《UL-SUBJECT-508B-1994.pdf》由会员分享，可在线阅读，更多相关《UL-SUBJECT-508B-1994.pdf（8页珍藏版）》请在三一文库上搜索。
1、STDOUL SUBJECT 508B-ENGL L77q 7275775 Ob715Li5 380 August 31, 1994 I SUBJECT 508B OUTLINE OF INVESTIGATION FOR RELAYS USED IN INFORMATION TECHNOLOGY EQUIPMENT Issue Number 1 AUGUST 31, 1994 COPYRIGHT 1994 UNDERWRITERS LABORATORIES INC. COPYRIGHT Underwriters Laboratories Inc. Licensed by Information
2、 Handling Services COPYRIGHT Underwriters Laboratories Inc. Licensed by Information Handling Services STD-UL SUBJECT 508B-ENGL L77i 7275775 Ob7154b 217 2 RELAYS USED IN INFORMATION TECHNOLOGY EQUIPMENT - SUBJECT 508B AUGUST 31,1994 No Text on This Page COPYRIGHT Underwriters Laboratories Inc. Licens
3、ed by Information Handling Services COPYRIGHT Underwriters Laboratories Inc. Licensed by Information Handling Services STD-UL SUBJECT 5OBB-ENGL 1794 9275795 Ob71547 153 W AUGUST 31,1994 RELAYS USED IN INFORMATION TECHNOLOGY EQUIPMENT - SUBJECT 508B 3 CONTENTS FOREWORD INTRODUCTION I Scope . . . . .
4、. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2 Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3 General . . . . . . . . . . . . . . . . . . . . . . . . . .
5、 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 CONSTRUCTION 4 Spacings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5 Securement ofwiring and Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6、 . . . . . . . . . 7 6 Flammability of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 PERFORMANCE 7 Electric Strength Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 8 Primary Power Isolat
7、ion (optional) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 9 Safety Interlocks (optional) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 COPYRIGHT Underwriters Laboratories Inc. Licensed by Information Handling Services C
8、OPYRIGHT Underwriters Laboratories Inc. Licensed by Information Handling Services 4 RELAYS USED IN INFORMATION TECHNOLOGY EQUIPMENT - SUBJECT 5088 AUGUST 31,1994 FOREWORD A. This Outline of Investigation contains basic requirements for products covered by Underwriters Laboratories Inc. (UL) under it
9、s Follow-Up Service for this category within the limitations given below and in the Scope section of this Outline of Investigation. They are subject to revision as further experience and investigation may show is necessary or desirable. B. The observance of these requirements by a manufacturer is on
10、e of the conditions of the continued coverage of the manufacturers product. C. A product which complies with the text of this Outline of Investigation will not necessarily be judged to comply with the Outline of Investigation if, when examined and tested, it is found to have other features which imp
11、air the level of safety contemplated by these requirements. D. A product employing materials or having forms of construction differing from those detailed in the requirements of this Outline of Investigation may be examined and tested according to the intent of the requirements and, if found to be s
12、ubstantially equivalent, may be judged to comply with the Outline of Investigation. E. UL, in performing its functions in accordance with its objectives, does not assume or undertake to discharge any responsibility of the manufacturer or any other party. The opinions and findings of UL represent its
13、 professional judgment given with due consideration to the necessary limitations of practical operation and state of the art at the time the Outline of Investigation is processed. UL shall not be responsible to anyone for the use of or reliance upon this Outline of Investigation by anyone. UL shall
14、not incur any obligation or liability for damages, including consequential damages, arising out of or in connection with the use, interpretation of, or reliance upon this Outline of Investigation. F. Many tests required by the Outline of Investigations of UL are inherently hazardous and adequate saf
15、eguards for personnel and property shall be employed in conducting such tests. COPYRIGHT Underwriters Laboratories Inc. Licensed by Information Handling Services COPYRIGHT Underwriters Laboratories Inc. Licensed by Information Handling Services STD-UL SUBJECT 508B-ENGL 177Li 9275775 Ob715Li7 T2b D A
16、UGUST 31,1994 RELAYS USED IN INFORMATION TECHNOLOGY EQUIPMENT - SUBJECT 508B 5 INTRODUCTION 1 Scope 1.1 This Outline of Investigation covers the requirements applicable to relays intended for use in accordance with the Standard for Safety of Information Technology Equipment including Electrical Busi
17、ness Equipment, UL 1950. 1.2 The relays covered are limited to those with air gap isolation or a barrier of solid insulation between coil and contacts (electromechanical types) or between input and output circuits (solid state types). This separation between coil and contacts or input and output cir
18、cuits shall comply with the requirements for basic, double, or reinforced insulation as specified in UL 1950. 1.3 Limiting impedance, as described in the Standard for Industrial Control Equipment, UL 508, is not considered a suitable means of isolation between input and output circuits. 1.4 An optic
19、al isolator may be used in solid state relays to comply with the air gap or solid insulation requirement. 2 Glossary 2.1 For the purpose of this Outline of Investigation, the following definitions apply. See UL 1950 for additional definitions. 2.2 BASIC INSULATION - Insulation that provides basic pr
20、otection against the risk of electric shock. 2.3 DOUBLE INSULATION - Insulation comprising both basic insulation and supplementary insulation. 2.4 EXTRA-LOW VOLTAGE (ELV) - A voltage between conductors or between a conductor and earth ground not exceeding 42.4 V peak, or 60 V dc, existing in a secon
21、dary circuit that is separated from hazardous voltage by at least basic insulation, but does not meet the requirements for a SELV circuit or a limited current circuit as defined in UL 1950. 2.5 HAZARDOUS VOLTAGE - A voltage exceeding 42.4 V peak, or 60 V dc, existing in a circuit that does not meet
22、the requirements for a limited current circuit as defined in UL 1950. 2.6 OPERATIONAL INSULATION - Insulation needed for the correct operation of the equipment. Operational insulation does not protect against risk of electric shock. It may, however, provide a degree of protection against the risk of
23、 ignition and exposure to fire. 2.7 PRIMARY CIRCUIT - An internal circuit that is directly connected to the external supply mains or other equivalent source (such as a motor-generator set) that supplies the electric power. It includes the primary windings of transformers, motors, other loading devic
24、es, and the means of connection to supply mains. 2.8 REINFORCED INSULATION - A single insulation that provides protection against risk of electric shock equivalent to double insulation under the conditions specified in UL 1950. Reinforced insulation does not need to be in one homogeneous piece. It m
25、ay comprise several layers that cannot be tested as supplementary or basic insulation. COPYRIGHT Underwriters Laboratories Inc. Licensed by Information Handling Services COPYRIGHT Underwriters Laboratories Inc. Licensed by Information Handling Services 1 STD-UL SUBJECT SIAB-ENGL I994 H 7275775 0b915
26、50 7r18 6 RELAYS USED IN INFORMATION TECHNOLOGY EQUIPMENT - SUBJECT 5088 AUGUST 31,1994 2.9 SAFETY EXTRA-LOW VOLTAGE (SELV) CIRCUIT - A secondary circuit that is so designed and protected that under normal and single fault conditions the voltage between any two accessible parts, or between one acces
27、sible part and the equipment protective earthing terminal for Class I equipment, does not exceed a safe value. Under normal conditions this limit is either 42.4 V peak, or 60 V dc. Under fault conditions, higher limits are specified in UL 1950 for transient deviation. 2.10 SAFETY INTERLOCK - A means
28、 either of reducing the likelihood of accessing a hazardous area until the hazard is removed or of automatically removing the hazardous condition if access is gained. 2.1 1 SECONDARY CIRCUIT - A circuit that has no direct connection to primary power and derives its power from a transformer, converte
29、r, or equivalent isolation device situated within the equipment. Some solid state devices may provide equivalent isolation. 2.12 SUPPLEMENTARY INSULATION - Independent insulation applied in addition to basic insulation in order to reduce the risk of electric shock in the event of a failure of the ba
30、sic insulation. 3 General 3.1 In addition to complying with the applicable requirements in UL 1950, the relays shall also comply with the applicable requirements in the Standard for Industrial Control Equipment, UL 508. References to UL 1950 are to the Second Edition of that standard, and references
31、 to UL 508 are to the Sixteenth Edition of that Standard. 3.2 The following are two examples of typical relay constructions covered by this Outline of Investigation. These examples specify the circuit construction and the corresponding insulation that would be required for their end-product applicat
32、ion. a) A relay containing hazardous voltage and SELV circuits. This relay construction requires double or reinforced insulation between hazardous voltage and SELV circuits; basic insulation between hazardous voltage circuits and dead metal parts; and operational insulation within each individual ci
33、rcuit; b) A relay containing hazardous voltage and ELV circuits. This relay construction requires basic insulation between hazardous voltage and ELV circuits; basic insulation between hazardous voltage circuits and dead metal parts; and operational insulation within each individual circuit. 3.3 A co
34、nstruction other than as noted in 3.2 may also be covered by this Outline of Investigation if it complies with the insulation application requirements in 2.2.6 of UL 1950. 3.4 A relay that has been investigated in accordance with UL 508 and having basic insulation between the coil and contacts and b
35、etween input and output circuits (see 3.2(b) is considered to be in compliance with UL 1950 without any additional investigation. CONSTRUCTION 4 Spacings 4. I Spacings for operational insulation (for example, within hazardous voltage, ELV, or SELV circuits) need not be subject to further evaluation.
36、 COPYRIGHT Underwriters Laboratories Inc. Licensed by Information Handling Services COPYRIGHT Underwriters Laboratories Inc. Licensed by Information Handling Services STD-UL SUBJECT 50AB-ENGL 279Li H 7275775 Ob91551 bA4 AUGUST 31,1994 RELAYS USED IN INFORMATION TECHNOLOGY EQUIPMENT - SUBJECT 508B 7
37、4.2 Spacings for basic insulation (for example, between hazardous voltage and ELV circuits and between hazardous voltage circuits and dead metal parts) need not be subject to further evaluation. 4.3 Spacings for double and reinforced insulation (for example, between hazardous voltage and SELV circui
38、ts) shall comply with the applicable clearances noted in Tables 3 and 4, and the applicable creepage distances noted in Table 6 of UL 1950. The applicable clearances and creepage distances shall be those associated with a Pollution Degree 2 environment and Material Group Illb. Exception No. 1: The c
39、learance and creepage distance associated with a Pollution Degree I environment may be employed in an encapsulated construction. Exception No. 2: The applicable creepage distances may be those associated with a higher material group if a CTI rating higher than 175 is involved. See note 4 of Table 6
40、of UL 1950. Exception No. 3: A printed wiring board having a coating that complies with Subclause 2.9.5 of UL 1950 (such as a conformal coating that complies with the Standard for Polymeric Materials - Use in Electrical Equipment Evaluations, U1 746C), may have clearance and creepage distances in ac
41、cordance with Table 6 of UL 1950. Exception No. 4: As specified in Subclause 2.9.7 of UL 1950, a relay that is epoxy encapsulated need only comply with the through insulation requirements specified in Subclause 2.9.4 of UL 1950. Creepage and clearance distance requirements need not be applied within
42、 the encapsulation. The thermal cycling, humidity, and electric strength tests for compliance in Subclause 2.9.6 of UL 1950, and the visual inspection described in Subciause 2.9.7 of U1 7950 are to be conducted if the temperatures measured within the encapsulation exceed the thermal index of the enc
43、apsulation. 4.4 A barrier that is necessary to maintain isolation between the coil and contacts or between input and output circuits involving hazardous voltage and SELV circuits shall comply with the distance through insulation requirements for reinforced insulation as specified in Subclause 2.9.4
44、of UL 1950. Exception: An optical isolator that complies with the requirements for double-protection optical isolators in the Standard for Optical Isolators, UL 1577, and with a dielectric insulation voltage rating at least equivalent to the minimum required by UL 1950 for the application is conside
45、red to be in compliance with the requirement specified in 4.4. 4.5 The requirements for enclosed or hermetically sealed constructions contained in Subclause 2.9.6 of UL 1950 need not apply to relays. 5 Securement of Wiring and Parts 5.1 As specified in Subclause 2.3.8 of UL 1950, uninsulated wiring
46、and parts at a hazardous voltage shall be so located or guarded as to reduce the likelihood of accidental shorting to SELV circuits, for example by tools or test probes used by service personnel. 5.2 As specified in Subclause 4.3.9 of UL 1950, equipment shall be so constructed that if any wire, scre
47、w, nut, washer, spring, or similar part becomes loose or falls out of position, it cannot in normal use become so disposed that creepage distances or clearances over supplementary insulation or reinforced insulation are reduced to less than the required values. 5.3 Some examples of constructions tha
48、t comply with 5.2 are mechanically securing and then soldering leads to printed wiring boards, or the use of double crimp type pressure wire connectors or spot welding. COPYRIGHT Underwriters Laboratories Inc. Licensed by Information Handling Services COPYRIGHT Underwriters Laboratories Inc. License
49、d by Information Handling Services STD-UL SUBJECT 50B-ENGL 37711 E 7275795 Ob91552 510 8 RELAYS USED IN INFORMATION TECHNOLOGY EQUIPMENT - SUBJECT 5088 AUGUST 31,1994 6 Flammability of Materials 6.1 Polymeric materials used in a relay are considered to be in compliance with the flammability requirements specified in Subclauses 4.4.3.1 - 4.4.3.3 of UL 1950. PERFORMANCE 7 Electric Strength Test 7.1 Insulation breakdown shall not occur when a relay is subjected to the applicable test voltage noted in Table 18 of UL 1950. Exception: Circuits involving operational or basic insulation a