POWER ELECTRONICS AND DRIVES PART 14
1. During the transition time or turn-on time
a) The forward anode voltage decreases from 90 % to 10 % & the anode current also decreases from 90 to 10 % of the initial value
b) The forward anode voltage increases from 10 % to 90 % & the anode current also increases from 10 % to 90 % of the initial value
c) The forward anode voltage decreases from 90 % to 10 % & the anode current increases from 10 % to 90 % of the initial value
d) The forward anode voltage increases from 10 % to 90 % & the anode current decreases from 90% to 10% of the initial value
a) The forward anode voltage decreases from 90 % to 10 % & the anode current also decreases from 90 to 10 % of the initial value
b) The forward anode voltage increases from 10 % to 90 % & the anode current also increases from 10 % to 90 % of the initial value
c) The forward anode voltage decreases from 90 % to 10 % & the anode current increases from 10 % to 90 % of the initial value
d) The forward anode voltage increases from 10 % to 90 % & the anode current decreases from 90% to 10% of the initial value
Answer: c
2. For an SCR the total turn-on time consists of
i) Delay time
ii) Rise time and
iii) Spread time
During the delay time the
a) anode current flows only near the gate
b) anode current rises from zero to very high value
c) losses are maximum
d) anode to cathode voltage is zero
2. For an SCR the total turn-on time consists of
i) Delay time
ii) Rise time and
iii) Spread time
During the delay time the
a) anode current flows only near the gate
b) anode current rises from zero to very high value
c) losses are maximum
d) anode to cathode voltage is zero
Answer: a
3. The minimum value of anode current below which it must fall to completely turn-off the device is called as the
a) holding current value
b) latching current value
c) switching current value
d) peak anode current value
3. The minimum value of anode current below which it must fall to completely turn-off the device is called as the
a) holding current value
b) latching current value
c) switching current value
d) peak anode current value
Answer: a
4. For an SCR the total turn-on time consists of
i) Delay time
ii) Rise time and
iii) Spread time
During the rise time the
a) anode current flows only near the gate
b) anode current rises from zero to very high value
c) losses are maximum
d) anode to cathode voltage is zero
4. For an SCR the total turn-on time consists of
i) Delay time
ii) Rise time and
iii) Spread time
During the rise time the
a) anode current flows only near the gate
b) anode current rises from zero to very high value
c) losses are maximum
d) anode to cathode voltage is zero
Answer: c
5. The latching current is _________ than the holding current
a) lower
b) higher
c) same as
d) negative of
5. The latching current is _________ than the holding current
a) lower
b) higher
c) same as
d) negative of
Answer: b
6. For an SCR the total turn-on time consists of
i) Delay time
ii) Rise time and the
iii) Spread time
The spread time interval depends upon
a) the value of gate current
b) junction temperature
c) area of the cathode
d) area of the anode
6. For an SCR the total turn-on time consists of
i) Delay time
ii) Rise time and the
iii) Spread time
The spread time interval depends upon
a) the value of gate current
b) junction temperature
c) area of the cathode
d) area of the anode
Answer: c
7. For effective turning off of the SCR after the anode current has reached zero value, ______________
a) chargers are injected by applying reverse anode-cathode voltage
b) chargers are removed by applying reverse anode-cathode voltage
c) chargers are injected by applying gate signal
d) chargers are removed by applying gate signal
7. For effective turning off of the SCR after the anode current has reached zero value, ______________
a) chargers are injected by applying reverse anode-cathode voltage
b) chargers are removed by applying reverse anode-cathode voltage
c) chargers are injected by applying gate signal
d) chargers are removed by applying gate signal
Answer: b
8. To avoid commutation failure
a) circuit turn-off time must be greater than the thyristor turn-off time
b) circuit turn-off time must be lesser than the thyristor turn-off time
c) circuit turn-off time must be equal to the thyristor turn-off time
d) none of the above mentioned
8. To avoid commutation failure
a) circuit turn-off time must be greater than the thyristor turn-off time
b) circuit turn-off time must be lesser than the thyristor turn-off time
c) circuit turn-off time must be equal to the thyristor turn-off time
d) none of the above mentioned
Answer: a
9. The gate characteristics of thyristor is a plot of
a) Vg on the X-axis & Ig on the Y-axis
b) Ig on the X-axis & Vg on the Y-axis
c) Va on the X-axis & Ig on the Y-axis
d) Ig on the X-axis & Va on the Y-axis
9. The gate characteristics of thyristor is a plot of
a) Vg on the X-axis & Ig on the Y-axis
b) Ig on the X-axis & Vg on the Y-axis
c) Va on the X-axis & Ig on the Y-axis
d) Ig on the X-axis & Va on the Y-axis
Answer: b
10. The area under the curve of the gate characteristics of thyristor gives the
a) total average gate current
b) total average gate voltage
c) total average gate impedance
d) total average gate power dissipation
10. The area under the curve of the gate characteristics of thyristor gives the
a) total average gate current
b) total average gate voltage
c) total average gate impedance
d) total average gate power dissipation
Answer: d
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