POWER ELECTRONICS QUIZ

Thyristor can be protected from over voltages by using

fuse.

snubber circuit.

heat sink.

voltage clamping device.

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Compared to transistor, ______________ have lower on state conduction losses and higher power handling capability

Semi conductor diodes.

Thyristor.

TRIACs.

MOSFETs.

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A triac can pass a portion of ___________ half-cycle through the load.

Both positive and negative

None of these

Only negative

Only positive

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A string of n parallel SCRs is operated at 72 KA, the rating of each SCR is 1 KA. If derating factor of the string is 0.1. Then calculate the value of n

80.

90.

70.

60.

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What is used to protect the SCR from over current ?

CB and fuse.

Snubber circuit.

Heat sink.

Voltage clamping device.

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If a latching current for the circuit shown in figure is 2 mA. Obtain the value of minimum width of the property turn ON the SCR?

3.2 µs

3 µs.

3.3 µs

3.1 µs

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In forward blocking mode of a thyristor

junction J2 is in reverse bias and J1, J3 is in forward bias.

Junction J1, J3 is in reverse bias and J2 is in forward bias.

Junction J1 and J2 is in forward bias and J3 is in reverse bias.

junction J3 is in forward bias and J1, J2 is in reverse bias.

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The triac is ___________.

A four-terminal device

Like a bidirectional SCR

Not a thyristor

None of these

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An SCR is considered to be a semi controlled device because

it can be turned ON but not OFF with a gate pulse.

it conducts only during one half cycle of an alternating current wave.

it can be turned OFF but not ON with a gate pulse.

it can be turned ON only during one half cycle of an AC.

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When a large surge current of very short duration flows through a thyristor then which one of the following device will operate to protect the thyristor ?

Fast acting current limiting device (FACL fuse).

CB.

Voltage clamping device.

Snubber circuit.

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