POWER ELECTRONICS AND DRIVES PART 16
1. The voltage safety factor (VSF) for an SCR is the ratio of
a) peak working voltage & peak reverse repetitive voltage
b) dv/dt & di/dt
c) peak repetitive reverse voltage & maximum value of input voltage
d) peak repetitive reverse voltage & rms value of input voltage
b) dv/dt & di/dt
c) peak repetitive reverse voltage & maximum value of input voltage
d) peak repetitive reverse voltage & rms value of input voltage
Answer: c
2. The forward dv/dt rating of an SCR
a) increases with increase in the junction temperature
b) decreases with increase in the junction temperature
c) increases with decrease in the rms value of forward anode-cathode voltage
d) decreases with decrease in the rms value of forward anode-cathode voltage
2. The forward dv/dt rating of an SCR
a) increases with increase in the junction temperature
b) decreases with increase in the junction temperature
c) increases with decrease in the rms value of forward anode-cathode voltage
d) decreases with decrease in the rms value of forward anode-cathode voltage
Answer: a
3. The finger voltage of an SCR is
a) minimum value of Vak to turn on the device with gate triggering
b) maximum value of Vak to turn on the device with gate triggering
c) minimum value of Vak to turn on the device without gate triggering
d) maximum value of Vak to turn on the device without gate triggering
3. The finger voltage of an SCR is
a) minimum value of Vak to turn on the device with gate triggering
b) maximum value of Vak to turn on the device with gate triggering
c) minimum value of Vak to turn on the device without gate triggering
d) maximum value of Vak to turn on the device without gate triggering
Answer: a
4. Which among the following anode current waveforms will have the minimum junction temperature?
a) 100 % DC
b) 25 % DC
c) 50 % DC
d) AC
4. Which among the following anode current waveforms will have the minimum junction temperature?
a) 100 % DC
b) 25 % DC
c) 50 % DC
d) AC
Answer: b
5. An SCR has half cycle surge current rating of 3000 A for 50 Hz. Calculate its one-cycle surge current rating
a) 3121.32 A
b) 2121.32 A
c) 3131.32 A
d) 2131.32 A
5. An SCR has half cycle surge current rating of 3000 A for 50 Hz. Calculate its one-cycle surge current rating
a) 3121.32 A
b) 2121.32 A
c) 3131.32 A
d) 2131.32 A
Answer: b
6. For a SCR the maximum rms on-state current is 35 A. If the SCR is used in a resistive circuit for a rectangular wave with conduction angle of 90°. Calculate the average & rms currents respectively.
a) I/4, I/2
b) I/2, I/√2
c) I/4, I2/2
d) I/4, I/√2
6. For a SCR the maximum rms on-state current is 35 A. If the SCR is used in a resistive circuit for a rectangular wave with conduction angle of 90°. Calculate the average & rms currents respectively.
a) I/4, I/2
b) I/2, I/√2
c) I/4, I2/2
d) I/4, I/√2
Answer: a
7. For an SCR the average & rms values of current are I/4 & I/2 respectively. Calculate the average on-state current rating (ITAV). Take maximum RMS on-state current = 35 A.
a) 8.78 A
b) 10.10 A
c) 17.5 A
d) 24.74 A
7. For an SCR the average & rms values of current are I/4 & I/2 respectively. Calculate the average on-state current rating (ITAV). Take maximum RMS on-state current = 35 A.
a) 8.78 A
b) 10.10 A
c) 17.5 A
d) 24.74 A
Answer: c
8. The amp2-sec rating of the SCR specifies
a) The power dissipated by the device when fault occurs
b) The energy dissipated by the device when fault occurs
c) The energy that the device can absorb before the fault is cleared
d) The energy that the device can absorb while operating in the forward blocking mode.
8. The amp2-sec rating of the SCR specifies
a) The power dissipated by the device when fault occurs
b) The energy dissipated by the device when fault occurs
c) The energy that the device can absorb before the fault is cleared
d) The energy that the device can absorb while operating in the forward blocking mode.
Answer: c
.
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9. The maximum rms current of an SCR is 50 A. For a 120° sine wave conduction the form factor (FF) = 1.878
Find the average on-state current rating (ITAV).
a) 93.9 A
b) 174 A
c) 26.62 A
d) 68.52 A
Find the average on-state current rating (ITAV).
a) 93.9 A
b) 174 A
c) 26.62 A
d) 68.52 A
Answer: c
10. The thermal resistance between junction & the SCR (θjc) has the unit
a) Ω/°C
b) W/Ω
c) °C/W
d) ΩW/°C
10. The thermal resistance between junction & the SCR (θjc) has the unit
a) Ω/°C
b) W/Ω
c) °C/W
d) ΩW/°C
Answer: c
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