POWER ELECTRONICS AND DRIVES PART 13
1. The forward break over voltage is the
a) anode-cathode voltage at which conduction starts with gate signal applied
b) anode-cathode voltage at which conduction starts with no gate signal applied
c) gate voltage at which conduction starts with no anode-cathode voltage
d) gate voltage at which conduction starts with anode-cathode voltage applied
a) anode-cathode voltage at which conduction starts with gate signal applied
b) anode-cathode voltage at which conduction starts with no gate signal applied
c) gate voltage at which conduction starts with no anode-cathode voltage
d) gate voltage at which conduction starts with anode-cathode voltage applied
Answer: b
2. For a forward conducting SCR device, as the forward anode to cathode voltage is increased
a) the device turns on at higher values of gate current
b) the device turns on at lower values of gate current
c) the forward impedance of the device goes on increasing
d) the forward impedance of the device goes on decreasing
2. For a forward conducting SCR device, as the forward anode to cathode voltage is increased
a) the device turns on at higher values of gate current
b) the device turns on at lower values of gate current
c) the forward impedance of the device goes on increasing
d) the forward impedance of the device goes on decreasing
Answer: b
3. A thyristor can be bought from the forward conduction mode to forward blocking mode by
a) the dv/dt triggering method
b) applying a negative gate signal
c) applying a positive gate signal
d) applying a reverse voltage across anode-cathode terminals
3. A thyristor can be bought from the forward conduction mode to forward blocking mode by
a) the dv/dt triggering method
b) applying a negative gate signal
c) applying a positive gate signal
d) applying a reverse voltage across anode-cathode terminals
Answer: d
4. Usually the forward voltage triggering method is not used to turn-on the SCR because
a) it increases losses
b) it causes noise production
c) it may damage the junction & destroy the device
d) relatively it’s an inefficient method
4. Usually the forward voltage triggering method is not used to turn-on the SCR because
a) it increases losses
b) it causes noise production
c) it may damage the junction & destroy the device
d) relatively it’s an inefficient method
Answer: c
5. Among the following, the most suitable method to turn on the SCR device is the
a) gate triggering method
b) dv/dt triggering method
c) forward voltage triggering method
d) temperature triggering method
5. Among the following, the most suitable method to turn on the SCR device is the
a) gate triggering method
b) dv/dt triggering method
c) forward voltage triggering method
d) temperature triggering method
Answer: a
6. The forward break over voltage is maximum when
a) Gate current = ∞
b) Gate current = 0
c) Gate current = -∞
d) It is independent of gate current
6. The forward break over voltage is maximum when
a) Gate current = ∞
b) Gate current = 0
c) Gate current = -∞
d) It is independent of gate current
Answer: b
7. For the SCR to remain in the ON (conducting) state
a) gate signal is continuously required
b) no continuous gate signal is required
c) no forward anode-cathode voltage is required
d) negative gate signal is continuously required
7. For the SCR to remain in the ON (conducting) state
a) gate signal is continuously required
b) no continuous gate signal is required
c) no forward anode-cathode voltage is required
d) negative gate signal is continuously required
Answer: b
8. The value of anode current required to maintain the conduction of an SCR even though the gate signal is removed is called as the
a) holding current
b) latching current
c) switching current
d) peak anode current
8. The value of anode current required to maintain the conduction of an SCR even though the gate signal is removed is called as the
a) holding current
b) latching current
c) switching current
d) peak anode current
Answer: b
9. In the reverse blocking mode the middle junction (J2) has the characteristics of that of a
a) transistor
b) capacitor
c) inductor
d) none of the mentioned
9. In the reverse blocking mode the middle junction (J2) has the characteristics of that of a
a) transistor
b) capacitor
c) inductor
d) none of the mentioned
Answer: b
10. ________ are semiconductor thyristor devices which can be turned-on by light of appropriate wavelengths.
a) LGTOs
b) LASERs
c) MASERs
d) LASCRs
10. ________ are semiconductor thyristor devices which can be turned-on by light of appropriate wavelengths.
a) LGTOs
b) LASERs
c) MASERs
d) LASCRs
Answer: d
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