Kiểm tra & Khắc phục sự cốCâu 480 / 521
You need to check whether the insulation of a 480 V motor winding has degraded to ground. Which test instrument is designed for this measurement?
a.A standard digital multimeter set to the 200 ohm range
b.A clamp-on ammeter
c.A megohmmeter (insulation-resistance tester)
d.A plug-in receptacle tester
Giải thích
A megohmmeter applies a high DC test voltage (e.g., 500-1000 V) and reads insulation resistance in the megohm range, revealing breakdown a standard DMM cannot. A DMM's ohm range uses only a few volts and tops out far too low. A clamp ammeter reads current, and a receptacle tester only checks 120 V outlet wiring.
Luyện miễn phí toàn bộ 521 câu hỏi — không cần đăng ký.
Câu hỏi liên quan cùng chủ đề
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