Questions

Multiple-choice questions you can practise one by one. Open a question, tap an answer and see at once whether it is right. For a random set, try Quick practice.

32 questions

• A gate trigger pulse arrives while an SCR is reverse-biased. What is the expected result for a conventional SCR?

  Industrial Electronics & Control of Drives › Unit 1: Introduction to Thyristors · Hard

• A designer chooses a heat sink for an SCR. Which set of factors is most relevant?

  Industrial Electronics & Control of Drives › Unit 1: Introduction to Thyristors · Hard

• A TRIAC-based AC controller produces asymmetric half-cycle conduction because of its triggering circuit. What is a likely supply-side concern?

  Industrial Electronics & Control of Drives › Unit 1: Introduction to Thyristors · Hard

• A UJT relaxation oscillator is used to generate firing pulses. If its timing capacitor value is increased with other parameters unchanged, what generally happens?

  Industrial Electronics & Control of Drives › Unit 1: Introduction to Thyristors · Hard

• A power SCR overheats even though its average current is within rating. Which additional check is especially relevant?

  Industrial Electronics & Control of Drives › Unit 1: Introduction to Thyristors · Hard

• An SCR in a high-voltage circuit turns on without a gate pulse when voltage rises very rapidly. Which protection is most directly relevant?

  Industrial Electronics & Control of Drives › Unit 1: Introduction to Thyristors · Hard

• A thyristor is triggered but the anode current never reaches its latching current. What is the likely outcome after the gate pulse is removed?

  Industrial Electronics & Control of Drives › Unit 1: Introduction to Thyristors · Hard

• Why should SCR di/dt be limited during turn-on?

  Industrial Electronics & Control of Drives › Unit 1: Introduction to Thyristors · Medium

• What is the purpose of forced commutation in an SCR circuit?

  Industrial Electronics & Control of Drives › Unit 1: Introduction to Thyristors · Medium

• In a UJT relaxation oscillator, what causes the capacitor to discharge rapidly?

  Industrial Electronics & Control of Drives › Unit 1: Introduction to Thyristors · Medium

• What is the purpose of gate-pulse synchronization with the AC supply?

  Industrial Electronics & Control of Drives › Unit 1: Introduction to Thyristors · Medium

• Why is a snubber network connected across a thyristor in many circuits?

  Industrial Electronics & Control of Drives › Unit 1: Introduction to Thyristors · Medium

• What can cause unwanted SCR turn-on due to a rapid rise in off-state voltage?

  Industrial Electronics & Control of Drives › Unit 1: Introduction to Thyristors · Medium

• What is the difference between latching current and holding current?

  Industrial Electronics & Control of Drives › Unit 1: Introduction to Thyristors · Medium

• Why is an SCR called a latching device?

  Industrial Electronics & Control of Drives › Unit 1: Introduction to Thyristors · Medium

• Which device is commonly used as a relaxation oscillator in thyristor triggering circuits?

  Industrial Electronics & Control of Drives › Unit 1: Introduction to Thyristors · Easy

• What is commutation of an SCR?

  Industrial Electronics & Control of Drives › Unit 1: Introduction to Thyristors · Easy

• Which thyristor parameter is the rate of rise of off-state voltage?

  Industrial Electronics & Control of Drives › Unit 1: Introduction to Thyristors · Easy

• Which thyristor parameter is the rate of rise of anode current?

  Industrial Electronics & Control of Drives › Unit 1: Introduction to Thyristors · Easy

• What is the purpose of a heat sink on a power semiconductor?

  Industrial Electronics & Control of Drives › Unit 1: Introduction to Thyristors · Easy