CLC TR 50481-2009 Recommendations on filters for shielded enclosures《屏蔽罩用过滤器的建议》.pdf

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1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI British StandardsWB9423_BSI_StandardColCov_noK_AW:BSI FRONT COVERS 5/9/08 12:55 Page 1Recommendations on filtersfor shielded enclosuresPD CLC/TR 50481:2009National forewordThis Published Document is

2、the UK implementation of CLC/TR 50481:2009.The UK participation in its preparation was entrusted by Technical CommitteeGEL/210, EMC - Policy committee, to Subcommittee GEL/210/12, EMC basic,generic and low frequency phenomena Standardization.A list of organizations represented on this committee can

3、be obtained onrequest to its secretary.This publication does not purport to include all the necessary provisions of acontract. Users are responsible for its correct application. BSI 2009ISBN 978 0 580 64194 7ICS 31.160; 33.100.10Compliance with a British Standard cannot confer immunity fromlegal obl

4、igations.This Published Document was published under the authority of theStandards Policy and Strategy Committee on 3 Ju 2009Amendments issued since publicationAmd. No. Date Text affectedBRITISH STANDARDPD CLC/TR 50481:2009ly1TECHNICAL REPORT CLC/TR 50481 RAPPORT TECHNIQUE TECHNISCHER BERICHT April

5、2009 CENELEC European Committee for Electrotechnical Standardization Comit Europen de Normalisation Electrotechnique Europisches Komitee fr Elektrotechnische Normung Central Secretariat: avenue Marnix 17, B - 1000 Brussels 2009 CENELEC - All rights of exploitation in any form and by any means reserv

6、ed worldwide for CENELEC members. Ref. No. CLC/TR 50481:2009 E ICS 33.100.10; 31.160 Supersedes R210-004:1999English version Recommendations on filters for shielded enclosures This Technical Report was approved by CENELEC on 2009-03-20. CENELEC members are the national electrotechnical committees of

7、 Austria, Belgium, Bulgaria, Cyprus, the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingd

8、om. PD CLC/TR 50481:2009CLC/TR 50481:2009 2 Foreword This Technical Report was prepared by the Technical Committee CENELEC TC 210, Electromagnetic compatibility (EMC). The text of the draft was submitted to vote in accordance with the Internal Regulations, Part 2, Subclause 11.4.3.2 (simple majority

9、) and was approved by CENELEC as CLC/TR 50481 on 2009-03-20. This document supersedes R210-004:1999. _ PD CLC/TR 50481:2009 3 CLC/TR 50481:2009 Contents 1 Scope . 4 2 Normative references . 4 3 Definitions . 4 4 General recommendations on filters 4 5 Insertion loss . 4 5.1 Insertion loss of filters

10、. 4 5.2 Insertion loss values . 5 6 Filter selection . 5 6.1 Choice of filter . 5 6.2 Power line filters . 6 6.3 Signal line filters (including telecom lines) 6 7 Electrical safety. 6 8 Installation of filters 7 Figures Figure 1 Filter insertion loss value ae(typical performance for shielded enclosu

11、res) 5 Figure 2 Filter installations schematic 7 PD CLC/TR 50481:2009CLC/TR 50481:2009 4 1 Scope This document was prepared to give users general advices on filtering solutions adopted in shielded enclosures. It is mainly a collection of hints derived from practical experience. This document is coor

12、dinated with EN 50147-1 and EN 50417-2. The document covers the frequency range DC to 40 GHz. The range above 40 GHz and up to 400 GHz is under consideration. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only

13、the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. IEC 60050(161), International Electrotechnical Vocabulary (IEV) Chapter 161: Electromagnetic compatibility CISPR 17:1981, Methods of measurement of the suppression cha

14、racteristics of passive radio interference filters and suppression components 3 Definitions For the purposes of this document, the terms and definitions given in CISPR 17:1981 apply. 4 General recommendations on filters To prevent interference or over-voltages from being fed into, or out of the shie

15、lded enclosure via lines, all lines passing through the shielding must be filtered. In many cases it is not only necessary to protect equipment from broadband interfering signals, but also to limit pulsed type interference (effects of lighting and any man made pulse type phenomena e.g. industrial pr

16、ocess). The filter shall not degrade the shielding attenuation of the shielded enclosure. Filters that meet the requirements of the referenced specification below should not be retested after installation because the testing of filters is done in 50 system and shielding is a measure of transmission

17、loss performed with antennas. If cables that penetrate a shielded enclosure cannot be filtered, they shall have adequate shielding effectiveness and termination on both sides so as to avoid degradation of the shielding effectiveness of the whole installation. Filters are required at each point where

18、 an unshielded wire or cable passes through the shielding material of a shielded enclosure. This is to prevent uncontrolled transfer of electromagnetic energy into, or out of, shielded enclosure. 5 Insertion loss 5.1 Insertion loss of filters Practical experience has shown that the insertion loss va

19、lue of the filters shall be at least as great as the required shield attenuation values of the enclosure. The insertion loss of the filters shall be carefully selected keeping in mind that in the low frequency range (say 100 kHz), the interference is mainly propagated over lines (conducted interfere

20、nce). The shielding effectiveness of the filter housing shall not reduce that of the shielded enclosure. PD CLC/TR 50481:2009 5 CLC/TR 50481:2009 5.2 Insertion loss values The insertion loss of the filter is characterised by the lowest attenuation value recorded by three measuring circuits (balanced

21、, unbalanced, asymmetrical) described in CISPR 17. The specified insertion loss value shall be met with the full current load over the entire specified frequency range. During approval measurement of the shielded room, all the cabling of the filters should be noticed and taken into account during th

22、e measurement of the shielding attenuation of the enclosure, The filter is expected to attenuate all current lines and neutral by frequency dependent factor while the power frequency attenuation should approach zero. Signal filters shall behave in the same manner as above and particular attention is

23、 to be paid to the low band, pass band and high band (e.g. of shielded cables). Measurement configuration B3 and B4 of CISPR 17. Figure 1 Filter insertion loss value ae(typical performance for shielded enclosures) 6 Filter selection In the case of filters with current compensated chokes, steps shoul

24、d be taken to ensure that the outgoing and return lines are routed through the same filter. If artificial mains networks (according to EN 55016 series) or coupling/decoupling networks for immunity tests are installed in shielded rooms, the use of filters with current compensated chokes is not recomm

25、ended, because of saturation of the core. A considerable reactive current flows in that artificial network and does not ensure compensation of the current in the chokes. In these cases filters with non-saturated coils shall be used. Balanced telecommunications lines shall be routed via a special fil

26、ter. 6.1 Choice of filter Basic designs are available for power, control and telecommunications filters: filter to suppress interference Interference suppression filters are configured as reflective low pass filters, i.e. they always reach their maximum stop band attenuation if they are mismatched t

27、o the impedance of the interfering source or interfering sink, as well as the line impedance; filter to suppress over voltage Over voltage protection filters are configured using non linear devices, e. g. gas arrestors SVP (surge voltage protector), varistors and suppression diodes TAZ (= Transient

28、Absorption Zener), for which the switching characteristics (speed, threshold level are fundamental to the function of the filter). Both filters may be combined. PD CLC/TR 50481:2009CLC/TR 50481:2009 6 6.2 Power line filters The user of the enclosure determines his filter requirements in terms of pow

29、er frequency and current rating, any power line filter for DC, 50 Hz, 60 Hz and 400 Hz (or any other required frequency) supply shall be used within its specification. Line filters at higher frequencies (max. 400 Hz) may also be used for lower frequency applications. The current rating of the filter

30、 should always be higher than the maximum operating current. 6.3 Signal line filters (including telecom lines) A signal line filter shall be adequate for the application (e.g. correct pass band, for example: Fire protection system). 7 Electrical safety For safety reasons all metallic parts of the sh

31、ield must be connected to protective earth. The relevant parts of HD 60364 series, Low-voltage electrical installations, should be observed. All RF suppressor filters contain a continuous line for the protective earth (PE) conductor. The PE conductor is in contact with the housing, although the filt

32、er housing is fixed on the shielded wall and is in good electrical contact with it. Safety reasons require that it will be connected to the ground bolt of the shielded wall via a conductor from the ground terminal of the RF suppressor filter. The protective ground is connected to the ground bolt. Po

33、wer line filter may have high leakage current adequate protection may be ensured using a combination of ELCB (Earth leakage circuit breaker) and transformer. In certain cases isolation of the shield from the host building is necessary. To meet this requirement care must be taken that no electrical c

34、onnection exists between the shield and conductors like metal reinforcing bars in concrete walls, gas and water supply tubes, ground conductors of fluorescent lamps outside the shielded room, and other metallic materials. In this case it is essential that the ground connection of the entire shieldin

35、g structure is made at one, carefully selected point (single point grounding. Moreover for EMC reasons it is also essential, that this ground connection has an impedance as low as possible and is frequently checked. PD CLC/TR 50481:2009 7 CLC/TR 50481:2009 Figure 2 Filter installations schematic 8 I

36、nstallation of filters Whenever possible, the filters shall be bonded directly to the shield and shall be located in close proximity to each other. The bond impedance shall be as low as practicable. If the bonding is established by conduit between the shielded enclosure and the filters, then the con

37、duit shall be metal with welded seam or equivalent and the connection of the conduit to the filter and the shielding shall be welded, soldered or bolted to achieve the lowest practicable bon impedance. In the case of filters with current compensated chokes, the appropriate steps should be taken to e

38、nsure that the outgoing and return lines are routed through the same filter. Protective ground (minimum 16 mm2) PD CLC/TR 50481:2009CLC/TR 50481:2009 8 Bibliography EN 50147-1, Anechoic chambers Part 1: Shield attenuation measurement EN 50147-2, Anechoic chambers Part 2: Alternative test site suitab

39、ility with respect to site attenuation EN 55016-1 series, Specification for radio disturbance and immunity measuring apparatus and methods (CISPR 16-1 series) HD 60364 series, Low-voltage electrical installations (IEC 60364 series, mod.) PD CLC/TR 50481:2009This page deliberately left blankBSI is th

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