Power Electronics MCQ Questions & Answers

41

A push pull inverter provides a

A) Highly regulated output B) Constant DC output C) Square wave output D) None of these

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Answer & Solution

Answer: Option C

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42

An inductor is connected in series with SCR to protect it from

A) Excessive high voltage B) Excessive high dv/dt C) Excessive high di/dt D) Excessive large forward current

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Answer & Solution

Answer: Option C

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43

The SCR would be turned OFF by voltage reversal of applied anode-cathode ac supply frequency of

A) 10 kHz B) 10 Hz C) 5 kHz D) 5 Hz

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Answer & Solution

Answer: Option C

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44

An SCR triggered by a current pulse through its gate can be turned off by

A) giving another pulse of the same polarity to the gate B) by giving pulse so the cathode C) by giving pulse to the anode D) by reversing the polarity of anode and cathode voltage

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Answer & Solution

Answer: Option D

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45

A step-down chopper, fed from a 120 volt DC source, operates a DC motor whose armature e.m.f. and armature resistance are 100 volt and 0.5 Ω respectively. With the magnitude control ratio 0.6, the quadrant of operation DC motor is

A) First B) Second C) Third D) Fourth

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Answer & Solution

Answer: Option A

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46

Match List-I with List-II and select the correct answer using the options given below:

List-I (Semiconductor Device)	List-II (Application)
a. Triac	1. Used in HVDC system
b. IGBT	2. Used in pulse generation
c. SCR	3. Used in motor control circuits
d. UJT	4. Used in ac regulators

A) a-1, b-3, c-4, d-2 B) a-4, b-2, c-1, d-3 C) a-1, b-2, c-4, d-3 D) a-4, b-3, c-1, d-2

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Answer & Solution

Answer: Option A

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47

Which device is used in relaxation oscillator?

A) SCR B) Diac C) Triac D) UJT

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Answer & Solution

Answer: Option D

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48

For a single phase half-wave controlled rectifier has 400sin314t as the input voltage and R as the load. For a firing angle of 60° for the SCR, the average output voltage is

A) $$\frac{{400}}{\pi }$$ B) $$\frac{{300}}{\pi }$$ C) $$\frac{{240}}{\pi }$$ D) $$\frac{{200}}{\pi }$$

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Answer & Solution

Answer: Option B

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49

What will be the one cycle surge current of a SCR if it has half cycle surge current rating of 5000 A for 50 Hz supply?

A) 2345.89 A B) 3456.09 A C) 3535.53 A D) 1232.66 A

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Answer & Solution

Answer: Option C

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50

. . . . . . . . is the device which acts like an N-P-N and a P-N-P transistor connected base-tobase and emitter-to-collector.

A) TRIAC B) SCR C) UJT D) DIAC

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Answer & Solution

Answer: Option B

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Power Electronics MCQ Questions & Answers | ECE