Thyristors are suitable for dc circuit breakers but not for ac circuit breakers.

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Question
Thyristors are suitable for dc circuit breakers but not for ac circuit breakers.
Options
A. True
B. False

Correct Answer

False

Explanation

They are suitable for both dc and ac circuit breakers.

Power Electronics problems

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1. In single phase half wave regulator, the average current over one full cycle
Options
A. is always positive
B. may be positive or negative
C. may be negative
D. is always negative

2. Two thyristor of same rating and same specifications
Options
A. will have equal turn on and turn off periods
B. will have equal turn on but unequal turn off periods
C. may have equal or unequal turn on and turn off periods
D. will have unequal turn on and turn off periods

3. A dc separately excited motor has constant field current. The armature is fed from a single phase supply through a full converter. When a = 0, speed is 500 rpm. If a = 45�, the speed is likely to be
Options
A. about 350 rpm
B. about 250 rpm
C. about 175 rpm
D. about 125 rpm

4. The dynamic equalising circuit consists of a series combination of capacitor C and resistor R_C across each thyristor. This resistance R_C (along with parallel connected diode)
Options
A. limits charging current
B. limits discharging current
C. limits both charging and discharging currents
D. none of the above

5. In a single phase full wave regulator, the firing angles in the positive and negative half cycles are generally
Options
A. equal
B. different
C. equal or different
D. different but sometimes equal

6. If duty cycle is a and the load is a resistance R, the rms value of output voltage is
Options
A. aV
B. a V
C. a²V
D.

8. An 8 bit DAC has a full scale output of 2 mA and full scale error of � 0.5%. If input is 10000000 the range of outputs is
Options
A. 994 to 1014 ?A
B. 990 to 1020 ?A
C. 800 to 1200 ?A
D. none of the above

10. For the K map in the given figure the simplified Boolean expression is
Options
A. A C + A D + ABC
B. A C + A D + ABC
C. A C + A D + ACD
D. A C + A D + AB C

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