UL 917 CRD-2012 UL Standard for Safety Clock-Operated Switches - Section Paragraph Reference 41 2 Subject Abnormal Switching Test - Requirements for controls using electronic triggi.pdf

1、UL COPYRIGHTED MATERIAL NOT AUTHORIZED FOR FURTHER REPRODUCTION ORDISTRIBUTION WITHOUT PERMISSION FROM ULUNDERWRITERS LABORATORIES INC. CERTIFICATION REQUIREMENT DECISIONThis Certification Requirement Decision is prepared and published by Underwriters Laboratories Inc.(UL). It is normative for the a

2、pplicable UL Product Certification Program(s); however, it is currently notpart of the UL Standard(s) referenced below.Product Category (CCN): WGZRStandard Number: UL 917Edition Date: November 10, 2006Edition Number: 5Section / Paragraph Reference: 41.2Subject: Abnormal Switching Test - Requirements

3、 for controls using electronictriggering techniques, such as zero-crossing switching, to switch the controlsoutput switching device.DECISION:41 Abnormal Operation Test41.1 Adverse conditions of operation41.1.1 When tested in accordance with 41.1.2, there shall not be ignition of the enclosure materi

4、al,exposure of live parts, emission of flame or molten metal, nor glowing or flaming of the material uponwhich the equipment is mounted. The disturbance shall be confined by the enclosure. The disturbanceshall not result in a risk of fire, electric shock, or injury to persons; in parts to become acc

5、essible; or inreduction of spacings to below the required levels.41.1.2 The equipment is to be operated under the most adverse condition of abnormal operation such asstalled-rotor, blocked-armature of relay, burnout of transformer or operation with current-carrying partsshort-circuited, and the like

6、. During the test, the equipment is to rest on white tissue paper on a softwoodsurface and is to be operated continuously until the ultimate results have been determined. In most cases,continuous operation will be necessary until constant temperatures are reached.41.2 Abnormal Switching Test41.2.1 C

7、ontrols incorporating electronic circuitry to trigger the switching device during a moreadvantageous electrical condition, such as at zero crossing, shall be subjected to this abnormal switchingtest. This test is applicable when:a) Loads and circuits are non-safety.b) Switching components are used b

8、eyond their ratings.41.2.2 Two test samples are prepared and connected as follows:a) The trigger circuit of the switching device is to be removed or modified to allow randomswitching.b) A ground arc indicating fuse is connected to accessible dead metal of the control. Theground arc detection fuse sh

9、all be rated not greater than 3A and not less than the workingvoltage.UL COPYRIGHTED MATERIAL NOT AUTHORIZED FOR FURTHER REPRODUCTION ORDISTRIBUTION WITHOUT PERMISSION FROM ULc) The control shall be covered in a single layer of cheesecloth except the mounting surface,and then placed on a softwood su

10、rface that has been covered with white tissue paper. Thecheesecloth shall be, bleached untreated cotton cloth running 14 15 square yards per pound(26 28m2/kg) and for any square inch a count of 32 threads in one direction and 28 in theother direction (for any square centimeter, 13 threads in one dir

11、ection and 11 in the otherdirection).d) The rated supply shall be connected through a Branch Circuit Protection device sizedaccording to installation requirements.e) The control is connected to its rated electrical load.41.2.3 The prepared test samples shall be operated in accordance with the endura

12、nce test requirementsspecifying the number of operating cycles and on/off periods using random switching. The test samplesshall be operated until either the required number of endurance test cycles are achieved or until ultimateresults are demonstrated for 1h stabilized duration.41.2.4 Immediately a

13、fter each abnormal switching test, each control shall be subjected to the DielectricVoltage-Withstand Test, Section 32.41.2.5 The control shall either operate as intended in accordance with the endurance test requirements,or demonstrate an end-of-life fail safe condition with no evidence of an immin

14、ent electrical shock, fire orinjury to persons. There shall be:a) No opening of the ground arc detection fuse.b) No burning of the cheesecloth.c) No opening of the Branch Circuit Protection device.d) No breakdown during the post-dielectric withstand testing.RATIONALE FOR DECISION:This Certification

15、Requirement Decision provides requirements for controls using electronic triggeringtechniques, such as zero-crossing switching, in order to achieve switching of contacts or solid state deviceduring more favorable electrical conditions. To demonstrate capability and required evaluation of theelectron

16、ic control with zero-crossing switching techniques, the control / switching device shall besubjected to an investigation that examines both normal and abnormal contact switching conditions.Normal operating conditions are already evaluated under the existing temperature, overload, endurance,and diele

17、ctric withstand tests. Abnormal switching conditions are evaluated under this abnormal switchingtest. The abnormal switching test is not applicable if the electronic control with zero-crossing switchingcircuitry has been subjected to a UL 991 and UL 1998 (if applicable) investigation, or a UL 60730-

18、1investigation, since the control has demonstrated reliability and production repeatability of thezero-crossing switching circuitry. In general the triggering circuitry is relied on to provide optimumswitching operation. Zero-crossing algorithms are typical examples but there are other methods that

19、arepermitted. This decision reflects current practice.This method can be applied when the following conditions are met: The circuit is NOT a safety circuit. The switching component is used outside of its recognized rating.STANDARD NUMBER: UL 917 -2-UL COPYRIGHTED MATERIAL NOT AUTHORIZED FOR FURTHER

20、REPRODUCTION ORDISTRIBUTION WITHOUT PERMISSION FROM UL The control has already completed the normal operating conditions testing.Copyright 2012 Underwriters Laboratories Inc.UL, in performing its functions in accordance with its objectives, does not guarantee or warrant thecorrectness of Certificati

21、on Requirement Decisions it may issue or that they will be recognized or adoptedby anyone. Certification Requirement Decisions are the opinion of Underwriters Laboratories Inc. inpractically applying the requirements of the standard. They do not represent formal interpretations of thestandard under

22、American National Standards Institute (ANSI) processes. UL shall not be responsible toanyone for the use of or reliance upon Certification Requirement Decisions by anyone. UL shall not incurany obligation or liability for damages, including consequential damages, arising out of or in connectionwith

23、the use or reliance upon Certification Requirement Decisions. The electronic version of theCertification Requirement Decision is the current version and previously printed copies may be outdated.This document is published as a service to ULs certification customersSTANDARD NUMBER: UL 917 -3-UL COPYRIGHTED MATERIAL NOT AUTHORIZED FOR FURTHER REPRODUCTION ORDISTRIBUTION WITHOUT PERMISSION FROM ULSTANDARD NUMBER: UL 917 -4-No Text on This Page