An toànCâu 433 / 521
You are servicing a circuit that feeds a variable frequency drive (VFD) with large DC-bus capacitors. After disconnecting power you must:
a.Immediately touch the terminals to test them
b.Ignore stored energy because it is a low-voltage system
c.Allow/assist the stored energy to dissipate and verify the capacitors are discharged before contact
d.Short the source to ground while it is still energized
Giải thích
Capacitors in VFDs can hold a dangerous charge after power is removed, so you must let them discharge (per manufacturer's time/procedure) and verify they are discharged before touching. Touching immediately or ignoring stored energy risks a shock, and shorting an energized source is dangerous and can cause an arc flash.
Luyện miễn phí toàn bộ 521 câu hỏi — không cần đăng ký.
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