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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.
Reason ( R ) : A chopper is dc equivalent to an ac transformer having continuously variable turns ratio.
- a)Both A and R are true and R is the correct explanation of A.
- b)Both A and R are true but R is not the correct explanation of A.
- c)A is true but R is false.
- d)A is false but R is true.
Correct answer is option 'B'. Can you explain this answer?
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Verified Answer
Assertion (A) : In dc choppers, it is essential to provide a separate ...
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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Assertion (A) : In dc choppers, it is essential to provide a separate ...
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.
Explanation:
To understand the given assertion and reason, let's break down the concepts and evaluate them individually.
DC Choppers:
A DC chopper is an electronic device that converts a fixed DC voltage into a variable DC voltage. It consists of a solid-state switch (usually an SCR or a MOSFET) and a diode connected in parallel with the switch. The switch is used to chop the fixed DC voltage into a series of pulses, which can be controlled to achieve the desired output voltage.
Separate Commutation Circuitry:
In DC choppers, the main power SCR (or MOSFET) needs to be turned off at the end of each pulse to allow the current to freewheel through the diode. This process is called commutation. If the SCR is not properly commutated, it may fail to turn off or experience high voltage spikes, leading to device failure.
DC Equivalent to AC Transformer:
The reason states that a chopper is DC equivalent to an AC transformer having a continuously variable turns ratio. This means that the chopper can vary the output voltage by adjusting the duty cycle (on-time vs. off-time) of the switch, similar to how an AC transformer can vary the output voltage by adjusting the turns ratio.
Why a Separate Commutation Circuitry is Essential:
The main power SCR in a DC chopper is typically designed to handle high currents. It is not optimized for fast turn-off times. Therefore, a separate commutation circuitry is essential to ensure proper turn-off of the SCR and prevent it from experiencing high voltage spikes.
The commutation circuitry typically consists of components like capacitors, inductors, and diodes. These components provide a path for the freewheeling current and help in turning off the SCR quickly and safely.
Evaluating the Assertion and Reason:
Assertion (A): In DC choppers, it is essential to provide a separate commutation circuitry to commutate the main power SCR.
This assertion is true because without a separate commutation circuitry, the main power SCR may not be able to turn off properly, leading to device failure.
Reason (R): A chopper is DC equivalent to an AC transformer having continuously variable turns ratio.
This reason is also true because a chopper can vary the output voltage by adjusting the duty cycle, similar to how an AC transformer can vary the output voltage by adjusting the turns ratio.
Conclusion:
Both the assertion and reason are true, but the reason does not provide a correct explanation for the assertion. The reason talks about the DC equivalence of a chopper to an AC transformer, but it does not directly explain why a separate commutation circuitry is essential in DC choppers. Therefore, the correct answer is option B: Both A and R are true, but R is not the correct explanation of A.
Reason (R): A chopper is dc equivalent to an ac transformer having continuously variable turns ratio.
Explanation:
To understand the given assertion and reason, let's break down the concepts and evaluate them individually.
DC Choppers:
A DC chopper is an electronic device that converts a fixed DC voltage into a variable DC voltage. It consists of a solid-state switch (usually an SCR or a MOSFET) and a diode connected in parallel with the switch. The switch is used to chop the fixed DC voltage into a series of pulses, which can be controlled to achieve the desired output voltage.
Separate Commutation Circuitry:
In DC choppers, the main power SCR (or MOSFET) needs to be turned off at the end of each pulse to allow the current to freewheel through the diode. This process is called commutation. If the SCR is not properly commutated, it may fail to turn off or experience high voltage spikes, leading to device failure.
DC Equivalent to AC Transformer:
The reason states that a chopper is DC equivalent to an AC transformer having a continuously variable turns ratio. This means that the chopper can vary the output voltage by adjusting the duty cycle (on-time vs. off-time) of the switch, similar to how an AC transformer can vary the output voltage by adjusting the turns ratio.
Why a Separate Commutation Circuitry is Essential:
The main power SCR in a DC chopper is typically designed to handle high currents. It is not optimized for fast turn-off times. Therefore, a separate commutation circuitry is essential to ensure proper turn-off of the SCR and prevent it from experiencing high voltage spikes.
The commutation circuitry typically consists of components like capacitors, inductors, and diodes. These components provide a path for the freewheeling current and help in turning off the SCR quickly and safely.
Evaluating the Assertion and Reason:
Assertion (A): In DC choppers, it is essential to provide a separate commutation circuitry to commutate the main power SCR.
This assertion is true because without a separate commutation circuitry, the main power SCR may not be able to turn off properly, leading to device failure.
Reason (R): A chopper is DC equivalent to an AC transformer having continuously variable turns ratio.
This reason is also true because a chopper can vary the output voltage by adjusting the duty cycle, similar to how an AC transformer can vary the output voltage by adjusting the turns ratio.
Conclusion:
Both the assertion and reason are true, but the reason does not provide a correct explanation for the assertion. The reason talks about the DC equivalence of a chopper to an AC transformer, but it does not directly explain why a separate commutation circuitry is essential in DC choppers. Therefore, the correct answer is option B: Both A and R are true, but R is not the correct explanation of A.
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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.a)Both A and R are true and R is the correct explanation of A.b)Both A and R are true but R is not the correct explanation of A.c)A is true but R is false.d)A is false but R is true.Correct answer is option 'B'. Can you explain this answer?
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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.a)Both A and R are true and R is the correct explanation of A.b)Both A and R are true but R is not the correct explanation of A.c)A is true but R is false.d)A is false but R is true.Correct answer is option 'B'. Can you explain this answer? for Electrical Engineering (EE) 2024 is part of Electrical Engineering (EE) preparation. The Question and answers have been prepared according to the Electrical Engineering (EE) exam syllabus. Information about 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.a)Both A and R are true and R is the correct explanation of A.b)Both A and R are true but R is not the correct explanation of A.c)A is true but R is false.d)A is false but R is true.Correct answer is option 'B'. Can you explain this answer? covers all topics & solutions for Electrical Engineering (EE) 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for 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.a)Both A and R are true and R is the correct explanation of A.b)Both A and R are true but R is not the correct explanation of A.c)A is true but R is false.d)A is false but R is true.Correct answer is option 'B'. Can you explain this answer?.
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.a)Both A and R are true and R is the correct explanation of A.b)Both A and R are true but R is not the correct explanation of A.c)A is true but R is false.d)A is false but R is true.Correct answer is option 'B'. Can you explain this answer? for Electrical Engineering (EE) 2024 is part of Electrical Engineering (EE) preparation. The Question and answers have been prepared according to the Electrical Engineering (EE) exam syllabus. Information about 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.a)Both A and R are true and R is the correct explanation of A.b)Both A and R are true but R is not the correct explanation of A.c)A is true but R is false.d)A is false but R is true.Correct answer is option 'B'. Can you explain this answer? covers all topics & solutions for Electrical Engineering (EE) 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for 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.a)Both A and R are true and R is the correct explanation of A.b)Both A and R are true but R is not the correct explanation of A.c)A is true but R is false.d)A is false but R is true.Correct answer is option 'B'. Can you explain this answer?.
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