POWER ELECTRONICS QUIZ

In a UJT, the p-type emitter is ___________ doped

Lightly

Heavily

Moderately

None of these

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When the emitter terminal of a UJT is open, the resistance between the base terminal is generally ___________.

Low

Extremely low

High

None of these

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How can we protect SCR from thermal conditions ?

Using heat sink.

Using CB and fuse.

Use of snubber circuit.

Using equalizing circuit.

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If holding current of a thyristor is 2 mA then latching current should be

0.01 A.

0.002 A.

0.009 A.

0.004 A.

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When the temperature increases, the inter-base resistance (RBB) of a UJT ___________.

Remains the same

Decreases

Increases

None of these

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For an SCR gate cathode characteristic is a straight line of 130. For triggered source volume of 15 V and allowable gate power dissipation of 0.5 W compute the gate source resistance?

115 ohm

11.19 ohm

111.9 ohm

108 ohm

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When a UJT is turned ON, the resistance between emitter terminal and lower base terminal ___________

Remains the same

Is increased

Is decreased

None of these

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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 ?

Voltage clamping device.

Fast acting current limiting device (FACL fuse).

Snubber circuit.

CB.

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Which of the following is used in SCR to protect from high dV / dt?

Circuit breaker.

Fuse.

Snubber circuit.

Equalizing circuit.

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During gate recovery time

charge carrier of J1 junction removed.

charge carriers of J2 junction is swept out.

charge carriers of J2 junction recombined.

charge carriers of J3 junction is removed.

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