Silicon Controlled Rectifier Overview
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Questions and Answers

What is the main purpose of a Silicon Controlled Rectifier (SCR)?

  • To function as a general diode
  • To convert DC current into AC current
  • To amplify electric signals
  • To control high power applications (correct)

    • How many terminals does a Silicon Controlled Rectifier have?

  • 4 terminals
  • 2 terminals
  • 3 terminals (correct)
  • 5 terminals

    • What type of semiconductor layers make up a Silicon Controlled Rectifier?

  • Three layers of n-type material
  • Four alternating layers of p-type and n-type materials (correct)
  • One layer of a composite semiconductor
  • Two layers of p-type material

    • Which of the following terms is often used interchangeably with Silicon Controlled Rectifier?

    <p>Thyristor</p> Signup and view all the answers

    Who led the team of power engineers that developed the SCR?

    <p>Gordon Hall</p> Signup and view all the answers

    What are the three terminals of a silicon controlled rectifier?

    <p>Anode, Cathode, Gate</p> Signup and view all the answers

    In which region of the V-I characteristics does the SCR not conduct electric current?

    <p>Forward blocking region</p> Signup and view all the answers

    Which junctions are forward biased in the Forward Blocking Mode?

    <p>Junctions J1 and J3</p> Signup and view all the answers

    What happens when the SCR reaches the forward breakdown voltage (VBF)?

    <p>Current flow increases rapidly.</p> Signup and view all the answers

    What happens when a positive voltage is applied to the gate terminal?

    <p>SCR can conduct current with lower anode-cathode voltage</p> Signup and view all the answers

    What defines the reverse blocking region in an SCR?

    <p>Negative voltage on the anode and positive voltage on the cathode.</p> Signup and view all the answers

    In which mode does the SCR exhibit high resistance and prevents current flow despite being forward biased?

    <p>Forward Blocking Mode</p> Signup and view all the answers

    What is the primary role of a TRIAC?

    <p>To control AC loads.</p> Signup and view all the answers

    How does a TRIAC operate when MT2 is at a positive potential relative to MT1?

    <p>Current flows through P1-N1-P2-N2.</p> Signup and view all the answers

    What phenomenon allows the SCR to conduct current during Forward Conducting Mode?

    <p>Minority carriers gaining energy and causing junction breakdown</p> Signup and view all the answers

    What is the role of the external resistance in a TRIAC circuit?

    <p>To limit the excess current</p> Signup and view all the answers

    In which modes does a TRIAC conduct?

    <p>In both positive and negative half cycles</p> Signup and view all the answers

    What is the primary characteristic of a DIAC?

    <p>It conducts in both directions above break over voltage</p> Signup and view all the answers

    Which of the following is a disadvantage of using a TRIAC?

    <p>Less reliable compared to SCR</p> Signup and view all the answers

    What is a primary application of a DIAC?

    <p>Triggering other devices like TRIACs</p> Signup and view all the answers

    Which statement about the V-I characteristics of a DIAC is true?

    <p>The graph forms a shape of letter 'Z'</p> Signup and view all the answers

    How does a DIAC switch from off-state to on-state?

    <p>When applied voltage exceeds break over voltage</p> Signup and view all the answers

    What happens to junction J2 during forward voltage triggering when the forward break over voltage is reached?

    <p>It starts conducting huge current.</p> Signup and view all the answers

    Which triggering method uses a light source to activate the SCR?

    <p>Light Triggering</p> Signup and view all the answers

    What is a critical drawback of using forward voltage triggering in SCR operation?

    <p>It can lead to thermal runaway and damage.</p> Signup and view all the answers

    Which mode of SCR operation occurs when the anode is negative and the cathode is positive?

    <p>Reverse Blocking Mode</p> Signup and view all the answers

    What triggers the SCR in the dt/dv method?

    <p>A sharp increase in voltage over time.</p> Signup and view all the answers

    What phenomenon may occur due to temperature increase in an SCR?

    <p>Increase in number of electron-hole pairs.</p> Signup and view all the answers

    Which SCR triggering method is considered the most reliable?

    <p>Gate Triggering</p> Signup and view all the answers

    What should happen to the gate voltage after the SCR is turned ON?

    <p>It should be removed.</p> Signup and view all the answers

    What is the impact of spurious voltage spikes on SCRs?

    <p>They can induce unwanted triggering.</p> Signup and view all the answers

    What is the primary function of a DIAC in a circuit?

    <p>To trigger TRIACs for symmetrical switching</p> Signup and view all the answers

    Which statement accurately describes the operation of a DIAC?

    <p>It triggers when voltage exceeds a specific threshold in either direction</p> Signup and view all the answers

    How does the two transistor analogy of SCR work?

    <p>It depicts SCR as connected two transistors with feedback through current control</p> Signup and view all the answers

    What happens to the SCR after it is triggered?

    <p>It remains in the conducting state until the anode current drops below a threshold</p> Signup and view all the answers

    What characteristic of DIAC helps in reducing harmonics in a system?

    <p>Symmetrical switching characteristics</p> Signup and view all the answers

    Which of the following is a disadvantage of using a DIAC?

    <p>It only conducts when voltage exceeds 30 volts</p> Signup and view all the answers

    What role does the gate current play in SCR operation?

    <p>It triggers the SCR into conduction</p> Signup and view all the answers

    What does the regeneration process in SCR do after triggering?

    <p>Reinforces the triggering effect and maintains conduction</p> Signup and view all the answers

    Which factor is critical for the reliable turn-on of an SCR?

    <p>Timing and level of the gate triggering signal</p> Signup and view all the answers

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