Test: Chopper - 1 - Electrical Engineering (EE) MCQ

# Test: Chopper - 1 - Electrical Engineering (EE) MCQ

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## 10 Questions MCQ Test - Test: Chopper - 1

Test: Chopper - 1 for Electrical Engineering (EE) 2024 is part of Electrical Engineering (EE) preparation. The Test: Chopper - 1 questions and answers have been prepared according to the Electrical Engineering (EE) exam syllabus.The Test: Chopper - 1 MCQs are made for Electrical Engineering (EE) 2024 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests for Test: Chopper - 1 below.
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Test: Chopper - 1 - Question 1

### Assertion (A): The principal of step-up chopper can be employed for the regenerative braking of dc motors. Reason (R) : The step-up chopper can be employed in regenerative braking only for increasing motor speeds

Detailed Solution for Test: Chopper - 1 - Question 1

The step-up chopper can be employed in regenerative braking both for increasing and decreasing motor speed provided duty cycle a is so adjusted that Vs/( 1 - a) exceeds the fixed source voiiage V0. Hence, reason is a false statement.

Test: Chopper - 1 - Question 2

### A dc chopper has a T0N of 1 ms and its frequency is 500 Hz. What will be its duty cycle?

Detailed Solution for Test: Chopper - 1 - Question 2

Test: Chopper - 1 - Question 3

### An RLE load is operating in a chopper circuit from a 500 volts dc source as shown in figure For the load, L = 0.06H, R=0 Ω an duty cycle of 0.2, what is the chopping frequency to limit the amolitude of load current excursion to 10 A?

Detailed Solution for Test: Chopper - 1 - Question 3

Test: Chopper - 1 - Question 4

In a type-A chopper, the maximum value of ripple current is

Detailed Solution for Test: Chopper - 1 - Question 4

Test: Chopper - 1 - Question 5

Match List-I (Thyristor chopper circuits) wtih List-ll (Characteristics) and select the correct answer using the codes given below the lists:
List-I
A. Current commutated chopper
B. Voltage commutated chopper
C. Load commutated chopper

List-ll
1. Diode in antiparallel with main SCR
2. Used in high power circuits
3. No requirement of any commutating inductor

Detailed Solution for Test: Chopper - 1 - Question 5

• In a current-commutated chopper a diode is connected in antiparallel with the main thyristor so that voltage drop across the diode reverse biases the main SCR.
• A voltage-commutated chopper is generally used in high-power circuits where load fluctuation is not very large.
• In a load-commutated chopper no commutating inductor is required that is normally costly, bulky and noisy.

Test: Chopper - 1 - Question 6

A chopper circuit shown in figure is initially capacitor stored to supply voltage as shown in figure and SCR T1 is in conduction by drawing constant load current of 20A. The switching frequency is 500Hz. What will be the minimum value of the output voltage?

Detailed Solution for Test: Chopper - 1 - Question 6

The minimum turn-ON time of the SCR is =
For step down chopper, Vo = δ VS

(Vo )min = 50 π V

Test: Chopper - 1 - Question 7

The chopper circuit as shown the thyristor T operated at a duty ratio of 0.8. What will be the value of critical inductance L for which the current falls to zero

Detailed Solution for Test: Chopper - 1 - Question 7

For dc – dc converter the critical inductance value.

V0 = a Vs = 0.8 × 100 = 80 V
I0 = 2A Power P0 = V0 I0 = 160 Watt
f = 500

= 8 × 10–3 H = 8 mH.

Test: Chopper - 1 - Question 8

A boost converter feeds a resistive load from a battery source. Switch is operated at 5000 Hz with duty ratio of 0.4

What will be the average source current in steady state

Detailed Solution for Test: Chopper - 1 - Question 8

In a Boost converter the average current through capacitor is zero.

When switch is closed then

When switch is open

Average current through capacitor = 0

Test: Chopper - 1 - Question 9

A class C chopper is operated from a 220 V battery. The load Is a dc motor with R = 0.1Ω, L= 10 mH and Eb= 100 V. The duty cycle of the chopper to achieve regenerative braking at the rated current of 10 Ampere would be equal to

Detailed Solution for Test: Chopper - 1 - Question 9

Test: Chopper - 1 - Question 10

Assertion (A) : In dc choppers, it is essential to provide a separate commutation circuitry to commutate the main power SCR.
Reason ( R ) : A chopper is dc equivalent to an ac transformer having continuously variable turns ratio.

Detailed Solution for Test: Chopper - 1 - Question 10

Since the input supply to a dc chopper is fixed do voltage therefore, natural commutation is not possible in a dc chopper. Due to this reason a separate commutation circuit is required to commutate the main power SCR in a dc chopper. Reason is also a true statement but not the correct explanation of assertion.

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