27 real Power Electronics questions from the Electrical Core bank, as asked in Indian campus drives and tech interviews. Every question has a verified answer and an AI-tutor explanation on placd — free to start.
1. What is Thyristor (SCR)?
Junior
A.delay between the instant a thyristor becomes forward biased and the gate pulse, which controls the average output voltage of a converter
B.deliberate delay between turning off one switch of an inverter leg and turning on its complement to avoid shoot-through, at the cost of output distortion
C.four-layer PNPN device turned on by a gate pulse and turned off only when anode current falls below the holding current
D.comparison of a sine reference with a high-frequency triangular carrier, where modulation index sets the fundamental output voltage
A.Thyristor (SCR) — comparison of a sine reference with a high-frequency triangular carrier, where modulation index sets the fundamental output voltage
B.Thyristor (SCR) — step-up DC-DC converter with output voltage Vin/(1−D), so the output rises steeply as the duty ratio approaches one
C.Thyristor (SCR) — four-layer PNPN device turned on by a gate pulse and turned off only when anode current falls below the holding current
D.Thyristor (SCR) — step-down DC-DC converter whose average output voltage equals duty ratio times input voltage in continuous conduction
5. Which term means: "delay between the instant a thyristor becomes forward biased and the gate pulse, which controls the average output voltage of a converter"?
A.Firing angle — delay between the instant a thyristor becomes forward biased and the gate pulse, which controls the average output voltage of a converter
B.Firing angle — inverter PWM treating the three legs as one rotating vector, giving about 15% higher DC bus utilisation than sine-triangle PWM
C.Firing angle — four-layer PNPN device turned on by a gate pulse and turned off only when anode current falls below the holding current
D.Firing angle — diode across an inductive load that carries load current when the switch turns off, preventing negative output voltage and improving power factor
A.Buck chopper — comparison of a sine reference with a high-frequency triangular carrier, where modulation index sets the fundamental output voltage
B.Buck chopper — voltage-controlled switch combining MOSFET gate drive with BJT conduction, dominant from a few kW to MW at switching frequencies up to about 20 kHz
C.Buck chopper — step-down DC-DC converter whose average output voltage equals duty ratio times input voltage in continuous conduction
D.Buck chopper — step-up DC-DC converter with output voltage Vin/(1−D), so the output rises steeply as the duty ratio approaches one
A.Boost chopper — step-up DC-DC converter with output voltage Vin/(1−D), so the output rises steeply as the duty ratio approaches one
B.Boost chopper — four-layer PNPN device turned on by a gate pulse and turned off only when anode current falls below the holding current
C.Boost chopper — step-down DC-DC converter whose average output voltage equals duty ratio times input voltage in continuous conduction
D.Boost chopper — deliberate delay between turning off one switch of an inverter leg and turning on its complement to avoid shoot-through, at the cost of output distortion
A.four-layer PNPN device turned on by a gate pulse and turned off only when anode current falls below the holding current
B.deliberate delay between turning off one switch of an inverter leg and turning on its complement to avoid shoot-through, at the cost of output distortion
C.diode across an inductive load that carries load current when the switch turns off, preventing negative output voltage and improving power factor
D.step-down DC-DC converter whose average output voltage equals duty ratio times input voltage in continuous conduction
14. Which term means: "diode across an inductive load that carries load current when the switch turns off, preventing negative output voltage and improving power factor"?
A.Freewheeling diode — voltage-controlled switch combining MOSFET gate drive with BJT conduction, dominant from a few kW to MW at switching frequencies up to about 20 kHz
B.Freewheeling diode — four-layer PNPN device turned on by a gate pulse and turned off only when anode current falls below the holding current
C.Freewheeling diode — comparison of a sine reference with a high-frequency triangular carrier, where modulation index sets the fundamental output voltage
D.Freewheeling diode — diode across an inductive load that carries load current when the switch turns off, preventing negative output voltage and improving power factor
17. Which term means: "comparison of a sine reference with a high-frequency triangular carrier, where modulation index sets the fundamental output voltage"?
A.Sinusoidal PWM — comparison of a sine reference with a high-frequency triangular carrier, where modulation index sets the fundamental output voltage
B.Sinusoidal PWM — four-layer PNPN device turned on by a gate pulse and turned off only when anode current falls below the holding current
C.Sinusoidal PWM — diode across an inductive load that carries load current when the switch turns off, preventing negative output voltage and improving power factor
D.Sinusoidal PWM — deliberate delay between turning off one switch of an inverter leg and turning on its complement to avoid shoot-through, at the cost of output distortion
A.comparison of a sine reference with a high-frequency triangular carrier, where modulation index sets the fundamental output voltage
B.voltage-controlled switch combining MOSFET gate drive with BJT conduction, dominant from a few kW to MW at switching frequencies up to about 20 kHz
C.step-down DC-DC converter whose average output voltage equals duty ratio times input voltage in continuous conduction
D.deliberate delay between turning off one switch of an inverter leg and turning on its complement to avoid shoot-through, at the cost of output distortion
20. Which term means: "voltage-controlled switch combining MOSFET gate drive with BJT conduction, dominant from a few kW to MW at switching frequencies up to about 20 kHz"?
A.IGBT — delay between the instant a thyristor becomes forward biased and the gate pulse, which controls the average output voltage of a converter
B.IGBT — step-up DC-DC converter with output voltage Vin/(1−D), so the output rises steeply as the duty ratio approaches one
C.IGBT — voltage-controlled switch combining MOSFET gate drive with BJT conduction, dominant from a few kW to MW at switching frequencies up to about 20 kHz
D.IGBT — diode across an inductive load that carries load current when the switch turns off, preventing negative output voltage and improving power factor
A.step-up DC-DC converter with output voltage Vin/(1−D), so the output rises steeply as the duty ratio approaches one
B.deliberate delay between turning off one switch of an inverter leg and turning on its complement to avoid shoot-through, at the cost of output distortion
C.delay between the instant a thyristor becomes forward biased and the gate pulse, which controls the average output voltage of a converter
D.voltage-controlled switch combining MOSFET gate drive with BJT conduction, dominant from a few kW to MW at switching frequencies up to about 20 kHz
23. Which term means: "deliberate delay between turning off one switch of an inverter leg and turning on its complement to avoid shoot-through, at the cost of output distortion"?
A.Dead time — deliberate delay between turning off one switch of an inverter leg and turning on its complement to avoid shoot-through, at the cost of output distortion
B.Dead time — inverter PWM treating the three legs as one rotating vector, giving about 15% higher DC bus utilisation than sine-triangle PWM
C.Dead time — four-layer PNPN device turned on by a gate pulse and turned off only when anode current falls below the holding current
D.Dead time — diode across an inductive load that carries load current when the switch turns off, preventing negative output voltage and improving power factor
A.voltage-controlled switch combining MOSFET gate drive with BJT conduction, dominant from a few kW to MW at switching frequencies up to about 20 kHz
B.comparison of a sine reference with a high-frequency triangular carrier, where modulation index sets the fundamental output voltage
C.deliberate delay between turning off one switch of an inverter leg and turning on its complement to avoid shoot-through, at the cost of output distortion
D.inverter PWM treating the three legs as one rotating vector, giving about 15% higher DC bus utilisation than sine-triangle PWM
26. Which term means: "inverter PWM treating the three legs as one rotating vector, giving about 15% higher DC bus utilisation than sine-triangle PWM"?
A.Space vector modulation — inverter PWM treating the three legs as one rotating vector, giving about 15% higher DC bus utilisation than sine-triangle PWM
B.Space vector modulation — step-up DC-DC converter with output voltage Vin/(1−D), so the output rises steeply as the duty ratio approaches one
C.Space vector modulation — diode across an inductive load that carries load current when the switch turns off, preventing negative output voltage and improving power factor
D.Space vector modulation — voltage-controlled switch combining MOSFET gate drive with BJT conduction, dominant from a few kW to MW at switching frequencies up to about 20 kHz
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