Two thyristors of the same rating and datasheet specifications are used. What can be said about their turn-on and turn-off times in practice?
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Amay have equal or unequal turn on and turn off periods
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Bwill have equal turn on and turn off periods
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Cwill have equal turn on but unequal turn off periods
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Dwill have unequal turn on and turn off periods
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Ealways identical due to identical specs
Answer
Correct Answer: may have equal or unequal turn on and turn off periods
Explanation
Introduction / Context:Even when power devices carry the same ratings and come from the same datasheet, real components exhibit manufacturing tolerances. In series/parallel connections or matched legs of converters, recognizing spread in dynamic parameters is important for equalizing networks and safe sharing.
Given Data / Assumptions:
- Two SCRs of same type number and specified ratings.
- Turn-on and turn-off times are measured dynamic parameters with tolerances.
- Operating conditions (temperature, gate drive, current) may differ slightly in-circuit.
Concept / Approach:
Datasheets specify typical/maximum values and ranges; individual units can vary. Therefore, equal dynamic times are not guaranteed, though they can be close. Design must accommodate mismatch via snubbers, equalizing components, and gate drive margins.
Step-by-Step Reasoning:
Compare identical part numbers—expect tolerance band, not exact equality.Recognize temperature and drive differences alter switching times in service.Conclusion: they may be equal or unequal in practice.Verification / Alternative check:
Manufacturers list statistical spreads; production tests show unit-to-unit variance even within the same lot.
Why Other Options Are Wrong:
- Will have equal... too strong; ignores tolerances.
- Will have unequal... also too strong; sometimes they are close enough to be effectively equal.
- Always identical... unrealistic in power semiconductor practice.
Common Pitfalls:
- Assuming identical part numbers imply identical dynamic performance.
- Neglecting equalizing networks for series/parallel SCRs.
Final Answer:
may have equal or unequal turn on and turn off periods