In a 3 phase semiconverter, the firing frequency is equal to line frequency 3 ti

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Question
In a 3 phase semiconverter, the firing frequency is
Options
A. equal to line frequency
B. 3 times the line frequency
C. 6 times the line frequency
D. 12 times the line frequency

Correct Answer

3 times the line frequency

Explanation

Since the circuit has 3 thyristors, firing frequency is three times the line frequency.

Power Electronics problems

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1. In dielectric heating, the thyristor circuits consist of
Options
A. rectifier-chopper combination
B. controlled rectifier
C. ac regulator
D. rectifier-inverter combination

2. In a multiphase chopper, the different choppers operate in
Options
A. series and all simultaneously
B. parallel and one at a time
C. parallel and simultaneously
D. either (b) or (c)

3. In the below figure, the average value of load current is 15 A. The load is highly inductive. The peak value of thyristor current is
Options
A. 15 A
B. 152 A
C.
D. 30 A

4. When thyristors are connected in series and parallel, it may be necessary to have :
Options
A. current derating
B. voltage derating
C. both current and voltage derating
D. none of the above

5. A high frequency series inverter consists of
Options
A. a number of series inverters in series
B. a number of series inverters in parallel
C. a number of parallel inverters in parallel
D. a number of parallel inverters in series

6. A single phase fully controlled bridge rectifier is fed by a source having inductance. The output voltage during overlap period is
Options
A. V_m
B. 0.5 V_m
C. zero
D. 0.5 V_m - voltage drop across inductance

7. A thyristor has its gate current zero. To start conduction the forward voltage must exceed
Options
A. about 0.5 V
B. forward breakover voltage
C. on state voltage
D. peak working off state forward voltage

8. In the below figure the rms voltage across each half of secondary is 200 V. The peak inverse voltage across each of thyristor is
Options
A. 200 V
B. 2(200) V
C. 2(400) V
D. 800 V

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