1、BRITISH STANDARDBS EN 3475-418:2007Aerospace series Cables, electrical, aircraft use Test methods Part 418: Thermal endurance for conductorsThe European Standard EN 3475-418:2007 has the status of a British StandardICS 49.060g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g
2、48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g54g3g51g40g53g48g44g55g55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58BS EN 3475-418:2007This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 December 2007 BSI 2007ISBN 978 0 580 55950 1Nat
3、ional forewordThis British Standard is the UK implementation of EN 3475-418:2007.The UK participation in its preparation was entrusted by Technical Committee ACE/6, Aerospace avionic electrical and fibre optic technology, to Panel ACE/6/-/2, Aerospace Cables.A list of organizations represented on th
4、is committee 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.Compliance with a British Standard cannot confer immunity from legal obligations.Amendments issued since
5、 publicationAmd. No. Date CommentsEUROPEAN STANDARDNORME EUROPENNEEUROPISCHE NORMEN 3475-418November 2007ICS 49.060English VersionAerospace series - Cables, electrical, aircraft use - Testmethods - Part 418: Thermal endurance for conductorsSrie arospatiale - Cbles lectriques usagearonautique - Mthod
6、es dessais - Partie 418: Endurancethermique des conducteursLuft- und Raumfahrt - Elektrische Leitungen frLuftfahrtverwendung - Prfverfahren - Teil 418: ThermischeGebrauchsdauer fur LeiterThis European Standard was approved by CEN on 21 June 2007.CEN members are bound to comply with the CEN/CENELEC I
7、nternal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the CEN Management Centre or to any CEN me
8、mber.This European Standard exists in three official versions (English, French, German). A version in any other language made by translationunder the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as theofficial versions.CEN members
9、 are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,Romania, Slovakia, Slovenia, Spain, Sweden, Switz
10、erland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMIT EUROPEN DE NORMALISATIONEUROPISCHES KOMITEE FR NORMUNGManagement Centre: rue de Stassart, 36 B-1050 Brussels 2007 CEN All rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN 3
11、475-418:2007: E2 Contents Page Foreword3 1 Scope 4 2 Normative references 4 3 Introduction4 3.1 General4 3.2 Theory .4 3.3 Technical consequences on conductors 5 4 Preparation of specimens.5 4.1 Specimens 5 4.2 Conditioning.5 4.3 Initial measurement .5 5 Apparatus .5 6 Method 6 7 Requirements.6 EN 3
12、475-418:20073 Foreword This document (EN 3475-418:2007) has been prepared by the Aerospace and Defence Industries Association of Europe - Standardization (ASD-STAN). After enquiries and votes carried out in accordance with the rules of this Association, this Standard has received the approval of the
13、 National Associations and the Official Services of the member countries of ASD, prior to its presentation to CEN. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by May 2008, and conflicting nationa
14、l standards shall be withdrawn at the latest by May 2008. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN and/or CENELEC shall not be held responsible for identifying any or all such patent rights. According to the CEN/CENELEC
15、 Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembour
16、g, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. EN 3475-418:20074 1 Scope This standard specifies a test method to value the thermal endurance of bi-metal conductors, by valuation of the influence of metallic migration
17、on the electrical resistance per unit length. It shall be used together with EN 3475-100. 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
18、 of the referenced document (including any amendments) applies. EN 3475-100, Aerospace series Cables, electrical, aircraft use Test methods Part 100: General. EN 3475-301, Aerospace series Cables, electrical, aircraft use Test methods Part 301: Ohmic resistance per unit length. 3 Introduction 3.1 Ge
19、neral Various bi-metal conductors exist among which the most usual are tin-coated copper, copper clad steel and copper clad aluminium. Inter-metallic compounds may appear at the interface of the various layers of such conductors. As these compounds have generally an increasing growth rate when expos
20、ed to elevated temperature, the characteristics of the cables (mechanical and electrical) can be affected depending on the time and the temperature of exposure. A good example is tin-coated copper where the diffusion of tin into copper is a fast, well-known and important phenomenon between ambient t
21、emperature and 230 C. 3.2 Theory The inter-metallic layer formation at the interface of the various layers in the wires is due to a diffusion mechanism in association with solubility phenomenon. The diffusion rate is characterized by a coefficient of diffusion of the two metals in contact at a given
22、 temperature. This coefficient of diffusion has generally the form of an Arrhenius law and is given by the formula. TRQeDoD.= where R is the ideal gas constant; Q is the activation energy for the diffusion process; and T is the absolute temperature; Do is a constant given for a couple of diffusion.
23、EN 3475-418:20075 Furthermore, in the case of the electrical wires, the calculation shows that there is a relation between the coefficient of diffusion D and the time t of exposure at different temperatures: D.t = Const So that D1.t1 = D2.t2 This say that it is possible to calculate an equivalent ti
24、me of exposure at a higher temperature but this must be done at a temperature for which the solubility limit and the metallurgic mechanisms involved are not too different, generally in a domain below 280 C. If the test temperature is too high there is a risk of obtaining a degradation mechanism not
25、representative of reality. For example, on a copper clad aluminium conductor to assess the behaviour for: 10 000 hours at 180 C, a test of 2 200 hours at 200 C can be performed; 140 000 hours at 150 C, a test of 2 500 hours at 200 C can be performed. 3.3 Technical consequences on conductors When app
26、eared, such inter-metallic compounds will affect the mechanical and electrical behaviour of the conductor. Even if all these characteristics do not evolve proportionally in relation with its thickness, it has been shown that an easy way to survey the growth of the inter-metallic part is to measure t
27、he increase of the linear resistance. 4 Preparation of specimens 4.1 Specimens A sufficient length shall be taken from the same batch of a finished cable. Generally, the test is run on gauge 20. 4.2 Conditioning This length shall not be bent with a radius less than 50 times the overall diameter of t
28、he cable, during temperature exposure. 4.3 Initial measurement On this initial length take a minimum length of three meters to make three samples of at least one meter, make three measurements of the electrical resistance per unit length, according to EN 3475-301. Record the arithmetic mean value, o
29、f this sampling corrected to 20 C, as the initial measurement without thermal ageing. NOTE The temperature correction coefficient is generally given in the relevant conductor product standard. 5 Apparatus An air-circulating oven shall be required for this test. Its size must be sufficient to hold al
30、l necessary specimens during the complete duration of the test. EN 3475-418:20076 6 Method The initial length shall be placed in the oven for the time and the temperature specified in the product standard. Each month, or specified period in the concerned product standard, after having cut 10 cm at t
31、he extremity, one specimen of three meters minimum length shall be removed from the oven and cooled for at least 1 h at ambient temperature. Then, make three samples of at least one meter and performed three measurements of the electrical resistance per unit length, according to EN 3475-301. Record
32、the arithmetic mean value as the value of the concerned sampling corrected to 20 C. All specimens shall be kept in order if necessary to be able to measure the thickness of the inter-metallic interface. 7 Requirements a) the electrical resistance increase of each mean measurement shall be less than
33、x % of the initial mean measurement. b) the electrical resistance increase of each mean measurement shall be less than y % of the maximum resistance requested in the product standard. x and y values shall be specified in the product standard. EN 3475-418:2007blankBS EN 3475-418:2007BSI389 Chiswick H
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