How can an SCR be protected against excessive temperature?
Correct answer C. Using a heat sink
Subject / 245 questions
Electrical Engineering MCQs
Page 10 of Electrical Engineering multiple-choice questions with answers. Tap an option to check yourself.
Page 10 of 13
Essentially, what is a thyristor?
Correct answer B. Controlled switch
What kind of circuit is a thyristor’s gate (triggering) circuit?
Correct answer C. Low power circuit
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What should happen to the gate signal once a thyristor has turned on properly?
Correct answer C. Gate signal must be removed
Under what anode current condition will an SCR turn off?
Correct answer D. Both A and B
Junction J2 of a thyristor has a capacitance CJ2 = 20 pF, assumed independent of off-state voltage. If a charging current of 16 mA turns the thyristor on, what is the critical dv/dt?
Correct answer B. 800 V/µs
What is a BCT (bidirectional control thyristor) used for?
Correct answer B. High power phase control
Vc1, Vc2 and Vc3 are the forward break-over voltages of a thyristor for gate currents Ig1, Ig2 and Ig3. Which relationship is correct?
Correct answer A. Vc1 > Vc2 > Vc3 when Ig1 < Ig2 < Ig3
Which of the following devices has the highest di/dt and dv/dt capability?
Correct answer C. GTO
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Which method of triggering a thyristor is the most reliable?
Correct answer A. Gate triggering
In which modes does leakage current flow through a thyristor?
Correct answer B. Both forward and reverse blocking modes
What is a disadvantage of fast recovery diodes?
Correct answer C. Doping is carried out
Which device protects a thyristor when a large surge current of very short duration flows through it?
Correct answer A. Fast acting current limiting device (FACL fuse)
A power semiconductor can be damaged by which condition?
Correct answer B. High di/dt
A circuit breaker used for thyristor overcurrent protection operates when the fault current lasts for what length of time?
Correct answer A. A long period
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A GTO is carrying an anode current of 800 A. Roughly how much negative gate current is needed to turn it off?
Correct answer D. 200 A
Which devices protect an SCR against overcurrent?
Correct answer A. Circuit breaker and fuse
Under normal operating conditions, what impedance does a voltage clamping device offer?
Correct answer B. High value
Which semiconductor device behaves like a diode combined with two transistors?
Correct answer A. TRIAC
Under an overvoltage condition, what impedance does a voltage clamping device present?
Correct answer A. Low