Two thyristor of same rating and same specifications will have equal turn on and

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Question
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

Correct Answer

may have equal or unequal turn on and turn off periods

Explanation

Turn on and turn off times of similar SCRs may not be same.

Power Electronics problems

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1. 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

2. 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

3. 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

4. In a 3 phase fully controlled converter the firing frequency is
Options
A. 3 times the line frequency
B. 6 times the line frequency
C. 9 times the line frequency
D. 12 times the line frequency

5. The terminals of a power MOSFET are called
Options
A. emitter, base, collector
B. source, gate, drain
C. source, base, drain
D. emitter, gate, drain

6. 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

8. 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.

10. 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

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