Power Electronics - ECE Questions and Answers

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In an ordinary thyristor

turn on and turn off times are equal

turn on time is more than turn off time

turn off time is more than turn on time

turn on time may be equal, less than or more than turn off time

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Thyristors connected in series need :

static equalizing circuit

dynamic equalizing circuit

both static and dynamic equalizing circuits

none of the above

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The symbol in figure is for

SUS

SBS

SCS

None of the above

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If 4 quadrant operation is required we need

dual converter

full converter

semi converter

none of the above

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A single phase half wave converter is feeding a resistive load. Output dc power is P_dc and total power delivered to load is P_ac then

P_dc = P_ac for all values of firing angles

P_dc = P_ac if firing angle is less than 180°

P_dc < P_ac for all values of firing angles

P_dc < P_ac if firing angle is less than 180°

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Which of the following devices exhibit negative resistance characteristics?

UJT

PUT

Both UJT and PUT

UJT, PUT and SBS

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In integral cycle control of ac regulators, the period of integral cycle control, i.e., (m + n) T should be

less than mechanical or thermal time constant of the system

more than the mechanical or thermal time constant of the system

more or less than the mechanical or thermal time constant

very high

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All other parameters remaining the same, a 3 phase bridge inverter with 180° mode of operation

has the same peak thyristor current as in 120° mode of operation

has higher peak thyristor current than in 120° mode of operation

has lower peak thyristor current than in 120° mode of operation

any of the above

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As compared to BJT, MOSFET has

lower switching losses and higher conduction losses

higher switching losses and higher conduction losses

higher switching losses and lower conduction losses

lower switching losses and lower conduction losses