Question 31 : Natural commutation of an SCR takes place when
1. voltage across the device becomes negative
2. voltage across the device becomes positive
3. gate current becomes zero
4. anode current becomes zero
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Question 32 : The firing-angle delay is
1. inversely proportional to the synchronizing transformer voltage
2. inversely proportional to the control signal voltage
3. directly proportional to the synchronizing transformer voltage
4. directly proportional to the control signal voltage
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Question 33 : In a single pulse semi-converter using two SCRs, the triggering circuit must produce
1. two firing pulses in each half cycle
2. one firing pulse in each half cycle
3. three firing pulses in each cycle
4. one firing pulse in each cycle
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Question 34 : The pulse gating is not suitable of
1. R loads
2. RC loads
3. RL loads
4. It is suitable of every type of load
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Question 35 : The UJT terminals are
1. E, B1 and B2
2. E1, E2 and B
3. E, G and C
4. G, S and D
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Question 36 : Pulse triggering can be only used by the _____________ type of triggering circuit
1. R
2. RC
3. UJT
4. RLC
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Question 37 : If the gating circuits generator negative pulses, then those can be removed by using
1. schmit triggers
2. clippers
3. clampers
4. zener diodes
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Question 38 : In the thyristor gating circuit, the ZCD is used to
1. amplify the voltage
2. produce a train of pulses
3. convert AC input the ramp voltage
4. used to step-down the voltage
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Question 39 : ___________ commutation is usually used in phase-controlled rectifiers
1. line
2. load
3. forced
4. external-pulse
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Question 40 : In case of an RC half wave triggering circuit, the firing angle can be ideally varied between
1. 0 to 180
2. 0 to 90
3. 0 to 120
4. 0 to 360
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