnetic core
Operating the converter at low temperature
Explanation - Soft‑start circuits prevent large inrush currents that could damage components or cause voltage dips.
Correct answer is: Gradually ramping up the output voltage or current to limit inrush current
Q.67 Which power electronic topology is commonly used for high‑frequency isolated power supplies in telecommunications equipment?
Flyback converter
Buck converter
Boost converter
Cuk converter
Explanation - Flyback converters provide isolation and are suitable for the moderate power levels in telecom.
Correct answer is: Flyback converter
Q.68 In a three‑phase induction motor drive, the slip frequency is:
The difference between supply frequency and rotor mechanical speed expressed in Hz
The sum of supply frequency and rotor speed
Always equal to the supply frequency
Zero at rated speed
Explanation - Slip frequency determines the relative motion between rotating magnetic field and rotor, influencing torque.
Correct answer is: The difference between supply frequency and rotor mechanical speed expressed in Hz
Q.69 A power electronic system that supplies a constant voltage regardless of load changes is called:
Current‑mode control
Voltage‑mode control
Constant‑frequency control
Constant‑power control
Explanation - Voltage‑mode control regulates the output voltage to a set point independent of load variations.
Correct answer is: Voltage‑mode control
Q.70 Which of the following is a primary concern when designing power electronics for aerospace applications?
Minimizing electromagnetic interference (EMI)
Maximizing component cost
Using only silicon devices
Operating at low frequencies only
Explanation - EMI can affect sensitive avionics; aerospace designs prioritize low emissions and robust filtering.
Correct answer is: Minimizing electromagnetic interference (EMI)
Q.71 In a high‑power DC link, the typical method to limit the voltage during fault conditions is:
Using a snubber resistor
Adding a crowbar circuit
Increasing the switching frequency
Reducing the input voltage
Explanation - Crowbar circuits short the DC link through a protective device to clamp over‑voltage during faults.
Correct answer is: Adding a crowbar circuit
Q.72 Which power electronic converter topology is inherently bidirectional and can be used for regenerative braking in EVs?
Boost converter
Buck converter
Four‑quadrant inverter
Flyback converter
Explanation - Four‑quadrant inverters can operate in motoring and generating modes, enabling energy recovery during braking.
Correct answer is: Four‑quadrant inverter
Q.73 The term "power density" in power electronics refers to:
The amount of power the device can handle per unit weight or volume
The frequency at which the device switches
The total power loss in the system
The voltage rating of the device
Explanation - High power density is crucial for compact, lightweight designs, especially in automotive and aerospace.
Correct answer is: The amount of power the device can handle per unit weight or volume
Q.74 In a three‑phase inverter, the use of space vector modulation (SVM) compared to sinusoidal PWM results in:
Higher harmonic distortion
Lower DC bus utilization
Higher DC bus voltage utilization and lower harmonic distortion
Simpler implementation
Explanation - SVM efficiently uses the DC bus voltage and reduces total harmonic distortion in the output.
Correct answer is: Higher DC bus voltage utilization and lower harmonic distortion
Q.75 Which of the following power electronic applications typically requires galvanic isolation between input and output?
Battery charger for an electric bike
DC‑DC buck converter for a microcontroller
Isolated medical equipment power supply
LED driver for a flashlight
Explanation - Medical devices must isolate patient‑connected circuits from mains to ensure safety.
Correct answer is: Isolated medical equipment power supply
Q.76 In a power electronic system, the term "efficiency" is defined as:
Output power divided by input power
Input power divided by output power
Output voltage divided by input voltage
Switching frequency divided by load resistance
Explanation - Efficiency indicates how well a converter converts input power into usable output power.
Correct answer is: Output power divided by input power
Q.77 Which power electronic converter is best suited for stepping down a 48 V battery voltage to 12 V for automotive auxiliary loads?
Boost converter
Buck converter
Buck‑boost converter
Cuk converter
Explanation - A buck converter efficiently reduces the higher battery voltage to a lower level required for accessories.
Correct answer is: Buck converter
Q.78 The primary advantage of using a three‑level inverter in medium‑voltage motor drives is:
Reduced component count
Lower output voltage
Reduced voltage stress on devices and lower harmonic content
Higher switching frequency
Explanation - Multilevel inverters split the voltage across multiple devices, reducing stress and improving waveform quality.
Correct answer is: Reduced voltage stress on devices and lower harmonic content
Q.79 In a photovoltaic (PV) system, the function of a DC‑DC boost converter before the inverter is to:
Decrease the voltage to match the inverter input
Increase the voltage to a suitable level for the inverter
Convert DC to AC directly
Provide isolation
Explanation - Boost converters raise the PV array voltage to match the DC‑link voltage required by the inverter.
Correct answer is: Increase the voltage to a suitable level for the inverter
Q.80 Which of the following is a common method to achieve soft‑switching in a power converter?
Increasing the duty cycle
Using a resonant tank circuit
Adding a large inductor
Operating at very low frequencies
Explanation - Resonant circuits allow voltage or current to be zero at the switching instant, achieving soft switching.
Correct answer is: Using a resonant tank circuit
Q.81 In an electric vehicle’s on‑board charger, the main power electronic stages consist of:
AC‑DC rectifier and DC‑DC buck converter
DC‑AC inverter and AC‑DC rectifier
DC‑DC boost converter only
Three‑phase inverter only
Explanation - The charger first rectifies AC mains to DC and then steps down the voltage to safely charge the battery.
Correct answer is: AC‑DC rectifier and DC‑DC buck converter
Q.82 The main purpose of a snubber circuit in a high‑power IGBT switch is to:
Increase switching speed
Reduce voltage overshoot and ringing during turn‑off
Provide isolation
Regulate output voltage
Explanation - Snubbers absorb energy from parasitic inductances, protecting the switch from over‑voltage.
Correct answer is: Reduce voltage overshoot and ringing during turn‑off
Q.83 Which power electronic application uses a high‑frequency transformer to achieve both voltage conversion and isolation?
Linear regulator
Switched‑mode power supply (SMPS)
Resistive heater
Battery charger without isolation
Explanation - SMPS commonly employ high‑frequency transformers for efficient voltage conversion and isolation.
Correct answer is: Switched‑mode power supply (SMPS)
Q.84 In a DC‑link inverter for a motor drive, the DC‑link capacitor primarily serves to:
Provide isolation
Store energy to smooth voltage between switching events
Increase output frequency
Reduce magnetic losses
Explanation - The DC‑link capacitor reduces voltage ripple caused by the inverter’s switching actions.
Correct answer is: Store energy to smooth voltage between switching events
Q.85 Which of the following is an advantage of using SiC MOSFETs in a high‑frequency DC‑DC converter for a solar inverter?
Higher switching losses
Lower switching frequency capability
Reduced size of passive components due to higher switching frequency
Increased gate drive voltage
Explanation - SiC devices enable higher switching frequencies, allowing smaller inductors and capacitors.
Correct answer is: Reduced size of passive components due to higher switching frequency
Q.86 A power electronic converter that can both step up and step down voltage while maintaining a constant output power is known as:
Buck‑boost converter
Cuk converter
SEPIC converter
Z‑source inverter
Explanation - Z‑source inverters provide voltage boost and buck capabilities while delivering constant power.
Correct answer is: Z‑source inverter
Q.87 In a motor drive, the term "regenerative braking" refers to:
Using friction brakes to stop the motor
Feeding mechanical energy back into the electrical grid or battery
Increasing the motor speed rapidly
Disconnecting the motor from the power supply
Explanation - During regenerative braking, the motor acts as a generator, and power electronics route the energy back to the source.
Correct answer is: Feeding mechanical energy back into the electrical grid or battery
Q.88 Which power electronic topology is most suitable for a high‑power (>100 kW) three‑phase motor drive that requires bidirectional power flow?
Six‑step inverter
Two‑level voltage‑source inverter with IGBTs
Three‑phase diode bridge
Flyback converter
Explanation - A two‑level VSI using IGBTs provides high power handling and can operate bidirectionally for regeneration.
Correct answer is: Two‑level voltage‑source inverter with IGBTs
Q.89 In power electronics, the term "over‑modulation" refers to:
Operating the converter beyond its voltage rating
Driving the PWM duty cycle beyond the linear region, causing waveform distortion
Increasing the switching frequency beyond safe limits
Using a larger inductor than required
Explanation - Over‑modulation exceeds the linear modulation range, leading to higher harmonics and possible distortion.
Correct answer is: Driving the PWM duty cycle beyond the linear region, causing waveform distortion
Q.90 Which component in a buck converter controls the output voltage?
Inductor
Diode
Switch (MOSFET/IGBT)
Capacitor
Explanation - The duty cycle of the switching element determines the average voltage transferred to the output.
Correct answer is: Switch (MOSFET/IGBT)
Q.91 A power electronic system for an offshore wind farm typically includes which type of converter to connect to the HVDC link?
Voltage‑source converter (VSC)
Current‑source converter (CSC)
Phase‑controlled rectifier
Buck‑boost converter
Explanation - VSCs provide flexible control of active and reactive power for HVDC interconnections.
Correct answer is: Voltage‑source converter (VSC)
Q.92 In a high‑power LED driver, the term "constant current mode" ensures:
Constant voltage across the LED
Constant current through the LED regardless of voltage variations
Variable brightness based on input voltage
No need for a filter
Explanation - LED brightness depends on current; maintaining constant current protects the LED and stabilizes output.
Correct answer is: Constant current through the LED regardless of voltage variations
Q.93 Which power electronic converter topology is commonly employed in a DC‑DC converter for electric aircraft to achieve high efficiency and low weight?
Flyback converter
Half‑bridge resonant converter
Cuk converter
Buck‑boost converter
Explanation - Half‑bridge resonant converters provide high efficiency with reduced component size, suitable for aerospace.
Correct answer is: Half‑bridge resonant converter
Q.94 In a three‑phase inverter, the term "dead‑time overlap" is undesirable because it can cause:
Increased efficiency
Shoot‑through short circuit
Reduced harmonic distortion
Higher output voltage
Explanation - If dead‑time is insufficient, both high‑side and low‑side switches may conduct simultaneously, creating a short.
Correct answer is: Shoot‑through short circuit
Q.95 Which of the following is a typical use of a bidirectional DC‑DC converter in a hybrid energy storage system?
Charging a battery from a solar panel only
Allowing energy flow both from battery to load and from regenerative sources back to the battery
Stepping up voltage for an inverter
Providing isolation between input and output
Explanation - Bidirectional converters enable both discharge and charge paths, essential for regenerative energy capture.
Correct answer is: Allowing energy flow both from battery to load and from regenerative sources back to the battery
Q.96 In a high‑frequency resonant converter, the switching devices operate at zero voltage or zero current to achieve:
Hard switching
Soft switching
Maximum power loss
Higher EMI
Explanation - Zero‑voltage or zero‑current switching reduces switching losses and electromagnetic interference.
Correct answer is: Soft switching
Q.97 Which power electronic application commonly uses a three‑phase diode bridge followed by a DC‑link capacitor and an inverter?
Uninterruptible Power Supply (UPS)
LED driver
Battery charger
DC motor speed controller
Explanation - A UPS typically rectifies mains AC, stores energy in a DC link, then inverts back to AC during outages.
Correct answer is: Uninterruptible Power Supply (UPS)
Q.98 The main function of a gate driver in a power electronic switch is to:
Provide isolation between input and output
Generate the required voltage and current to turn the switch on and off quickly
Regulate the output voltage
Reduce switching frequency
Explanation - Gate drivers supply proper gate drive signals ensuring fast and reliable switching of MOSFETs/IGBTs.
Correct answer is: Generate the required voltage and current to turn the switch on and off quickly
Q.99 In a power electronics laboratory, a student measures a 120 V rms input to a three‑phase diode bridge. What is the approximate DC voltage on the filter capacitor after the bridge (ignore losses)?
120 V
170 V
240 V
340 V
Explanation - The DC output of a three‑phase bridge ≈ √3 × V_line ≈ 1.732 × 120 V ≈ 208 V. Accounting for diode drop, a typical value is around 170 V in practice for lower‑rated bridges.
Correct answer is: 170 V
Q.100 Which of the following power electronic converters is most appropriate for a high‑efficiency, low‑noise audio amplifier?
Class‑D inverter
Linear regulator
Flyback converter
Buck‑boost converter
Explanation - Class‑D amplifiers use high‑frequency PWM switching to achieve high efficiency with low heat dissipation.
Correct answer is: Class‑D inverter
Q.101 In a power electronic system for an electric locomotive, the use of regenerative braking allows:
Higher traction power only
Energy to be fed back to the overhead line or storage
Increased mechanical wear
Reduced battery capacity
Explanation - Regenerative braking converts kinetic energy back to electrical energy, which can be returned to the grid or stored.
Correct answer is: Energy to be fed back to the overhead line or storage
Q.102 The main reason for using SiC devices in high‑temperature environments such as automotive under‑hood applications is:
Higher cost
Higher breakdown voltage
Higher thermal conductivity and ability to operate at higher junction temperatures
Lower switching speed
Explanation - SiC can operate at temperatures >200 °C, reducing cooling requirements in harsh environments.
Correct answer is: Higher thermal conductivity and ability to operate at higher junction temperatures
Q.103 Which power electronic device is typically used as a free‑wheeling element in a buck converter?
Diode
Capacitor
Resistor
Inductor
Explanation - The diode provides a path for inductor current when the switch is off, preventing voltage spikes.
Correct answer is: Diode
Q.104 In a three‑phase VSC‑HVDC system, the converters are capable of controlling:
Only active power
Only reactive power
Both active and reactive power independently
Neither active nor reactive power
Explanation - Voltage‑source converters can independently regulate active and reactive power flow in HVDC links.
Correct answer is: Both active and reactive power independently
Q.105 Which of the following is a disadvantage of using a simple buck converter for LED lighting applications?
High efficiency
Complex control circuitry
Limited ability to step up voltage when supply voltage is lower than LED forward voltage
Large size
Explanation - A buck converter can only step down voltage; if the supply is lower than required, a boost or buck‑boost is needed.
Correct answer is: Limited ability to step up voltage when supply voltage is lower than LED forward voltage
Q.106 In a power electronic converter, the term "thermal runaway" refers to:
A condition where temperature rises cause increased losses, leading to further temperature rise
A fast increase in switching frequency
A decrease in output voltage
Improved efficiency at high temperature
Explanation - Thermal runaway can damage components if not properly managed with cooling and protection.
Correct answer is: A condition where temperature rises cause increased losses, leading to further temperature rise
Q.107 Which of the following converters is most appropriate for providing isolated 5 V output from a 48 V battery for a microcontroller in an automotive application?
Flyback converter
Boost converter
Buck converter
Cuk converter
Explanation - Flyback converters provide isolation and step‑down capability suitable for low‑power automotive control circuits.
Correct answer is: Flyback converter
Q.108 In a power electronic system, the use of PWM at a high switching frequency primarily helps to:
Increase the output voltage
Reduce the size of filtering components
Increase harmonic distortion
Decrease efficiency
Explanation - Higher switching frequencies move harmonic content to higher frequencies, allowing smaller inductors and capacitors to filter them.
Correct answer is: Reduce the size of filtering components
Q.109 Which power electronic topology is typically used in a high‑power DC motor drive for electric trains to allow both motoring and regeneration?
Six‑step inverter
Two‑level IGBT inverter
Buck‑boost converter
Flyback converter
Explanation - A two‑level inverter using IGBTs can operate in both motoring and generating modes, supporting regeneration.
Correct answer is: Two‑level IGBT inverter
Q.110 In a power electronics context, the term "grid‑forming inverter" is synonymous with:
Grid‑following inverter
Voltage‑source inverter that can set voltage and frequency independently of the grid
Current‑source inverter only
Diode bridge rectifier
Explanation - Grid‑forming inverters act as a voltage source, establishing grid parameters in islanded operation.
Correct answer is: Voltage‑source inverter that can set voltage and frequency independently of the grid
Q.111 Which of the following is a typical application of a three‑phase active front‑end (AFE) rectifier?
Battery charger for a low‑power device
Motor drive with regenerative capability and power factor correction
LED driver
Simple AC‑DC conversion without control
Explanation - AFEs enable bidirectional power flow and improve input power factor, ideal for motor drives.
Correct answer is: Motor drive with regenerative capability and power factor correction
Q.112 The main advantage of using a high‑frequency resonant converter for induction heating is:
Low cost
Reduced electromagnetic interference
Soft switching leading to high efficiency
Large size
Explanation - Resonant converters achieve near‑zero switching loss, which is crucial for the high power density needed in induction heating.
Correct answer is: Soft switching leading to high efficiency
Q.113 In a power electronics system, the term "dead‑time" is essential for:
Ensuring both high‑side and low‑side switches are on simultaneously
Preventing shoot‑through in a half‑bridge inverter
Increasing switching frequency
Providing isolation
Explanation - Dead‑time inserts a brief interval where both switches are off, avoiding a direct short across the supply.
Correct answer is: Preventing shoot‑through in a half‑bridge inverter
Q.114 Which of the following power electronic devices is best suited for high‑frequency (≥500 kHz) switching in a compact DC‑DC converter?
IGBT
Thyristor
MOSFET
Silicon‑controlled rectifier (SCR)
Explanation - MOSFETs can switch efficiently at high frequencies, making them ideal for compact converters.
Correct answer is: MOSFET
Q.115 In a solar PV inverter, the purpose of maximum power point tracking (MPPT) is to:
Maintain a constant output voltage
Adjust the operating point of the PV array to extract the highest possible power
Increase the inverter switching frequency
Provide isolation between PV panels and the grid
Explanation - MPPT algorithms continuously vary the voltage/current to keep the PV array at its peak power point.
Correct answer is: Adjust the operating point of the PV array to extract the highest possible power
Q.116 Which power electronic topology is often used for high‑power, high‑voltage DC transmission (HVDC) because it allows independent control of active and reactive power?
Current‑source converter (CSC)
Voltage‑source converter (VSC)
Phase‑controlled rectifier
Buck converter
Explanation - VSCs can regulate both active and reactive power, making them suitable for flexible HVDC links.
Correct answer is: Voltage‑source converter (VSC)
Q.117 In a three‑phase inverter, the use of space vector PWM (SVPWM) compared to sinusoidal PWM results in:
Higher total harmonic distortion
Lower DC‑bus voltage utilization
Higher DC‑bus voltage utilization and lower harmonic distortion
Simpler implementation
Explanation - SVPWM maximizes the usable DC‑bus voltage and reduces harmonic content in the output.
Correct answer is: Higher DC‑bus voltage utilization and lower harmonic distortion