Q.1 Which of the following is the primary advantage of using a Variable Frequency Drive (VFD) on an induction motor?
Increased mechanical wear
Reduced energy consumption at partial load
Higher startup torque
Elimination of motor maintenance
Explanation - A VFD allows the motor speed to be adjusted to match load requirements, which significantly reduces energy usage during partial load operation compared to running the motor at full speed.
Correct answer is: Reduced energy consumption at partial load
Q.2 In a typical 3‑phase induction motor control circuit, what role does the capacitor in a capacitor‑start motor play?
Increase starting torque
Reduce running losses
Provide phase shift for starting torque
Enable regenerative braking
Explanation - The capacitor creates a phase shift in the auxiliary winding, producing a rotating magnetic field that generates the high starting torque required by the motor.
Correct answer is: Provide phase shift for starting torque
Q.3 Which control strategy is most suitable for maintaining a constant speed in a DC motor under varying load conditions?
Open‑loop control
Closed‑loop current control
Closed‑loop speed control
Mechanical governor only
Explanation - Closed‑loop speed control (feedback control) adjusts the armature voltage based on the measured speed, compensating for load changes and maintaining a constant speed.
Correct answer is: Closed‑loop speed control
Q.4 What is the main function of a soft‑starter in an industrial motor application?
Increase torque during startup
Limit the inrush current
Control motor speed
Provide regenerative braking
Explanation - A soft‑starter reduces the initial current surge during motor startup, protecting the supply system and mechanical components from high inrush currents.
Correct answer is: Limit the inrush current
Q.5 In a PLC (Programmable Logic Controller) ladder diagram, which rung symbol represents a normally open (NO) contact?
[ ]
( )
||
&&
Explanation - In ladder logic, the square bracket [ ] denotes a normally open contact that closes when its controlling condition is true.
Correct answer is: [ ]
Q.6 Which of the following best describes a 'servo motor'?
A motor that runs only at fixed speed
An electric motor used in feedback control systems
A motor that uses magnetic levitation
A motor that operates only on DC power
Explanation - Servo motors are designed for precise control of position or speed and are commonly used in robotics and CNC machinery with closed‑loop feedback.
Correct answer is: An electric motor used in feedback control systems
Q.7 Which parameter is most critical when selecting a VFD for a 3‑phase induction motor rated at 10 kW?
Maximum output voltage
Maximum input current
Maximum output frequency
Maximum input power rating
Explanation - The VFD must be able to deliver the motor's rated power without overheating; thus the input power rating must be equal to or exceed the motor’s power requirement.
Correct answer is: Maximum input power rating
Q.8 What is the purpose of a 'zero‑sequence filter' in a three‑phase motor circuit?
To measure the neutral current
To block harmonic currents from the neutral conductor
To balance phase currents
To increase the motor's torque
Explanation - Zero‑sequence filters are installed in the neutral line to suppress low‑frequency harmonic currents generated by unbalanced loads, protecting the power supply.
Correct answer is: To block harmonic currents from the neutral conductor
Q.9 In a three‑phase AC motor drive, which of the following is NOT a common method for torque control?
Direct torque control
Vector control
Scalar control
Thermal control
Explanation - Torque control methods include direct torque control (DTC), vector control, and scalar (V/Hz) control; thermal control manages temperature but does not directly control torque.
Correct answer is: Thermal control
Q.10 Which of the following is an advantage of using a Permanent Magnet Synchronous Motor (PMSM) over an induction motor for robotics applications?
Higher mechanical losses
Lower efficiency at low speed
Higher torque density
Simpler drive electronics
Explanation - PMSMs provide higher torque per unit volume due to permanent magnets, making them ideal for compact robotic joints that require high torque at low speeds.
Correct answer is: Higher torque density
Q.11 What is the main purpose of a 'dead‑time inverter' in power electronics?
Prevent overlapping of high‑side and low‑side switches
Increase switching frequency
Reduce electromagnetic interference
Improve thermal performance
Explanation - Dead‑time insertion ensures there is a brief period where both switches are off, avoiding shoot‑through current that can damage the inverter.
Correct answer is: Prevent overlapping of high‑side and low‑side switches
Q.12 In a typical PLC program for an automated conveyor system, which instruction would be used to delay a process for 5 seconds?
TON
TIMER
DELAY
WAIT
Explanation - The TON (On‑Delay Timer) instruction in ladder logic sets a timer that delays a function for a specified time period, such as 5 seconds.
Correct answer is: TON
Q.13 Which of the following is a key benefit of using a brushless DC motor in an electric vehicle?
Higher maintenance cost
Lower energy density
Higher efficiency and longer life
Need for mechanical commutator
Explanation - Brushless DC motors have no brushes or commutator, reducing wear and increasing efficiency, making them ideal for the high‑performance demands of EVs.
Correct answer is: Higher efficiency and longer life
Q.14 Which type of harmonic distortion is most likely to arise in an induction motor driven by a VFD?
Even order harmonics
Odd order harmonics
Zero order harmonics
All harmonics equally
Explanation - VFDs generate even‑order harmonics (especially 2nd, 4th) due to the switching action of the inverter, which can cause torque ripple and heating.
Correct answer is: Even order harmonics
Q.15 In a CNC machine, what does the 'G‑code' command G01 represent?
Rapid positioning
Linear interpolation with controlled feed rate
Circular interpolation
Set spindle speed
Explanation - G01 is used for controlled linear motion at a specified feed rate, essential for precise machining operations.
Correct answer is: Linear interpolation with controlled feed rate
Q.16 Which of the following is an example of a 'closed‑loop speed controller' used in industrial drives?
Scalar V/Hz drive
Vector control drive
Open‑loop VFD
Soft‑starter only
Explanation - Vector control uses rotor flux orientation and speed feedback to maintain speed, making it a closed‑loop speed control method.
Correct answer is: Vector control drive
Q.17 What is the main function of a 'motor protection relay' in a motor circuit?
Control motor speed
Detect overcurrent and overvoltage conditions
Regulate phase balance
Measure power factor
Explanation - Motor protection relays monitor electrical parameters and disconnect the motor in case of faults to prevent damage.
Correct answer is: Detect overcurrent and overvoltage conditions
Q.18 Which of the following best describes 'Field Weakening' in a DC motor?
Increasing the field flux to boost speed
Reducing the field flux to allow higher speeds
Changing the motor’s mechanical structure
Replacing the field winding with a permanent magnet
Explanation - Field weakening lowers the magnetic flux, enabling the motor to run beyond its base speed by increasing the supply voltage.
Correct answer is: Reducing the field flux to allow higher speeds
Q.19 Which component is essential for synchronizing multiple drives in an industrial production line?
Central PLC
Local microcontroller
Power factor correction capacitor
Grounding rod
Explanation - A central PLC manages the timing and coordination of multiple drives, ensuring synchronized operation of equipment in the production line.
Correct answer is: Central PLC
Q.20 In a 'cascaded vector control' scheme, what is the primary role of the inner current loop?
Control motor speed
Control torque production
Maintain voltage balance
Regulate temperature
Explanation - The inner current loop rapidly controls the stator current to produce the desired torque, while the outer speed loop regulates motor speed.
Correct answer is: Control torque production
Q.21 What type of converter is used in an induction motor VFD to convert AC supply to the desired DC link voltage?
Half‑bridge rectifier
Full‑bridge rectifier
Three‑phase diode bridge
Three‑phase half‑bridge converter
Explanation - A three‑phase diode bridge rectifier converts the three‑phase AC input into a DC voltage for the inverter’s DC link.
Correct answer is: Three‑phase diode bridge
Q.22 Which of the following is NOT a typical fault condition detected by an overcurrent protection relay?
Short circuit
Phase loss
Open circuit
Voltage sag
Explanation - Overcurrent relays detect excessive current due to short circuits or overloads; voltage sag is a voltage‑sensing fault, not overcurrent.
Correct answer is: Voltage sag
Q.23 In a PLC program, what does the 'XIC' instruction stand for?
Examine if Closed
Execute If Command
Extend Input Control
Extract Instant Count
Explanation - XIC is a ladder logic instruction that checks whether an input contact is closed (true) before executing the associated rung.
Correct answer is: Examine if Closed
Q.24 Which of the following is a major advantage of using a 'universal motor' in a household appliance?
High starting torque
Low speed variability
Requires a separate commutator
Limited to AC power only
Explanation - Universal motors are capable of high starting torque and can operate on both AC and DC supplies, making them suitable for appliances like mixers and drills.
Correct answer is: High starting torque
Q.25 In an induction motor, the term 'stator' refers to:
The rotating part of the motor
The stationary part that creates a magnetic field
The rotor’s cooling fan
The power supply transformer
Explanation - The stator is the fixed component of an induction motor, providing the magnetic field that induces current in the rotor.
Correct answer is: The stationary part that creates a magnetic field
Q.26 Which of the following best describes the function of a 'regenerative braking' system in an electric vehicle?
Convert kinetic energy into electrical energy to recharge the battery
Increase motor speed during acceleration
Eliminate the need for a brake pad
Maintain constant voltage in the drive circuit
Explanation - Regenerative braking uses the motor as a generator, feeding energy back into the battery while slowing the vehicle, improving efficiency.
Correct answer is: Convert kinetic energy into electrical energy to recharge the battery
Q.27 Which of the following is a key feature of a 'Soft‑Starter' compared to a VFD?
Higher speed control
Full frequency range
Lower initial current only
Complete torque regulation
Explanation - Soft‑starters only limit the inrush current and provide limited speed control, whereas VFDs can vary speed across a wide range.
Correct answer is: Lower initial current only
Q.28 In a typical three‑phase motor circuit, which type of fault leads to a significant rise in neutral current?
Single‑phase short to ground
Three‑phase short to line
Open phase
Neutral to ground fault
Explanation - A single‑phase short to ground causes an imbalance in phase currents, resulting in a large neutral current to complete the circuit.
Correct answer is: Single‑phase short to ground
Q.29 Which control strategy is most suitable for a high‑precision positioning application such as a 3‑axis CNC router?
Scalar V/Hz control
Direct torque control
Open‑loop drive
Velocity mode with position feedback
Explanation - Position feedback (e.g., with encoders) combined with velocity mode provides the precise control needed for CNC machining.
Correct answer is: Velocity mode with position feedback
Q.30 What is the primary reason for installing a 'harmonic filter' in the power supply of an industrial drive system?
Increase motor speed
Reduce electromagnetic interference (EMI)
Improve power factor
Lower the voltage drop
Explanation - Harmonic filters absorb high‑frequency harmonic currents, reducing EMI and protecting sensitive equipment.
Correct answer is: Reduce electromagnetic interference (EMI)
Q.31 In a typical PLC ladder diagram, what does the 'OTE' instruction perform?
Open the output
Enable the output
Execute the output command
Output test error
Explanation - OTE (Output Energize) sets the designated output to ON when the rung’s condition is true.
Correct answer is: Enable the output
Q.32 Which of the following is a common application of a 'Brushless DC Motor' in industrial settings?
High‑speed conveyors
Heavy‑load winches
Low‑speed pumps
Rotating magnetic field generators
Explanation - Brushless DC motors provide high speed, low maintenance, and precise control, making them ideal for high‑speed conveyor systems.
Correct answer is: High‑speed conveyors
Q.33 In a VFD, which component is responsible for converting the rectified DC voltage to the desired AC output waveform?
Inverter
Rectifier
DC link capacitor
Filter winding
Explanation - The inverter uses power electronic switches to synthesize an AC waveform from the DC link voltage, controlling frequency and voltage.
Correct answer is: Inverter
Q.34 Which of the following best defines a 'Feed‑forward' control strategy in motor drives?
Control based solely on error feedback
Control that anticipates load changes before they occur
A type of mechanical governor
Only used in DC motors
Explanation - Feed‑forward control predicts the effect of load disturbances and adjusts the control input proactively, improving response speed.
Correct answer is: Control that anticipates load changes before they occur
Q.35 What is the main purpose of using a 'Power Factor Correction (PFC)' capacitor bank in an industrial drive?
To reduce voltage drop across cables
To improve the power factor and reduce reactive power
To filter out harmonics
To provide backup power
Explanation - PFC capacitors supply leading reactive power, reducing the lagging reactive power from motors and improving overall power factor.
Correct answer is: To improve the power factor and reduce reactive power
Q.36 In a 'servo control system', which of the following sensors is typically used to provide position feedback?
Accelerometer
Rotary encoder
Thermocouple
Light sensor
Explanation - Rotary encoders provide precise position (and sometimes speed) feedback essential for servo control loops.
Correct answer is: Rotary encoder
Q.37 What is the primary role of a 'current‑sensor' in a DC motor drive?
Measure rotor position
Regulate armature voltage
Provide feedback for torque control
Detect over‑temperature
Explanation - The current sensor monitors armature current, which is proportional to torque, enabling accurate torque regulation.
Correct answer is: Provide feedback for torque control
Q.38 In a three‑phase VFD, what is the purpose of the 'DC link capacitor'?
To store DC energy and smooth voltage fluctuations
To filter out high‑frequency harmonics
To increase the motor speed
To provide mechanical support
Explanation - The DC link capacitor maintains a steady DC voltage across the inverter’s switches, reducing voltage ripple and improving output quality.
Correct answer is: To store DC energy and smooth voltage fluctuations
Q.39 Which type of motor is best suited for use in an industrial robotic arm where high speed and precise position control are required?
Induction motor
Universal motor
Brushless DC motor
Synchronous motor
Explanation - Brushless DC motors combine high speed, compact size, and precise speed control, making them ideal for robotic joints.
Correct answer is: Brushless DC motor
Q.40 In the context of motor drives, what does 'torque ripple' refer to?
Smooth torque variation over time
Irregular torque variations due to electrical or mechanical factors
A constant torque output
Thermal expansion of motor windings
Explanation - Torque ripple is the variation in torque around the motor shaft, caused by switching harmonics, magnetic saturation, or mechanical imbalance.
Correct answer is: Irregular torque variations due to electrical or mechanical factors
Q.41 Which of the following statements about a 'Synchronous Motor' is correct?
It operates at a speed independent of the supply frequency
It has no rotor field winding
Its rotor field can be excited by a DC source
It can only be used in three‑phase systems
Explanation - Synchronous motors use a DC‑excited rotor winding to create a constant magnetic field that locks the rotor speed to the supply frequency.
Correct answer is: Its rotor field can be excited by a DC source
Q.42 Which of the following is a major benefit of using a 'PID controller' in motor speed regulation?
Simplifies hardware design
Eliminates the need for feedback sensors
Provides automatic tuning for all systems
Balances integral, proportional, and derivative actions for optimal response
Explanation - A PID controller adjusts the output using the proportional, integral, and derivative terms, providing precise speed control with minimal steady‑state error.
Correct answer is: Balances integral, proportional, and derivative actions for optimal response
Q.43 Which of the following best describes the function of a 'Neutral Point Tap' in a VFD’s DC link?
To reduce voltage ripple
To provide a reference point for current measurement
To increase the supply voltage
To block DC offset in the inverter output
Explanation - A neutral tap allows accurate measurement of DC link current by providing a stable reference, which is important for current‑sensing control.
Correct answer is: To provide a reference point for current measurement
Q.44 What is the purpose of the 'Soft‑Start' function in a motor drive?
Increase torque during startup
Limit the rate of voltage increase to reduce mechanical stress
Provide constant speed during startup
Regulate power factor
Explanation - Soft‑Start gradually ramps up the voltage, preventing sudden surges that can damage the motor and mechanical components.
Correct answer is: Limit the rate of voltage increase to reduce mechanical stress
Q.45 In a 'cascaded vector control' system, which loop typically has a faster response time?
Speed loop
Torque loop
Flux loop
Position loop
Explanation - The torque (or current) loop responds faster to changes because it directly controls the motor's current, whereas the speed loop operates more slowly.
Correct answer is: Torque loop
Q.46 Which of the following is a typical application of a 'Linear Variable Differential Transformer (LVDT)' in drive systems?
Monitoring temperature
Measuring position in a linear range
Detecting magnetic flux
Providing power to the motor
Explanation - LVDTs provide high‑precision position feedback for linear motion control, used in CNC machines and servo drives.
Correct answer is: Measuring position in a linear range
Q.47 In an industrial automation system, which device is responsible for translating human operator commands into electrical signals that control motors?
PLC
HMI
Motor controller
Sensor
Explanation - The PLC processes inputs from the operator and executes control logic, sending signals to motor drives and other devices.
Correct answer is: PLC
Q.48 Which of the following is NOT a characteristic of a 'Permanent Magnet Synchronous Motor (PMSM)'?
Uses permanent magnets in the rotor
Has variable speed capability
Requires external field excitation
Offers high efficiency at low speeds
Explanation - PMSMs have permanent magnets, so they do not need external field excitation; they rely on the rotor’s built‑in magnetic field.
Correct answer is: Requires external field excitation
Q.49 Which of the following is a common cause of motor overheating in a VFD application?
Excessive voltage ripple
High ambient temperature
Low duty cycle
Correctly sized heat sink
Explanation - High surrounding temperatures reduce heat dissipation, leading to motor overheating, especially when combined with high loads.
Correct answer is: High ambient temperature
Q.50 In a PLC ladder diagram, what does the 'XIO' instruction represent?
Examine if Open
Execute if Open
Exclude I/O
Extend Output
Explanation - XIO tests whether a contact is open (false); if so, the rung logic is executed.
Correct answer is: Examine if Open
Q.51 Which of the following is a key difference between a 'V/Hz drive' and a 'vector drive'?
V/Hz controls torque directly
Vector drives use closed‑loop torque control
V/Hz requires no power supply
Vector drives cannot control speed
Explanation - Vector drives employ vector control to regulate torque via current feedback, while V/Hz drives rely on open‑loop voltage-to-frequency proportionality.
Correct answer is: Vector drives use closed‑loop torque control
Q.52 What is the main function of a 'DC motor controller' in an electric wheelchair?
Increase battery life
Control motor speed and direction
Regulate ambient temperature
Provide internet connectivity
Explanation - The controller modulates the motor’s voltage and current to adjust speed and direction according to the user’s input.
Correct answer is: Control motor speed and direction
Q.53 Which of the following statements about 'Harmonic Resonance' in motor drives is true?
It occurs only in DC drives
It can cause excessive heating in transformers
It is eliminated by increasing supply voltage
It is not a concern in VFDs
Explanation - Harmonic resonance can amplify specific harmonic currents, leading to overheating of transformer cores and other components.
Correct answer is: It can cause excessive heating in transformers
Q.54 Which of the following is a typical application of a 'Power Inverter' in an electric vehicle?
Providing AC power to household outlets
Converting DC from the battery to AC for an induction motor
Charging the battery from a solar panel
Regulating the battery temperature
Explanation - In EVs, an inverter supplies the AC motor with the appropriate voltage and frequency derived from the battery’s DC power.
Correct answer is: Converting DC from the battery to AC for an induction motor
Q.55 What type of sensor is commonly used in an industrial conveyor system to detect the presence of a product?
Infrared proximity sensor
Thermocouple
Accelerometer
Pressure sensor
Explanation - Infrared proximity sensors detect objects without contact, making them ideal for monitoring product presence on conveyors.
Correct answer is: Infrared proximity sensor
Q.56 Which of the following is NOT a typical fault condition detected by a 'Phase‑loss' relay in a motor circuit?
Missing phase
Unbalanced load
Neutral short
Overcurrent
Explanation - Phase‑loss relays detect the absence of a phase; overcurrent faults are detected by separate overcurrent relays.
Correct answer is: Overcurrent
Q.57 In a VFD, the 'duty cycle' of the inverter switches determines:
Motor speed only
Voltage ripple only
Both voltage magnitude and frequency
The type of load
Explanation - The duty cycle controls the average voltage seen by the motor, influencing both magnitude and effective frequency.
Correct answer is: Both voltage magnitude and frequency
Q.58 Which of the following is an example of a 'Synchronous Motor' used in a high‑speed fan?
Three‑phase induction motor
Brushless DC motor
Shaded‑pole motor
Universal motor
Explanation - Brushless DC motors are a type of synchronous motor and are commonly used in high‑speed fans due to their precise speed control.
Correct answer is: Brushless DC motor
Q.59 What is the main benefit of a 'Closed‑loop' controller over an 'Open‑loop' controller in motor drives?
Simpler hardware
Lower startup torque
Reduced speed ripple and better load response
Increased power consumption
Explanation - Closed‑loop controllers continuously adjust based on feedback, improving stability and load compensation compared to open‑loop systems.
Correct answer is: Reduced speed ripple and better load response
Q.60 Which of the following is an advantage of using a 'Brushless DC (BLDC) motor' in an industrial fan application?
High maintenance requirement
Low efficiency at low speeds
High speed and low noise operation
Requirement for a mechanical commutator
Explanation - BLDC motors run smoothly at high speeds and generate low noise, making them suitable for industrial fans.
Correct answer is: High speed and low noise operation
Q.61 In a typical PLC ladder program, which instruction is used to reset a timer?
RES
RST
CLR
CLEAR
Explanation - The RES (Reset) instruction clears a timer or counter in ladder logic, setting its value back to zero.
Correct answer is: RES
Q.62 Which of the following is a primary safety concern when operating a VFD?
Excessive motor speed
High inrush current
Low torque production
Under‑voltage operation
Explanation - High inrush currents can damage power supplies and equipment; protective devices such as fuses and relays are essential.
Correct answer is: High inrush current
Q.63 In a 'Variable Frequency Drive', what effect does increasing the frequency have on the motor's speed?
Decrease speed
Increase speed proportionally
Keep speed constant
Reverse direction
Explanation - Motor speed in a VFD is directly proportional to the supplied frequency, following the speed‑frequency relationship.
Correct answer is: Increase speed proportionally
Q.64 Which of the following best describes 'field weakening' in a DC motor?
Increasing the field current to boost torque
Decreasing the field current to allow higher speeds
Replacing the field winding with a permanent magnet
Adding a second field winding for better control
Explanation - Field weakening reduces magnetic flux, permitting the motor to run faster while maintaining speed control.
Correct answer is: Decreasing the field current to allow higher speeds
Q.65 Which of the following is a typical application of an 'Inverter' in the automotive industry?
Powering the air conditioning unit
Converting AC to DC for the infotainment system
Regenerative braking to feed energy back into the battery
Providing a 12V supply to the engine management system
Explanation - Inverters in EVs convert the motor’s electrical output during braking into DC energy stored in the battery.
Correct answer is: Regenerative braking to feed energy back into the battery
Q.66 Which of the following is the most common cause of high harmonic distortion in an industrial motor drive?
High ambient temperature
Low supply voltage
Switching action of the inverter
Large mechanical load
Explanation - Inverters use high‑frequency switching, which generates harmonic currents that distort the supply waveform.
Correct answer is: Switching action of the inverter
Q.67 Which component in an induction motor is responsible for creating a rotating magnetic field?
Stator winding
Rotor core
Brushes
Commutator
Explanation - The stator’s alternating windings generate a rotating magnetic field that induces current in the rotor.
Correct answer is: Stator winding
Q.68 Which of the following is NOT a function of a 'Power Factor Correction' (PFC) capacitor in a drive system?
Improve power factor
Reduce reactive power
Increase motor torque
Mitigate voltage sags
Explanation - PFC capacitors adjust reactive power, not mechanical torque.
Correct answer is: Increase motor torque
Q.69 What type of control algorithm is used in a typical 'direct torque control' (DTC) system?
Proportional‑integral control
Vector‑based current control
Torque‑current decoupled switching
Speed‑frequency proportional control
Explanation - DTC uses instantaneous torque and flux estimation to directly control stator currents through switching decisions.
Correct answer is: Torque‑current decoupled switching
Q.70 Which of the following is a typical application of a 'PID controller' in a motor drive?
Generating harmonic filtering
Speed regulation in CNC machines
Providing mechanical lubrication
Cooling the motor housing
Explanation - PID controllers are widely used to maintain precise speed in CNC machine drives.
Correct answer is: Speed regulation in CNC machines
Q.71 In a PLC program, the 'FOR' instruction is used for:
Looping a set number of times
Executing a single step
Setting a timer
Resetting a counter
Explanation - The FOR instruction repeats a block of logic a predetermined number of times.
Correct answer is: Looping a set number of times
Q.72 Which of the following best describes a 'three‑phase induction motor' in terms of power consumption?
Consumes less power at lower speeds
Consumes more power as speed decreases
Consumes constant power regardless of speed
Consumes more power at higher speeds
Explanation - Induction motors are constant‑power devices; they draw approximately the same power at all speeds in steady state.
Correct answer is: Consumes constant power regardless of speed
Q.73 Which of the following is a typical fault detected by a 'Ground‑Fault Relay' in a motor drive?
Overcurrent in the motor phase
Phase loss
Short to ground
Neutral to line voltage surge
Explanation - A ground‑fault relay detects current flowing to ground, indicating a short‑to‑ground fault.
Correct answer is: Short to ground
Q.74 Which of the following is a key characteristic of a 'Permanent Magnet Synchronous Motor (PMSM)' used in robotics?
It requires mechanical commutation
It offers high torque density
It cannot operate at low speeds
It uses a DC supply only
Explanation - PMSMs provide high torque per unit volume, essential for robotic applications.
Correct answer is: It offers high torque density
Q.75 In a VFD, what is the purpose of the 'DC link capacitor bank'?
Store energy to smooth voltage fluctuations
Convert AC to DC
Increase the motor's mechanical speed
Provide electromagnetic shielding
Explanation - The DC link capacitor smooths the DC voltage, reducing ripple and ensuring stable inverter output.
Correct answer is: Store energy to smooth voltage fluctuations
Q.76 Which of the following best describes the main function of a 'Neutral‑Point Tap' in a VFD’s DC link?
To provide a reference for current measurement
To reduce voltage ripple
To increase supply voltage
To block DC offset in the inverter output
Explanation - A neutral tap offers a stable reference point for accurate DC‑link current measurement.
Correct answer is: To provide a reference for current measurement
Q.77 What is the primary purpose of a 'Regenerative braking' system in an electric vehicle?
Convert kinetic energy to electrical energy to recharge the battery
Increase the vehicle’s maximum speed
Reduce the battery’s cooling needs
Provide continuous power to the HVAC system
Explanation - Regenerative braking uses the motor as a generator, feeding energy back into the battery during deceleration.
Correct answer is: Convert kinetic energy to electrical energy to recharge the battery