IEEE - 00036796 Ampacity tables & circuits sizing.pdf

IEEE - 00036796 Ampacity tables & circuits sizing.pdf -...

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AMPACITY TABLES AND CIRCUIT SIZING. OR YOU SIZED THAT FEEDER - HOW?! RICHARD A. FUSELIER, PE MEMBER, IEEE HOECHST CEIANESE CORPORATION POLYESTER FILM DIVISION P.O.BOX 1400 GREER, SC, 29652 ABSTRACT and frustration as the sizing of circuit conductors. 2- UTILIZATloN Electric Code (NEC)[~'have only increased the 5. LENGTH OF CIRCUIT Few subjects generate as much discussion 1. LOAD CURRENT 3. CONTINUOUS OR NON-CONTINUOUS LOAD 4. Recent and proposed changes to the National VOLTAGE DROP - CONTlNUOUS AND INRUSH apparenf Confusion. basic design considerations and applicable 7. CONDUCTOR MATERIAL - COPPER OR ALUMINUM This papet' Sets forth the 6. AMBIENT TEMP. ALONG LENGTH OF CIRCUIT codes and standards requirements necessary for proper circuit sizing. Consideration is given to load current, insulation temperature rating, equip- ment terminal requirements, ambient temperature, voltage drop, energy costs, equipment grounding conductor size, raceway effects, etc. Examples are given describing the "typical," but often incorrect method, and several alternative, but correct methods. Finally, guidelines and ex- amples are given on methods to streamline this process using computer generated, standardized tables for feeders, motors, and transformers. These tables not only reduce design time but assure increased quality control in the design process. INTRODUCTION The sizing of circuit conductors is basic, but there is considerable confusion, misunderstand- ing, ignorance, and misinformation in its imple- mentation. Little real, definitive training has been provided in school or on the job. It is one of those areas where, "you're just supposed to know." Based on personal experience in quiu- ing various engineers and designers, few really know how to properly size circuit conductors, much less streamline the process. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33 * 34. 35. 36. 37. 38. 39. 40. RACEWAY - CONDUIT, WIREWAY, TRAY, ETC. RACEWAY - MAGNETIC OR NON-MAGNETIC SINGLE OR THREE PHASE ENVIRONMENT - DRY, DAMP, WET LOCATION - FREE AIR, BURIED, DUCT BANK, ETC. EQUIPMENT TERM I NATION TEMPERATURE LIMITS INSULATION TEMPERATURE LIMITATIONS DEMAND FACTORS NUMBER OF CURRENT CARRYING CONDUCTORS TOTAL NUMBER OF CONDUCTORS TYPE OF INSULATION AMBIENT TEMPERATURE IN ENCLOSURES AFFECT OF VOLTAGE DROP ON GROUND SIZE PARALLELING OF CONDUCTORS NEXT HIGHER STANDARD DEVICE RATING EQUIPMENT GROUNDING CONDUCTOR SIZE NEUTRAL CONDUCTOR LOADING AND SIZE MEANING OF 'AMBIENT TEMP" OVER TIME ALLOWANCE FOR LOAD GROWTH SHORT CIRCUIT AVAILABLE AND RATING ENERGY COST OF CIRCUIT 12R LOSSES SERVICE, FEEDER, OR BRANCH CIRCUIT MAXIMUM TERMINAL CONDUCTOR SIZE SHORT TIME RATINGS NEC, NESC, NRTL, LOCAL CODES, ETC. AFFECTS OF LOAD ON CURRENT WAVE FORM DIVERSITY SHIELDED OR NON-SHIELDED ROUTING - PULLING TENSIONS, BENDS, ETC.
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  • Fall '19
  • Electrical wiring, Short circuit, Fuse, Circuit breaker, NEC, Current limiting

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