Kiểm tra & Khắc phục sự cốCâu 513 / 521
Before connecting a three-phase motor to a new feeder, why would you use a phase-rotation (phase-sequence) meter on the supply?
a.To determine the phase sequence (A-B-C vs A-C-B) so the motor will rotate in the intended direction
b.To measure insulation resistance of the feeder
c.To read the exact current the motor will draw
d.To verify the neutral is bonded
Giải thích
A phase-rotation meter identifies the sequence of the three phases so you can connect the motor for correct rotation before energizing, avoiding damage from running backward (e.g., pumps, compressors). It does not measure insulation (b), load current (c), or neutral bonding (d).
Luyện miễn phí toàn bộ 521 câu hỏi — không cần đăng ký.
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