Extra exam question E7D15
Subelement E7, PRACTICAL CIRCUITS· Group E7D
What is the purpose of a step-start circuit in a high-voltage power supply?
- A.To provide a dual-voltage output for reduced power applications
- B.To compensate for variations of the incoming line voltage
- C.To prevent arcing across the input power switch or relay contacts
- D.To allow the filter capacitors to charge gradually (correct answer)
WhyA step-start circuit in a high-voltage power supply lets the filter capacitors charge gradually. A step-start circuit in a high-voltage power supply limits the large inrush current that would otherwise flow the instant power is applied, by initially charging the filter capacitors gradually through a current-limiting resistor before switching to full, direct connection, answer D. It isn't there to provide a dual-voltage output, isn't compensating for incoming line voltage variation, and while it does reduce switch-contact stress as a side effect, its core purpose is specifically that gradual capacitor charging, not directly preventing arcing.
Published 2026-08-28 · Last updated 2026-08-28 · Question text is verbatim from the 2024-2028 NCVEC Element 4 pool (public domain); the explanation above is original writing, see our methodology.
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