Power Electronics — Part 2 MCQs with Explanations

silicon has small leakage current is the correct answer to “A Silicon Controlled Resistor (SCR) is made up of silicon and not germanium because”. This question is standard in competitive examination syllabi for Power Electronics.

two zener diodes is the correct answer to “An a.c. regulator can be designed with”. This question is standard in competitive examination syllabi for Power Electronics.

Few milliamperes is the correct answer to “The gate current required to turn on an SCR is”. This question is standard in competitive examination syllabi for Power Electronics.

improves the line power factor is the correct answer to “A freewheeling diode in a phase controlled rectifier”. This question is standard in competitive examination syllabi for Power Electronics.

Either 1 or 2 is the correct answer to “Consider the following statements: An SCR, from its OFF state, can be made ON by- 1. increasing its anode voltage 2. increasing its gate current 3. decreasing its gate voltage 4. decreasing its anode current Which one of the following statements is correct”. This question is standard in competitive examination syllabi for Power Electronics.

heat sinks is the correct answer to “Power diode are used with”. This question is standard in competitive examination syllabi for Power Electronics.

a-3, b-1, c-4, d-2 is the correct answer to “Match List-I with List-II and select the correct answer using the options given below: List-I (SCR Rating) List-II (Protective element) a. di/dt limit 1. Snubber circuit b. dv/dt limit 2. Heat sink c. i 2 t limit 3. Series reactor d. Junction temperature limit 4. Fuse”. This question is standard in competitive examination syllabi for Power Electronics.

By applying reverse gate pulse is the correct answer to “How is the GTO turned off”. This question is standard in competitive examination syllabi for Power Electronics.

to improve transient behaviour of the diode is the correct answer to “A power diode has lightly doped n type substrate sandwiched between heavily doped p and n regions”. This question is standard in competitive examination syllabi for Power Electronics.

126 V is the correct answer to “An SCR has an anode supply of sine voltage 200 V r.m.s , 50 Hz applied through a 100 Ω resistor and fired at an angle of 60°. Assuming no voltage drop, the r.m.s. value of the output voltage is nearly”. This question is standard in competitive examination syllabi for Power Electronics.

In the off-state is the correct answer to “In the forward blocking region of a silicon controlled rectifier, the SCR is”. This question is standard in competitive examination syllabi for Power Electronics.

Voltage multiplier is the correct answer to “The electronic circuit that converts AC to DC where the DC output peak value can be greater than the AC input peak value is-”. This question is standard in competitive examination syllabi for Power Electronics.

D is the correct answer to “A step down chopper is operated in the continuous conduction mode in steady state with constant duty ratio D. If V o is the magnitude of the DC output voltage and if V s is the magnitude of the DC input voltage, the ratio $$\frac{{{{\text{V}}_{\text{o}}}}}{{{{\text{V}}_{\text{s}}}}}$$ is given by”. This question is standard in competitive examination syllabi for Power Electronics.

Less than latching current is the correct answer to “In thyristor, holding current is”. This question is standard in competitive examination syllabi for Power Electronics.

SCR is the correct answer to “Which one of the following can be used in the lighting system for power interruptions”. This question is standard in competitive examination syllabi for Power Electronics.

Source inductance is small and load inductance is large is the correct answer to “A voltage source inverter is normally employed when”. This question is standard in competitive examination syllabi for Power Electronics.

TRIAC is the correct answer to “Identify the given symbol.”. This question is standard in competitive examination syllabi for Power Electronics.

800 KΩ > R1 > 2.9 KΩ is the correct answer to “The characteristic of UJT shown in Figure exhibits η = 0.5, V V = 1 V, I V = 10 mA, I P = 20 µA and V P = 14 V. The value of R 1 that will ensure proper turn on and turn off must be”. This question is standard in competitive examination syllabi for Power Electronics.

is negative peak at time t = storage period is the correct answer to “In a GTO, anode current begins to fall when gate current”. This question is standard in competitive examination syllabi for Power Electronics.

Only odd harmonics is the correct answer to “The output voltage waveform of a three phase square wave inverter contains”. This question is standard in competitive examination syllabi for Power Electronics.

$$\frac{{{\text{dv}}}}{{{\text{dt}}}}$$ protection is the correct answer to “Which type of protection is provided for SCR by connecting the snubber circuit across it”. This question is standard in competitive examination syllabi for Power Electronics.

remain same is the correct answer to “After firing an SCR, the gating pulse is removed. Then the current in the SCR will”. This question is standard in competitive examination syllabi for Power Electronics.

Resistors of same values across each SCR is the correct answer to “In order to obtain static voltage equalization in series connected SCRs, connections are made of”. This question is standard in competitive examination syllabi for Power Electronics.

Thyristor requires turn off circuit while transistor does not is the correct answer to “When a thyristor and transistor as a switch are compared, true statement is”. This question is standard in competitive examination syllabi for Power Electronics.

Saw tooth wave is the correct answer to “When UJT is used for triggering an SCR, the wave shape of the signal obtained from UJT circuit is”. This question is standard in competitive examination syllabi for Power Electronics.

0.875 is the correct answer to “A 3-phase full convertor takes a voltage of 200 V. Calculate the supply power factor, if the charging current in the battery is 20 A. Given the power delivered to the load is $$3500\sqrt 2 {\text{ W}}{\text{.}}$$”. This question is standard in competitive examination syllabi for Power Electronics.

6 dB is the correct answer to “What is the peak to average power ratio for the signal x(t) = Asin(ωt) with 50% duty cycle”. This question is standard in competitive examination syllabi for Power Electronics.

1 and 2 only is the correct answer to “Consider the following statements: 1. In a silicon controlled rectifier (SCR), if the cathode gate is reverse-biased, then the SCR cannot fire at all. 2. The turn-on time of an SCR increases with temperature. 3. After an SCR is turned on, it can be made to turn off again by reverse biasing the gate. 4. Gate recovery time is the minimum time that the anode voltage must be maintained below holding voltage V H to turn off the SCR. Which of these statements are correct”. This question is standard in competitive examination syllabi for Power Electronics.

1.7 kW, 871 W, 616 W is the correct answer to “It is required to deliver an output DC power of 500 W to a resistive load. The transformer rating required in case of half-wave, conventional full-wave and bridge rectifiers, respectively, is”. This question is standard in competitive examination syllabi for Power Electronics.

282.84 V is the correct answer to “A single phase full wave mid-point thyristor uses a 220/200 V transformer with central tap on the secondary side. The PIV per thyristor will be:”. This question is standard in competitive examination syllabi for Power Electronics.

Vs * f * Ton is the correct answer to “In dc chopper if T on is the on-time and f is the chopping frequency, then output voltage in terms on input voltage, V s is given by”. This question is standard in competitive examination syllabi for Power Electronics.

UJT is the correct answer to “Which semiconductor device acts like a diode and two resistors”. This question is standard in competitive examination syllabi for Power Electronics.

Only VSI requires feedback diodes is the correct answer to “Which of the following is correct for inverters”. This question is standard in competitive examination syllabi for Power Electronics.

It explains all the region of the device characteristics is the correct answer to “Which one of the following statements regarding the two transistor model of the p-n-p-n four layer device is correct”. This question is standard in competitive examination syllabi for Power Electronics.

0.008 is the correct answer to “The duty cycle of a pulse of width 2 microsecond and repetition frequency 4 kHz is”. This question is standard in competitive examination syllabi for Power Electronics.

Triac is the correct answer to “Which semiconductor device behaves like two SCRs”. This question is standard in competitive examination syllabi for Power Electronics.

3 is the correct answer to “The number of terminals present in IGBT is”. This question is standard in competitive examination syllabi for Power Electronics.

Ringing choke converter is the correct answer to “From circuit design simplicity and economy point of view, one of the following configurations for a converter is the best. Which is that”. This question is standard in competitive examination syllabi for Power Electronics.

SCR is the correct answer to “Which of the following device used for high frequency applications”. This question is standard in competitive examination syllabi for Power Electronics.

1, 2 and 4 are correct is the correct answer to “An SCR can be switched from a non-conducting state to a conducting state by applying 1. A voltage with high $$\frac{{{\text{dv}}}}{{{\text{dt}}}}$$ 2. Voltage greater than forward break over voltage 3. Negative gate current with positive anode voltage 4. Positive gate current with positive anode voltage Which of the following is correct”. This question is standard in competitive examination syllabi for Power Electronics.