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31、ost at www.nfpa.org/docinfo.79-1 NFPA and National Fire Protection Association are registered trademarks of the National Fire Protection Association, Quincy, Massachusetts 02169. Copyright 2017 National Fire Protection Association . All Rights Reserved. NFPA 79 Electrical Standard for Industrial Mac
32、hinery 2018 Edition This edition of NFPA 79, Electrical Standard for Industrial Machinery, was prepared by the Technical Committee on Electrical Equipment of Industrial Machinery and released by the Correlating Committee on National Electrical Code . It was issued by the Standards Council on Novembe
33、r 10, 2017, with an effective date of November 30, 2017, and supersedes all previous editions. This edition of NFPA 79 was approved as an American National Standard on November 30, 2017. Origin and Development of NFPA 79 This standard was rst submitted at the 1961 NFPA Annual Meeting under the title
34、 Electrical Standard for Machine Tools and was tentatively adopted subject to comments. It was extensively revised and resubmitted at the 1962 Annual Meeting, where it was ofcially adopted. In 1965 a revised edition was adopted, reconrmed in 1969, and in 1970, 1971, 1973, 1974, 1977, 1980, 1985, 198
35、7, 1991, 1994, 1997, 2002 and 2007, revised editions were adopted. In September 1941, the metalworking machine tool industry wrote its rst electrical standard to make machine tools safer to operate, more productive, and less costly to maintain, and to improve the quality and performance of their ele
36、ctrical components. That particular standard served as an American “War Standard.” To study the special electrical problems involved with machine tools, in 1941 the Electrical Section of the National Fire Protection Association sanctioned a Special Subcommittee on Wiring, Overcurrent Protection, and
37、 Control of Motor-Operated Machine Tools. This subcommittee, cooperating with machine tool builders, manufacturers of control equipment, and Underwriters Laboratories Inc., conducted tests and investigated the peculiar conditions involved with machine tools that might warrant exception to certain sp
38、ecic National Electrical Code requirements. This investigation resulted, on August 4, 1942, in a Tentative Interim Amendment and rst appeared in a 1943 supplement to the 1940 edition of NFPA 70 , National Electrical Code (NEC), as Article 670, “Machine Tools.” It remained essentially unchanged throu
39、gh the 1959 edition. Meanwhile, manufacturers of other types of industrial equipment erroneously began to follow the specialized practices permitted by Article 670. Late in 1952, a Technical Subcommittee on Fundamentals of Electrically Operated Production Machinery and Material Handling and Processi
40、ng Equipment for Fixed Locations was organized to attempt to group the special requirements of this broad eld into one article. The extremely broad scope introduced so many problems that, in December 1956, this technical subcommittee was reorganized into an NFPA committee whose scope was limited to
41、machine tools and whose objective was the preparation of this NFPA standard with corresponding revisions in Article 670 in the National Electrical Code. Modern machine tool electrical equipment may vary from that of single-motor machines, such as drill presses, that perform simple, repetitive operat
42、ions, to that of very large, multimotored automatic machines that involve highly complex electrical control systems, including electronic and solid-state devices and equipment. Generally these machines are specially designed, factory wired, and tested by the builder and then erected in the plant in
43、which they will be used. Because of their importance to plant production and their usually high cost, they are customarily provided with many safeguards and other devices not often incorporated in the usual motor and control application as contemplated by the National Electrical Code. Although these
44、 machines may be completely automatic, they are constantly attended, when operating, by highly skilled operators. The machine usually incorporates many special devices to protect the operator, protect the machine and building against res of electrical origin, protect the machine and work in process
45、against damage due to electrical failures, and protect against loss ofINDUSTRIAL MACHINERY 79-2 2018 Edition production due to failure of a machine component. To provide these safeguards, it may be preferable to deliberately sacrice a motor or some other component, rather than to chance injury to th
46、e operator, the work, or the machine. It is because of such considerations that this standard varies from the basic concepts of motor protection as contained in the National Electrical Code. As NFPA 79 evolved, it became apparent that certain classes of light industrial machinery (e.g., small drill
47、presses, bench grinders, sanders) were not appropriately covered. The 1977 edition of the standard recognized this problem and purposely excluded tools powered by 2 hp or less. Subsequent to publication of the 1977 standard, a light industrial machinery standard development activity was initiated by
48、 the Power Tool Institute. The 1985 edition of NFPA 79 reects this activity, and appropriate requirements are now included in the standard. In 1975, the Society of the Plastics Industry requested that this standard be enlarged in scope to include plastics machinery. A formal request was received by
49、NFPA in September 1978, and, through the combined efforts of the NFPA 79 committee and representatives of the Society of the Plastics Industry, the scope was broadened to include such machinery in the 1980 edition. In June 1981, the Joint Industrial Council (JIC) Board of Directors acknowledged the dated state of the electrical and electronic standards and requested that NFPA 79 incorporate into its standard the material and topics covered by the JIC electrical (EMP-1-67, EGP-1-67) and electronic (EL-1-71) standards with the intention that the JI
