低压开关设备和控制设备第5-8部分:控制电路装置和开关元件三位使能开关

[中文适用范围]： This part of IEC 60947 series specifies requirements for three-position enabling switches. These switches are used as components of enabling devices to provide signals that, when activated, allow machine operation to be initiated by a separate start control, and when de-activated, initiate a stop function and prevent initiation of machine operation. These switches are intended to be connected to circuits which rated voltage does not exceed 250 V AC 50 Hz/60 Hz or 300 V DC. This document does not apply to three-position enabling switches for non-electrical control circuits, enabling switches without three-position mechanism, and emergency stop devices. [外文原描述]： IEC 60947-5-8:2020 RLV contains both the official IEC International Standard and its Redline version. The Redline version is available in English only and provides you with a quick and easy way to compare all the changes between the official IEC Standard and its previous edition. IEC 60947-5-8:2020 specifies requirements for three-position enabling switches. These switches are used as components of enabling devices to provide signals that, - when activated, allow machine operation to be initiated by a separate start control, and - when de-activated, -- initiate a stop function, and -- prevent initiation of machine operation. This second edition cancels and replaces the first edition published in 2006. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition: - due to the increasing range of useful applications of three-position enabling switches, note of scope, operational characteristics and tests are reviewed; - figures for example of devices incorporating enabling switch are added in Annex A; - new Annex B for procedure to determine reliability data for the switch used in functional safety applications is added.