1、raising standards worldwide NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW BSI British Standards WB9423_BSI_StandardColCov_noK_AW:BSI FRONT COVERS 5/9/08 12:55 Page 1 Recommendations on filters for shielded enclosures PD CLC/TR 50481:2009National foreword This Published Docum
2、ent is the UK implementation of CLC/TR 50481:2009. The UK participation in its preparation was entrusted by Technical Committee GEL/210, EMC - Policy committee, to Subcommittee GEL/210/12, EMC basic, generic and low frequency phenomena Standardization. A list of organizations represented on this com
3、mittee can be obtained on request to its secretary. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. BSI 2009 ISBN 978 0 580 64194 7 ICS 31.160; 33.100.10 Compliance with a British Standard cannot confer immun
4、ity from legal obligations. This Published Document was published under the authority of the Standards Policy and Strategy Committee on 3 Ju 2009 Amendments issued since publication Amd. No. Date Text affected BRITISH STANDARD PD CLC/TR 50481:2009 ly 1 TECHNICAL REPORT CLC/TR 50481 RAPPORT TECHNIQUE
5、 TECHNISCHER BERICHT April 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 f
6、orm and by any means reserved 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 ele
7、ctrotechnical committees of 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, Switz
8、erland and the United Kingdom. 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, Subclaus
9、e 11.4.3.2 (simple majority) 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
10、 Insertion loss of filters . 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 a e(typical perf
11、ormance for shielded enclosures) 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 exper
12、ience. This document is coordinated 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.
13、 For dated references, only 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 measur
14、ement of the suppression characteristics 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
15、fed into, or out of the shielded 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
16、phenomena e.g. industrial process). 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 i
17、s a measure of transmission 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
18、required at each point where 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 show
19、n that the insertion loss value 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 ove
20、r lines (conducted interference). 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
21、measuring circuits (balanced, 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
22、taken into account during the 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
23、 and particular attention is 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 a e(typical performance for shielded enclosures) 6 Filter selection In the case of filters with current co
24、mpensated chokes, steps should 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 com
25、pensated chokes is not recommended, 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 shal
26、l be routed via a special filter. 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 attenua
27、tion if they are mismatched to 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 suppres
28、sion diodes TAZ (= Transient 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
29、 requirements in terms of power 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
30、 current rating of the filter 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
31、 all metallic parts of the shield 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 t
32、he housing, although the filter 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 con
33、nected to the ground bolt. Power 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
34、be taken that no electrical connection 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 conn
35、ection of the entire shielding 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 Filte
36、r installations schematic 8 Installation 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
37、and the filters, then the conduit 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 appropria
38、te steps should be taken to ensure that the outgoing and return lines are routed through the same filter. Protective ground (minimum 16 mm 2 ) 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
39、2: Alternative test site suitability 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 d
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