CLC/TR 50481:2009
(Main)Recommendations on filters for shielded enclosures
Recommendations on filters for shielded enclosures
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 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.
Priporočila za filtre zaslonjenih prostorov
General Information
Overview
CLC/TR 50481:2009 - "Recommendations on filters for shielded enclosures" is a CENELEC technical report giving practical guidance on selecting, installing and testing filters used where cables and conductors penetrate electromagnetic shielded enclosures. The report is coordinated with EN 50147-1 and EN 50417-2 and covers the frequency range DC to 40 GHz (with higher bands under consideration). It compiles field‑proven recommendations for EMC performance, safety and installation practices.
Key topics and technical requirements
- Scope and frequency range: Guidance applies from DC up to 40 GHz; extension to 40–400 GHz is under consideration.
- Filtering requirement: All lines penetrating the shield must be filtered or have adequate shielding and termination to avoid degrading the enclosure’s shielding attenuation.
- Insertion loss: Filter insertion loss should be at least equal to the required shielding attenuation of the enclosure. Specified insertion loss is the lowest attenuation obtained from three CISPR 17 measurement circuits (balanced, unbalanced, asymmetrical) and must be met at full current load across the specified frequency range.
- Filter types and selection:
- Power line filters: selected for correct current rating and power frequency (DC, 50/60/400 Hz, etc.); filter current rating must exceed maximum operating current.
- Signal/telecom filters: choose according to pass‑band and application (e.g., fire protection, balanced telecom lines need special filters).
- Over‑voltage protection: may use nonlinear surge devices (gas arrestors, varistors, suppression diodes); suppression and reflective low‑pass designs can be combined.
- Choke considerations: For current‑compensated chokes, route outgoing and return conductors through the same filter. Avoid compensated chokes where large reactive currents (e.g., artificial mains networks per EN 55016) can saturate cores; use non‑saturating coils instead.
- Installation and bonding: Filters should be bonded directly to the shield with the lowest practicable bond impedance - welded/soldered/bolted metal conduits and connections are recommended.
- Safety and grounding: All metallic shield parts must be connected to protective earth; RF suppressors include a continuous PE conductor and must be grounded to the shield’s ground bolt. Consider single‑point grounding and low impedance ground checks where necessary.
Applications and users
- EMC test laboratory and anechoic/ shielded room designers and operators
- Facility and installation engineers implementing shielded enclosures for radiated and conducted immunity/emission testing
- System integrators deploying sensitive telecom, medical, defence or measurement equipment requiring controlled EMI environments
- Safety and compliance engineers responsible for grounding, leakage current mitigation and surge protection
Related standards
- CISPR 17 (measurement circuits and suppression characteristics)
- EN 50147-1 / EN 50147-2 (anechoic chambers, shield attenuation/site attenuation)
- EN 55016 series (artificial mains / measuring apparatus)
- HD 60364 (low‑voltage electrical installation safety)
Keywords: shielded enclosures, filters, insertion loss, EMC, shielding attenuation, power line filters, signal line filters, protective earth, CENELEC.
Frequently Asked Questions
CLC/TR 50481:2009 is a technical report published by CLC. Its full title is "Recommendations on filters for shielded enclosures". This standard covers: 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 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.
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 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.
CLC/TR 50481:2009 is classified under the following ICS (International Classification for Standards) categories: 31.160 - Electric filters; 33.100.10 - Emission. The ICS classification helps identify the subject area and facilitates finding related standards.
You can purchase CLC/TR 50481:2009 directly from iTeh Standards. The document is available in PDF format and is delivered instantly after payment. Add the standard to your cart and complete the secure checkout process. iTeh Standards is an authorized distributor of CLC standards.
Standards Content (Sample)
SLOVENSKI STANDARD
01-september-2009
1DGRPHãþD
SIST CLC/R 210-004:2000
3ULSRURþLOD]DILOWUH]DVORQMHQLKSURVWRURY
Recommendations on filters for shielded enclosures
Ta slovenski standard je istoveten z: CLC/TR 50481:2009
ICS:
31.160 (OHNWULþQLILOWUL Electric filters
33.100.10 Emisija Emission
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
TECHNICAL REPORT
CLC/TR 50481
RAPPORT TECHNIQUE
April 2009
TECHNISCHER BERICHT
ICS 33.100.10; 31.160 Supersedes R210-004:1999
English 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 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 Kingdom.
CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
Central Secretariat: avenue Marnix 17, B - 1000 Brussels
© 2009 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. CLC/TR 50481:2009 E
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) and was approved by CENELEC as CLC/TR 50481 on
2009-03-20.
This document supersedes R210-004:1999.
________________
– 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 . 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 (typical performance for shielded enclosures) . 5
e
Figure 2 – Filter installations schematic . 7
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 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.
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 measurement 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 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 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 Ω system and shielding is
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 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,
...
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