UL 244A CRD-2012 UL Standard for Safety Solid-State Controls for Appliances - Section Paragraph Reference 24 3 Subject Abnormal Switching Test - Requirements for controls using el.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): ATNZStandard Number: UL 244AEdition Date: April 30, 2003Edition Number: 3Section / Paragraph Reference: 24.3Subject: Abnormal Switching Test - Requirements f

3、or controls using electronictriggering techniques, such as zero-crossing switching, to switch the controlsoutput switching device.DECISION:(NEW SECTION)24.3 Abnormal Switching Test24.3.1 Controls incorporating electronic circuitry to trigger the switching device during a moreadvantageous electrical

4、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 beyond their ratings.24.3.2 Two test samples are prepared and connected as follows:a) The trigger circuit of the

5、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 shall be rated not greater than 3A and not less than the workingvoltage.c) The control shall be covered in a singl

6、e layer of cheesecloth except the mounting surface,and then placed on a softwood surface that has been covered with white tissue paper. Thecheesecloth requirements shall be according to 21.3.d) The rated supply shall be connected through a Branch Circuit Protection device sizedaccording to installat

7、ion requirements.e) The control is connected to its rated electrical load.24.3.3 The prepared test samples shall be operated in accordance with the endurance test requirementsspecifying the number of operating cycles and on/off periods using random switching. The test samplesshall be operated until

8、either the required number of endurance test cycles are achieved or until ultimateresults are demonstrated for 1h stabilized duration.UL COPYRIGHTED MATERIAL NOT AUTHORIZED FOR FURTHER REPRODUCTION ORDISTRIBUTION WITHOUT PERMISSION FROM UL24.3.4 Immediately after each abnormal switching test, each c

9、ontrol shall be subjected to the DielectricVoltage-Withstand Test, Section 33.24.3.5 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 imminent electrical shock, fire orinjury to pe

10、rsons. There shall be:a) No opening of the ground arc detection fuse.b) No burning of the cheese-cloth.c) No opening of the Branch Circuit Protection device.d) No breakdown during the post-dielectric withstand testing.RATIONALE FOR DECISION:This Certification Requirement Decision provides requiremen

11、ts 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 theelectronic control with zero-crossing switching

12、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 dielectric withstand tests. Abnormal switchin

13、g 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 60730-1investigation, since the control has de

14、monstrated 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 arepermitted. This decision reflects cur

15、rent 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. The control has already completed the normal operating conditions testing.Copyright 2012 Underwriters Laboratories In

16、c.UL, in performing its functions in accordance with its objectives, does not guarantee or warrant thecorrectness of Certification Requirement Decisions it may issue or that they will be recognized or adoptedby anyone. Certification Requirement Decisions are the opinion of Underwriters Laboratories

17、Inc. inpractically applying the requirements of the standard. They do not represent formal interpretations of thestandard under American National Standards Institute (ANSI) processes. UL shall not be responsible toanyone for the use of or reliance upon Certification Requirement Decisions by anyone.

18、UL shall not incurany obligation or liability for damages, including consequential damages, arising out of or in connectionwith the use or reliance upon Certification Requirement Decisions. The electronic version of theCertification Requirement Decision is the current version and previously printed

19、copies may be outdated.STANDARD NUMBER: UL 244A -2-UL COPYRIGHTED MATERIAL NOT AUTHORIZED FOR FURTHER REPRODUCTION ORDISTRIBUTION WITHOUT PERMISSION FROM ULThis document is published as a service to ULs certification customersSTANDARD NUMBER: UL 244A -3-UL COPYRIGHTED MATERIAL NOT AUTHORIZED FOR FURTHER REPRODUCTION ORDISTRIBUTION WITHOUT PERMISSION FROM ULSTANDARD NUMBER: UL 244A -4-No Text on This Page