BRITISH STANDARD AUTOMOBILE SERIES BS AU 88a 1985 (Superseding BS AU 88 1965) Recommendations for ratings for light duty cables for automobile use UDC 629 113 066 621 315 3 021 BS AU 88a 1985 This Bri[.]
BRITISH STANDARD AUTOMOBILE SERIES BS AU 88a:1985 (Superseding BS AU 88:1965) Recommendations for ratings for light duty cables for automobile use UD C 62 1 66: 62 BS AU 88a:1985 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Automobile Standards Committee (AUE/- ) to Technical Committee AUE/1 6, upon which the following bodies were represented: Association of Trailer Manufacturers Department of Transport (Highways) Electric Cable Makers’ Confederation National Caravan Council Limited Society of Motor Manufacturers and Traders Limited This British Standard, having been prepared under the direction of the Automobile Standards Committee, was published under the authority of the Board of BSI and comes into effect on 28 June 985 © BSI 02- 2000 The following BSI references relate to the work on this standard: Committee reference AUE/1 Draft for comment 84/71 81 DC ISBN 580 14507 Amendments issued since publication Amd No Date of issue Comments BS AU 88a:1985 Contents Page Committees responsib le © BSI 02 - 000 Inside front cover Foreword ii Scope Recommended ratings Appendix A Guidance for designers Figure — Increase or decrease in rating with temperature Tab le — Recommended ratings for single cab les for automobile use i BS AU 88a: 985 Fore word This British Standard has been prepared under the direction of the Automobile Standards Committee It is a revision of BS AU 88: 965, which is withdrawn BS AU 88: 965 calculated the current rating of a cable on the basis of a current density factor which was used as a multiplier with the nominal conductor cross- sectional area This approach did not take into account various insulating materials which are used in present day cables, which give the possibility of similar conductor sizes being run at different temperatures depending upon the thermal rating of the insulation material The recommendations in this edition permit the user to rate a cable according to the end use and the thermal performance of the insulation A British Standard does not purport to include all the necessary provisions of a contract Users of British Standards are responsible for their correct application C omp liance with a British S tand ard d oe s no t of itse lf confe r immunity from le gal ob ligatio ns S ummary of p age s This document comprises a front cover, an inside front cover, pages i and ii, pages to and a back cover This standard has been updated (see copyright date) and may have had amendments incorporated This will be indicated in the amendment table on the inside front cover ii © BSI 02- 2000 BS AU 88a:1 985 Scope This British Standard gives recommendations for nominal current ratings of light duty cab les for automob ile use for conductor sizes in the range mm °C rise of NO TE to mm based on a temperature in the conductor Attention is drawn to Appendix A which gives guidance for designers Recommended ratings The recommended current ratings for single cab les are given in Table Table — Recommended ratings for single cables for automobile use Nominal Number and Maximum Nominal cross-sectional diameter of resistance current area wires at 20 ° C rating (plain copper) mm Strands/mm Ì m /m A 7/0 64 7/0 37 11.0 6/0 39 11.0 9/0 34 11.0 65 9/0 3 0 75 4/0 2 9/0 3 32 /0 4/0 84 9/0 /0 21 9/0 32 21 1.0 1.5 2 8/0 42 9/0 37 95 35/0 54 9/0 41 9 37/0 32 33 44/0 33 56/0 71 39 37/0 37 60 39 65/0 06 42 84/0 3 50 97/0 72 55 0/0 2 63 0 80/0 82 70 © BSI 02 - 000 BS AU 88a: 985 Ap p e ndix A Guidance for de signers Nominal current rating gives a rise in temperature of 30 °C above ambient in free air Increases or decreases in rating due to variations in ambient temperature, or use of insulants with higher temperature capabilities may be determined from Figure In order that the maximum conductor temperature obtained does not exceed the maximum rated temperature of the insulation, the permitted temperature rise due to current rating should always be calculated in relation to the maximum ambient temperature to which any part of the cable may be exposed in service De-rating of up to 50 % should be applied to a cable which is bunched with others in a harness (this 50 % de-rating is based on consideration of all the cables in a harness carrying full rated current simultaneously) Where cables are installed in an enclosed condition, a de-rating factor of 80 % of the full rating should be applied Proper care should be exercised regarding voltage drop, surface temperature, short-circuit capacity, mechanical strength and effect of temperature on adjacent components in selection of particular size of cable A A A A A The actual resistance per metre, R, of a cable in use can be calculated by using the following formula: R = R20 [1 + 0.00393 (T – 20)] where is the resistance per metre at 20 °C; R20 T is the operating temperature of cable, i.e ambient and rise due to current loading (in °C); 0.00393 is the temperature coefficient of resistance of copper at 20 °C The voltage drop, V, of a cable in use can be calculated by using the following formula: V= I × R × L where R is the resistance per metre of the cable at the operating temperature as obtained in ; I is the circuit current (in A); L is the length of the cable (in m) The value will be expressed in millivolts if R is expressed in milliohms per metre A A A © BSI 02-2000 BS AU 88a:1985 Figure — Increase or decrease in rating with temperature © BSI 02 - 000 BS AU 88a:1985 BSI — British Standards Institution BS I is the indep endent national b ody res p ons ib le for p rep aring Britis h S tandards It p res ents the UK view on s tandards in E urop e and at the international level It is incorp orated b y Royal C harter Revisions Britis h S tandards are up dated b y amendment or revis ion Us ers of Britis h S tandards should make s ure that they p oss es s the latest amendments or editions It is the constant aim of BS I to imp rove the quality of our p roducts and services We would b e grateful if anyone finding an inaccuracy or amb iguity while us ing this Britis h S tandard would inform the S ecretary of the technical committee res p ons ib le, the identity of which can b e found on the inside front cover Tel: 02 89 96 90 00 Fax: 02 89 96 40 BS I offers memb ers an individual up dating s ervice called PLUS which ens ures that s ub s crib ers automatically receive the lates t editions of s tandards Buying standards O rders for all BS I, international and foreign s tandards p ub lications s hould b e addres s ed to C us tomer S ervices Tel: 899 00 Fax: 899 7001 In res p ons e to orders for international standards , it is BS I p olicy to sup p ly the BS I imp lementation of thos e that have b een p ub lis hed as Britis h S tandards, unless otherwis e requested Information on standards BS I p rovides a wide range of information on national, E urop ean and international standards through its Lib rary and its Technical H elp to E xp orters S ervice Various BS I electronic information s ervices are also availab le which give details on all its p roducts and s ervices C ontact the Information C entre Tel: 02 89 96 71 1 Fax: 02 89 96 048 S ub s crib ing memb ers of BS I are kep t up to date with s tandards develop ments and receive sub s tantial discounts on the p urchase p rice of s tandards For details of thes e and other b enefits contact Memb ership Adminis tration Tel: 02 89 96 70 02 Fax: 02 89 96 00 Copyright C op yright s ub s is ts in all BS I p ub lications BS I als o holds the cop yright, in the UK, of the p ub lications of the international s tandardization b odies E xcep t as p ermitted under the C op yright, D es igns and Patents Act 988 no extract may b e rep roduced, s tored in a retrieval s ystem or transmitted in any form or b y any means – electronic, p hotocop ying, recording or otherwis e – without p rior written p ermis s ion from BS I This does not p reclude the free us e, in the cours e of imp lementing the standard, of necess ary details such as s ymb ols, and size, typ e or grade designations If thes e details are to b e used for any other p urp os e than imp lementation then the p rior written p ermiss ion of BS I must b e ob tained If p ermis sion is granted, the terms may include royalty p ayments or a licensing agreement D etails and advice can b e ob tained from the C op yright Manager BS I 89 C his wick H igh Road London W4 4AL Tel: 02 89 96 70