Dịch vụ & Phân phốiCâu 50 / 521
Why must ventilating openings of a dry-type transformer be kept clear of walls and obstructions?
a.To reduce audible noise
b.To meet grounding rules
c.To dissipate heat and prevent overheating
d.To improve power factor
Giải thích
Per 450.9, transformer ventilation must not be blocked so that heat generated by losses can dissipate and the transformer does not overheat. Noise, grounding, and power factor are governed by other rules and are not the purpose of the ventilation clearance.
Trích dẫn luật: 2023 NEC §450.9Luyện miễn phí toàn bộ 521 câu hỏi — không cần đăng ký.
Câu hỏi liên quan cùng chủ đề
- For a transformer over 1000 V or with primary-only protection under 450.3(B), where primary current is 9 A or more, the primary OCPD generally may not exceed what percentage of primary full-load current?
- A transformer has a primary full-load current of 40 A and uses primary-only overcurrent protection. What is the maximum standard primary OCPD (125% rule)?
- Conductors are connected to a transformer secondary without an OCPD at the secondary terminals. What set of rules governs their length and sizing?
- For a single service, what is the maximum number of service disconnecting means permitted (for one set of service-entrance conductors)?
- As a general rule, how must a panelboard be protected against overcurrent?
- What is the minimum depth of working space in front of a 120/240 V panelboard (Condition 1, exposed live parts on one side)?
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