Power Electronics - ECE Questions and Answers

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In a single phase converter using a centre tapped transformer and with a highly inductive load, the firing angles is a. Each thyristor conducts for a period

p - a

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In a parallel inverter

each thyristor is turned on twice during each cycle

each thyristor is turned on once during each cycle

each thyristor is turned on either once or twice in each load cycle

each thyristor may be turned on upto four times in each load cycle

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A step up chopper can give an output voltage

higher than input voltage

lower than input voltage

both higher and lower input voltage

all of the above

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The specified maximum junction temperature of thyristors is about

50°C

80°C

120°C

200°C

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A bridge type single phase cycloconverter changes the frequency f to f/3. Then one half wave of output contains

3 full waves of input

3 half waves of input

6 full waves of input

6 half waves of input

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A half bridge inverter

needs a 3 wire dc supply

may use a two wire or 3 wire dc supply

has higher output voltage if fed from 3 wire dc supply

has higher efficiency if fed from 3 wire dc supply

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A 3 phase series inverter has

12 thyristors

6 thyristors

3 thyristors

3 or 6 thyristors

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In figure, thyristor Th is in off state. When thyristor is turned on, the peak thyristor current can be

5 A

10 A

15 A

20 A

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HVDC systems are preferable for only long distances.

True

False