Iec ts 62997 2017

I E C TS 62 9 ® Edition 201 7-06 TE C H N I C AL S P E C I F I C ATI ON colour i n sid e I n d u s tri al el e ctroh eati n g an d el ectrom ag n e ti c proces si n g eq u i pm en t – IEC TS 62997:201 7-06(en) E val u ati on of h azard s cau s ed b y m ag n eti c n e arfi el d s from H z to M H z T H I S P U B L I C AT I O N I S C O P YRI G H T P RO T E C T E D C o p yri g h t © I E C , G e n e v a , S wi tz e rl a n d All rights reserved Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either IEC or IEC's member National Committee in the country of the requester If you have any questions about I EC copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or your local I EC member National Committee for further information IEC Central Office 3, rue de Varembé CH-1 21 Geneva 20 Switzerland Tel.: +41 22 91 02 1 Fax: +41 22 91 03 00 info@iec.ch www.iec.ch Ab ou t th e I E C The I nternational Electrotechnical Commission (I EC) is the leading global organization that prepares and publishes I nternational Standards for all electrical, electronic and related technologies Ab o u t I E C p u b l i ca ti o n s The technical content of IEC publications is kept under constant review by the IEC Please make sure that you have the latest edition, a corrigenda or an amendment might have been published I E C Catal og u e - webstore i ec ch /catal og u e The stand-alone application for consulting the entire bibliographical information on IEC International Standards, Technical Specifications, Technical Reports and other documents Available for PC, Mac OS, Android Tablets and iPad I E C pu bl i cati on s s earch - www i ec ch /search pu b The advanced search enables to find IEC publications by a variety of criteria (reference number, text, technical committee,…) It also gives information on projects, replaced and withdrawn publications E l ectroped i a - www el ectroped i a org The world's leading online dictionary of electronic and electrical terms containing 20 000 terms and definitions in English and French, with equivalent terms in additional languages Also known as the International Electrotechnical Vocabulary (IEV) online I E C G l os sary - s td i ec ch /g l oss ary 65 000 electrotechnical terminology entries in English and French extracted from the Terms and Definitions clause of IEC publications issued since 2002 Some entries have been collected from earlier publications of IEC TC 37, 77, 86 and CISPR I E C J u st Pu bl i s h ed - webstore i ec ch /j u stpu bl i sh ed Stay up to date on all new IEC publications Just Published details all new publications released Available online and also once a month by email I E C C u stom er S ervi ce C en tre - webstore i ec ch /csc If you wish to give us your feedback on this publication or need further assistance, please contact the Customer Service Centre: csc@iec.ch I E C TS 62 9 ® Edition 201 7-06 TE C H N I C AL S P E C I F I C ATI ON colour i n sid e I n d u s tri al el ectroh eati n g an d el ectrom ag n e ti c proce s si n g e q u i pm e n t – E val u ati on of h azard s cau s ed b y m ag n eti c n earfi el d s from H z to M H z INTERNATIONAL ELECTROTECHNICAL COMMISSION ICS 25.1 80.1 ISBN 978-2-8322-4449-4 Warn i n g ! M ake s u re th a t you ob tai n ed th i s p u b l i cati on from an au th ori zed d i stri b u tor ® Registered trademark of the International Electrotechnical Commission –2– I EC TS 62997: 201 © I EC 201 CONTENTS FOREWORD I NTRODUCTI ON Scope 1 Norm ative references 1 Terms, definitions, symbols and abbreviated term s 1 Terms and definitions 1 Quantities and units 4 Organisation and use of the technical specification 5 The basic relationship for determ ination of the in situ induced electric field 6 Requirements related to immediate nerve and m uscle reactions 6 General 6 Method using the conductor geom etry and current restriction (CGCR) Volunteer test m ethod Volunteer basic test method Method based on volunteer tests and sim ilarity with pre-existing scenario 3 Method based on volunteer tests, using available elevated conductor current or shorter distance between the conductor and bod ypart Method using m agnetic nearfield reference levels (RLs) Requirements related to bod y tissue overheating General I nterm ittent conditions wi th minutes tim e integration 20 I nterm ittent conditions in fingers and hands with shorter integration times 21 Calculations and num erical computations of induced E field and SAR by magnetic nearfields: inaccuracies, uncertainties and safety factors 21 Principles for handling levels of safety – general 21 The C value variations wi th B field curvature 22 Location of parts of the bod y, instrum entation and measurement issues 22 Handling of inaccuracies of in s itu E field and SAR num erical values 22 Approaches to com pliance 23 General 23 Cases where verification of levels being below the RL is sufficient 23 Cases where onl y B flux measurem ents are sufficient 23 Cases where the volunteer test method is applicable 23 5 Cases where the CGCR m ethod is applicable 23 Cases where num erical modelling is carried out 24 Summ ary of inaccuracy/uncertainty factors to be considered 24 Risk group classification and warning marking 24 General 24 I nduced electric fields from H z to kH z 25 I nduced electric fields from kH z to 00 kH z 25 I nduced electric fields from 00 kH z to MH z 25 Magnetic flux fields from H z to MH z 25 Warning m arking 25 Annex A (inform ative) Survey of basic restrictions, reference levels in other standards, etc 27 I EC TS 62997: 201 © I EC 201 –3– A Basic restrictions – general and deviations 27 A The coupling values C in I CNI RP guidelines and I EEE standards 27 A Basic restrictions – im mediate nerve and m uscle reactions 28 A Basic restrictions – specific absorption rates (SAR) 29 A Reference levels – external magnetic B field 29 Annex B (norm ative) Anal ytical calculations of magneticall y induced internal E field phenomena 30 B Som e basic formulas – m agnetic fields and Laws of Nature 30 B I nduced field deposition in tissues by magnetic nearfields 31 B Coupling of a hom ogeneous B field to hom ogeneous objects with simple geometries 31 B Starting points for numerical modelling 32 B 4.1 Relevant bod yparts 32 B 4.2 The use of external B field and internal power density in num erical modelling 32 Annex C (norm ative) Reference obj ects representing parts of the bod y: tissue conductivities 33 C Reference bod yparts 33 C General 33 C The wrist/arm m odels 33 C The hand m odel with tight fingers 33 C The hand m odel with spread-out fingers 33 C The finger m odel 33 C Dielectric properties of hum an tissues 33 C General data for assessments 33 C 2 I nner parts of the bod y 34 C Skin data 34 Annex D (inform ative) Results of num erical m odelling with objects in a H elm holtz coil and at a long straight conductor 35 D General and a large H elm holtz coil scenario with a diameter 200 mm sphere – FDTD 3D m odelling 35 D Other reference objects in the H elmholtz coil – FDTD 3D modelling 36 D The scenario 36 D 2 Numerical m odelling results with sm aller spheres 36 D Numerical results with other objects 37 Annex E (inform ative) Num erical FDTD modelling with objects at a long straight wire conductor 38 E Scenario and general inform ation 38 E Two 200 mm diam eter spheres 39 E The hand model with tight fingers at different distances from the wire – FDTD modelling 40 E 3.1 General inform ation and scenario 40 E 3.2 Modelling results – power deposition patterns 40 E The hand model with tight fingers at 00 mm from the wire – Flux® FEM modelling 42 E Coupling data and anal ysis for the hand m odel with tight fingers above the wire – FDTD m odelling 42 E Coupling data and anal ysis for the wrist/arm model above the wire 43 Annex F (informative) Num erical modelling and volunteer experiments with the hand models at a coil 45 F.1 General and on the B field amplitude 45 –4– I EC TS 62997: 201 © I EC 201 F.2 The hand model with tight fingers mm , mm , mm and 50 mm above the coil and with its right side above the coil axis – FDTD m odelling 46 F The scenario 46 F 2 Modelling results 47 F.3 The hand model with tight fingers mm above the coil and with variable position in the x direction – FDTD m odelling 51 F.4 The hand model with spread-out fingers, mm straight above the coil – FDTD modelling 51 F.5 The hand model with tight fingers near a coil with m etallic workload – FDTD modelling 52 F.6 The finger model mm above the coil – FDTD numerical modelling 54 F The scenarios 54 F Modelling results 54 F.7 Analysis of the FDTD modelling results 56 F General 56 F With the hand m odel 56 F With the finger m odel 56 F.8 Volunteer studies 56 F General 56 F Calculations of the induced electric field strength in F 57 F.9 Comparisons with conventional electric shock effects by contact current 57 F.1 Conclusions from the data in Annexes E and F 58 F 1 Coupling factor C data in relation to reference obj ect geometries and magnetic flux characteristics without workload 58 F Coupling factor C m odifications by workloads 58 F Rationales for the CGCR basic value with the volunteer m ethod 58 Annex G (informative) Some exam ples of CGCR values of a hand near conductors as function of frequency, conductor current and configuration 60 G.1 Frequency and conductor current relationships: adopted CGCR value 60 G.2 A hand above a thin wire 60 G.3 A hand above a coil 61 Annex H (inform ative) Frequency upscaling with num erical m odelling 64 H General and energ y penetration depth 64 H Actual penetration depth data 64 H The penetration depth issue of representativity wi th frequency upscaling 65 H Separation of the internal power density caused by direct capacitive coupling, and that caused by the external m agnetic field 65 H The frequency upscaling procedures 66 H General 66 H Choices of conductivity and control procedures 66 Bibliograph y 68 Figure – Exam ples of warning m arking 26 Figure A – I CNI RP, I EEE and 201 3/35/EU basic restrictions (RMS) 28 Figure D.1 – The z-directed magnetic field m omentaneous maximal amplitude in the central y plane of the H elmholtz coil with the conductive 200 mm diam eter sphere 36 Figure D.2 – The power density patterns in the central y plane (left) and central z (equatorial) plane of the 200 mm diameter sphere 36 Figure D.3 – The power density patterns in the central z plane of the reference obj ects, with maximal C values in m 37 I EC TS 62997: 201 © I EC 201 –5– Figure E – Long straight wire scenario 38 Figure E – Power deposition patterns in the central z planes of the two spheres at mm and 20 m m away from the sphere axis; σ = 20 Sm –1 39 Figure E – Power deposition pattern in the central y plane of the sphere at mm distance from the wire axis; σ = 20 Sm –1 39 Figure E – Scenario with the hand model above the wire axis 40 Figure E – Power density in the hand model 2, mm above the wire axis 40 Figure E – Power density in the hand m odel mm above the wire axis 41 Figure E – Power density in the hand model 00 mm above the wire axis 41 Figure E – Current density in the central cross section of the hand model at mm from the wire – Flux® FEM modelling 42 Figure E – Wrist/arm model above a long straight wire 43 Figure E – Linear power density (left, power scaling) and electric field amplitude (linear scale) in the x plane of wrist/arm model mm straight above a long straight wire 43 Figure F – I llustration of the B field at a single turn coil, with the coil centre at the left margin of the im age – Flux® FEM modelling 45 Figure F – H and above the coil scenario 46 Figure F – Power density pattern in the central vertical plane and in the bottom mm layer of the hand m odel, z = mm above the top of the coil; a = –51 m m 47 Figure F – Power density pattern in the central vertical plane and in the bottom mm layer of the hand model, z = mm ; a = –51 mm 47 Figure F – Power density pattern in the central vertical plane and in the bottom mm layer of the hand model, z = 50 m m; a = –51 mm 48 Figure F – The ± x-directed (left im age) and ±y-directed m omentaneous maximal E field at the hand underside, z = mm; a = –51 mm 49 Figure F – The local power density pattern of the condition in Figure F 3, showing the m m × mm voxel size and the mm integration region mm above the hand underside 50 Figure F – The local y-directed m om entaneous m aximal electric field pattern of the condition in Figure F 3, showing the mm × mm voxel size and the m m integration region mm above the hand underside 50 Figure F – The power density pattern in the hand model centred above the coil and m m above it; left im age: bottom region, right image: mm up 51 Figure F – The hand model with spread-out fingers located mm straight above the coil (left); relative power densities at the height of maximum power density between fingers (right) 51 Figure F 1 – The hand model mm above the coil and a 00 m m diameter m etallic workload in the coil 52 Figure F – Quiver plot of the m agnetic ( H) field am plitude in logarithmic scaling, in the scenario in Figure F 1 with a non-m agnetic (left) and magnetic (right) workload 52 Figure F – The power density pattern in the central vertical cross section in the hand scenario in Figure F 1 53 Figure F – The power density in the central vertical cross section of the hand as in the scenario in Figure F 1 , but 50 mm above the coil; with no workload (left) and with perm eable metallic workload (right) 53 Figure F – The two finger positions above the coil; left = y - directed finger 54 Figure F – Power density maximum pattern in the y-directed mm diameter finger model 54 Figure F – Power density maximum pattern in the x-directed mm diameter finger model 55 –6– I EC TS 62997: 201 © I EC 201 Figure F – M omentaneous maximal electric field m aximum pattern in the x-directed mm diam eter finger model 55 Figure F – Plastic plate above the coil 57 Figure G – Allowed RMS current at 1 kH z, based on CGCR = 40 Vm –1 60 Figure G – CGCR coil currents at 1 kH z for the hand m odel with the side at the coil axis, at various heights above the coil 62 Figure G – CGCR coil currents at 1 kH z for the hand m odel at mm above the coil with different sideways positions 63 Table C – Examples of dielectric data of hum an tissues at normal bod y tem perature 34 Table E – Coupling factors for the hand m odel with tight fingers at various heights above the wire axis 42 Table G – Coupling factors and allowed coil currents at 1 kH z for the hand m odel with the side at the coil axis, at various heights above the coil 61 Table G – Coupling factors and allowed coil currents at 1 kH z for the hand m odel at mm above the coil with different sideways positions 62 I EC TS 62997: 201 © I EC 201 –7– INTERNATI ONAL ELECTROTECHNI CAL COMMISSI ON I N D U S T RI AL E L E C T RO H E AT I N G AN D E L E C T RO M AG N E T I C P RO C E S S I N G E Q U I P M E N T – E va l u a ti o n o f h a z a rd s c a u s e d b y m a g n e ti c n e a rfi e l d s fro m H z to M H z FOREWORD ) The I nternati on al Electrotechni cal Comm ission (I EC) is a worl d wid e organization for stan dardization com prisin g all n ation al el ectrotechnical comm ittees (I EC National Comm ittees) The object of I EC is to prom ote internati onal co-operation on all q uestions concerni ng stand ardi zati on in the el ectrical an d electronic fi elds To this en d and in additi on to other acti vities, I EC pu blish es I nternational Stan dards, Techn ical Specificati ons, Technical Reports, Publicl y Avail abl e Specificati ons (PAS) an d Gu ides (h ereafter referred to as “I EC Publication(s)”) Th ei r preparation is entrusted to tech nical comm ittees; any I EC N ational Comm ittee interested in the subj ect dealt with m ay partici pate in this preparatory work I nternational, governm ental an d n on governm ental organ izations l iaising with th e I EC also participate i n this preparation I EC collaborates closel y with the I ntern ational Organi zation for Stand ardization (I SO) in accordance with ditions determ ined by agreem ent between th e two organi zati ons 2) The form al decisions or ag reem ents of I EC on tech nical m atters express, as n early as possible, an i nternati onal consensus of opi nion on the rel evant subjects since each technical com m ittee has representati on from all interested I EC N ational Com m ittees 3) I EC Publications have the form of recom m endations for intern ational use an d are accepted by I EC National Com m ittees in that sense While all reasonable efforts are m ade to ensure that the tech nical content of I EC Publications is accu rate, I EC cann ot be h eld responsi ble for th e way in which th ey are used or for an y m isinterpretation by an y en d u ser 4) I n order to prom ote intern ational u niform ity, I EC National Com m ittees und ertake to apply I EC Publications transparentl y to the m axim um extent possible i n their national an d regi on al publicati ons Any d ivergence between an y I EC Publication and the correspondi ng national or regi on al publicati on sh all be clearl y in dicated in the latter 5) I EC itself d oes n ot provi de an y attestation of conform ity I n depend ent certificati on bodies provi de conform ity assessm ent services and, in som e areas, access to I EC m arks of conform ity I EC is not responsi bl e for an y services carri ed out by ind ependent certification bodi es 6) All users shou ld ensure that th ey have the l atest editi on of thi s publicati on 7) No liability shall attach to I EC or its directors, em ployees, servants or ag ents inclu din g in divi dual experts an d m em bers of its technical com m ittees and I EC Nati on al Com m ittees for any person al i njury, property d am age or other dam age of any nature whatsoever, wheth er di rect or indirect, or for costs (includ i ng leg al fees) and expenses arisi ng out of the publ ication, use of, or relian ce upon, this I EC Publicati on or any other I EC Publications 8) Attention is drawn to th e N orm ative references cited in th is publ ication Use of the referenced publ ications is indispensable for the correct applicati on of this publication 9) Attention is drawn to the possibility that som e of the elem ents of this I EC Publication m ay be the su bject of patent rig hts I EC shall not be held responsibl e for identifyi ng any or all such patent ri ghts The main task of I EC technical comm ittees is to prepare I nternational Standards I n exceptional circumstances, a technical committee may propose the publication of a technical specification when • • the required support cannot be obtained for the publication of an I nternational Standard, despite repeated efforts, or the subj ect is still under technical development or where, for an y other reason, there is the future but no imm ediate possibility of an agreem ent on an I nternational Standard Technical specifications are subj ect to review within three years of publication to decide whether they can be transformed into I nternational Standards I EC TS 62997, which is a technical specification, has been prepared by I EC technical committee 27: I ndustrial electroheating and electrom agnetic processing –8– I EC TS 62997: 201 © I EC 201 The text of this technical specification is based on the following documents: Enqui ry draft Report on votin g 27/1 000A/DTS 27/1 007/RVDTS Full inform ation on the voting for the approval of this technical specification can be found in the report on voting indicated in the above table This docum ent has been drafted in accordance with the I SO/I EC Directives, Part I n this technical specification, the following print types are used: • term s used throughout this specification which have been defined in Clause 3: in bold type The com mittee has decided that the contents of this document will remain unchanged until the stability date indicated on the I EC website under "http: //webstore iec.ch" in the data related to the specific docum ent At this date, the document will be • • • • reconfirmed, withdrawn, replaced by a revised edition, or amended A bilingual version of this publication m ay be issued at a later date I M P O R T AN T th at it – Th e ' co l ou r i n s i d e' tai n s u n d e rs t a n d i n g c o l o u r p ri n t e r of c o l o u rs i ts wh i c h c o n te n ts l og o a re U s e rs on th e co ve r p ag e o f th i s c o n s i d e re d sh ou l d to t h e re fo re be p u b l i c a ti o n u s e fu l p ri n t th i s fo r i n d i c ate s th e d o cu m en t c o rre c t u sin g a – 58 – F F.1 0.1 C o n c l u s i o n s fro m t h e d a t a i n C o u p l i n g fa c t o r C I EC TS 62997: 201 © I EC 201 An n e x e s E a n d F d a t a i n re l a t i o n t o re fe re n c e o b j e c t g e o m e t ri e s a n d m ag n eti c fl u x c h a c t e ri s t i c s w i t h o u t w o rk l o a d • • • • • • • Results with the Helm holtz coil, representing the farfield and thus not in principle covered by this Technical Specification, show very good agreement with the basic theory C = π R for the sphere and long circular cylinder cases For objects with flat geom etry such as the hand with tight fingers, the C values can i n crease b y a factor abou t ½ i n certai n m ag n eti c fi el d fi g u rati on s wi th c urvature com parable to the largest dim ension of the object This is explained in Clause E.5 The C diminishes by a factor at very short distances, typicall y less than about mm, between the wire axis and the nearest obj ect side Generall y, the C value referring to the at the bod ypart where the m axim um induced electric fields occurs primaril y depends on the bod ypart circum ference along a path perpendicular to the direction of the m agnetic flux For homogeneous flux C becomes half the circum ference, in m etre Exam ples are given in Figure D with object data in Annex C The C value is significantl y reduced in an inhom ogeneous magnetic flux As an example, C ≈ 0,25 m for the hand m odel with tight fingers in a hom ogeneous flux, but about times less at mm distance from a straight wire; see Figure E and Figure E The larger hand with tight fingers has about the same m aximal C value in a homogeneous flux as has the sm aller hand with spread-out fingers Com paring C at the using Ccoil at coils for the hand m odels in the m ost onerous location does not give a higher Ccoil value than CPOI in a homogeneous flux; see Figure G and Figure G cou p l i n g POI POI F.1 0.2 • • • va l u e C o u p l i n g fa c t o r C m o d i fi c a t i o n s b y w o rk l o a d s A non-perm eable workload in a coil does not significantl y influence the magnetic flux outside the coil projection in its axial direction, but does so with a perm eable workload; see Figure F and other data in Figure F An axi al l y l on g perm eabl e workload i n a coil wi l l exten d th e fl ux axi al l y at i ts peri ph ery, i n creasi n g th e Ccoil (based on an em pty coil) value for a bod ypart al ong the workload; see Figure F A perm eable workload ending in a coil will reduce the effective diam eter of the flux, resulting in the pattern being as if from a smaller coil and resulting in a reduced Ccoil (based on an em pty coil) value com pared with empty coil; see Figure F and data in Figure F F.1 0.3 Ra t i o n a l e s fo r t h e C G C R b a s i c v a l u e w i t h t h e v o l u n t e e r m e t h o d The I CNI RP and EU BR value at 1 kH z is 2, V· m –1 and the I EEE BR value is Vm –1 • The volunteers with onerousl y located hands with spread-out fingers on the plastic plate sensed a tingling above perception but not at the level Using the E field factor between perception and one can set the level of perception to about 00 Vm –1 , including a margin for computational, model and other sources of error The level of perception for touch currents becomes about 40 V· m –1 and that of 75 Vm –1 as calculated from volunteer studies and data in I EC TS 62996 The modelled and experimental result 00 Vm –1 for the hand as computed from the data in Clause D is 2, tim es higher than that for contact current perception, and , tim es higher than that for contact current The difference for the hand can largel y be explained by the particular pattern of the E field; see N ote in and Figure F and Figure F a v e rs i o n a v e rs i o n • • a v e rs i o n a v e rs i o n • I EC TS 62997: 201 â I EC 201 ã ã ã 59 – The fact that there was no perception in the finger alone is explained by the lower Ccoi l values of about 0, 09 m There is clearl y a discrepancy between the touch/contact current specification of perception and the BR values of in situ E field BRs The latter obviousl y contain safety factors stem ming from hazard considerations which are onl y partiall y applicable to induced E fields by magnetic nearfields The comparative methods for the coil exam ple in Annex F are all consistent and clearl y indicate that there are in practice no hazards with coils of this size with the very high current 4, kA, which is in practice the highest possible current l evel in an efficientl y watercooled conductor of this size H owever, a safety factor is appropriate, so the reference for CGCR is set to 40 Vm –1 at 1 kH z This results in the CGCR current in the case of a hand very close to and straight above the coil in Clauses F and F to becom e about 2, kA at 1 kH z This is then below the level of perception NOTE Th e C valu e for the han d m odel in a h om ogen eous as shown i n Fig ure D B field perpendicul ar to its flat sides is about 0, 25 m , NOTE Fu rther CGCR data for oth er scen arios are provid ed in Ann ex G – 60 – I EC TS 62997: 201 © I EC 201 Annex G (informative) Some examples of CGCR values of a hand near conductors as function of frequency, conductor current and configuration G.1 Frequency and conductor current relationships: adopted CGCR value The exam ples in Annex G are derived from data described in Annexes E and F, and additional numerical modelling The coupling factor C being independent of the frequency is im portant, and with the linear frequency proportionality of the basic restriction on induced electric field shown in Figure A results in the allowed conductor current being inversel y proportional to the frequency As a consequence a reference sinusoidal frequency can be set This is chosen to be 1 kH z, as in the voluntary studies in Clause F As specified in 2, a CGCR value is applicable instead of BR values as specified by I CNI RP, EU and I EEE, and is set to 40 Vm –1 at 1 kH z, as generalised in Formula (1 ) for other frequencies NOTE The cases with n on -m agn etic an d m agn etic workloads in the coi l d ealt with in Cl ause F and F are not dealt with i n Ann ex G I n form ation and req uirem ents on m agnetic shield ing can be found i n Cl ause of I EC 6051 9-1 : 201 G.2 A hand above a thin wire The data in Table E are used to create the graph in Figure G Formulas (1 ) and (B 2) then give the allowed CGCR current I in A RMS as I = 3,64 × ρ C (G.1 ) Where ρ is the radial distance from the wire axis to the nearest facing flat surface of the hand model as shown in Figure E All owed RMS current at 1 kH z, kA 00 10 1 10 00 Flat hand side distance from thin wi re axis (m m ) IEC Figure G.1 – Allowed RMS current at 1 kHz, based on CGCR = 40 Vm –1 I EC TS 62997: 201 © I EC 201 G.3 – 61 – A hand above a coil The coil specified in Clause F was used (1 37 mm outer diam eter, mm height and mm width of a superconductor) The operating frequency was MH z The B field at the coil centre was 5, µT The Ccoil values, i e those with the B value at the coil centre rather than at an y part of the hand are given in Table G.1 , for several hand heights and the sideways position x =-51 m m (i e the hand side at the coil axis) NOTE The fol lowing d ata i m ply that coil currents exceedin g kA wil l be allowed under m ost practical circum stances of bod yparts cl ose to th e coil Such hi gh currents i n a reason abl y sm all cross section coil, at this freq uency, is not technically feasible since even forced intern al watercoolin g of the coil tu be becom es insufficient, and l oss of cool ing will th en cause an im m ediate vi olent destruction Table G.1 – Coupling factors and allowed coil currents at 1 kHz for the hand model with the side at the coil axis, at various heights above the coil Distance from the wire axis to the underside of the object Ccoil in E maximum location Al lowed coil cu rrent at 1 kHz (m ) (A) (mm ) 0, 201 ‡ 0, 96 † 075 0, 96 † 0, 75 ‡ 075 0, 88 † 0, 55 ‡ 50 20 0, 36 975 50 0, 068 950 00 0, 024 1 800 †: At hand l on g side ‡: At hand u ndersid e Using Form ulas (1 ) and (B 3) with the coil data gives I = 455 / Ccoil (A) The data in Table G are illustrated in the graph in Figure G (G 2) – 62 – I EC TS 62997: 201 © I EC 201 Allowed RMS current at 1 kH z, kA, based on 40 V/m m ax intern al el ectric field stren gth 00 10 1 10 00 Han d m odel distance above th e coil (m m ) IEC Figure G.2 – CGCR coil currents at 1 kHz for the hand model with the side at the coil axis, at various heights above the coil Table G.2 – Coupling factors and allowed coil currents at 1 kHz for the hand model at mm above the coil with different sideways positions Horizontal position a of hand centre (see Fig F.2) Left hand edge posi tion Ccoil in E maximum location Al lowed coil current at 1 kHz (m) (mm ) (kA) –1 At leftm ost coil top surface 0, 083 850 –81 With right hand sid e 30 mm left of the coil axis 0, 1 3 575 –51 With right hand sid e above coil axis 0, 88 50 –21 With right hand sid e 30 mm right of the coil axis 0, 238 700 With hand straight above the coil 0, 251 625 The quite high Ccoil value for the hand straight above the coil should be similar to that with the hand in a hom ogeneous m agnetic field in the sam e direction as the m ain field by the coil C = 0, 25 m in Figure D 3, so the agreem ent is very good I EC TS 62997: 201 © I EC 201 – 63 – Allowed RMS current at 1 kH z, kA, based on 40 V/m m ax intern al el ectric field stren gth 500 000 500 000 500 000 Sam e as mm height in Fi gu re G2 500 000 500 000 –1 25 –1 00 –75 –50 Han d hori zontal centre d istance from coil axis (m m ) –25 IEC Figure G.3 – CGCR coil currents at 1 kHz for the hand model at mm above the coil with different sideways positions – 64 – I EC TS 62997: 201 © I EC 201 An nex H (informative) Frequency u pscali n g with nu meri cal m odell i ng H.1 General an d energ y penetrati on depth Objects with a very high conductivity will possess the skin effect – a lim itation of energ y penetration – with alternating fields This results in inner parts being m ore or less shielded by the outer The skin depth is where the field strength is reduced to /e I n ph ysics, the power penetration depth dp in m is used instead, and is half the skin depth At dp the power flux density is /e of that at the surface, and /e of the power that rem ains below it For the ideal situation of a halfspace of the material irradiated by a plane wave, the exact formula becom es λ dp = − π × Im [ m (H ) ] ε where λ is the free space wavelength in m and ε the complex relative perm ittivity ε′ – jε ″ with ε ′ being the real permittivity ("dielectric constant") and ε ″ the dielectric loss factor dp is a sufficient approximation also for nearfields The conductivity σ recalculated to ε″ becomes dp = ,8 1 × (H 2) σ f For frequencies below MH z, no other contributions to ε ″ than by a largel y frequencyindependent ionic conductivity are typicall y assumed but deviations exist; see the Gabriel et a l publications referred to in the Bibliograph y The ε ′ value is typicall y quite high (see Annex C) due to various capacitive layer and cellular effects The simplified Formulas for dp and σ if the dp ε′ influence is insignificant are 252 = σ ⋅ and thus 6,33 -4 ⋅ σ = f f dp [m] (H 3) [Sm –1 ] (H 4) ⋅ H.2 Actual penetrati on depth data Using Formula (H ) one obtains dp 252 mm at MH z and = Sm –1 At 00 kH z dp becom es tim es larger (i e 2, m) and if at still 00 kH z is instead 0, Sm –1 , dp becomes 0,2 times still larger, i.e 5, m σ ≈ σ Since onl y a part of the bod y being present in the nearfield and not wholebod y exposure is considered here, it is concluded that in practice no penetration depth limitation exists for frequencies lower than about MH z, but may so for higher operating frequencies, at which an y recalculation for frequency upscaling for m odelling must be made with care I EC TS 62997: 201 © I EC 201 H.3 – 65 – The penetration depth issue of representativity with frequency upscaling Formula (H 3) results in decreases of dp with both increasing frequency and increasing conductivity As a consequence, dp cannot be m ade too small at the upscaled frequency, compared with data at the actual frequency Onl y nearfield situations are considered They are characterised by a decay of the external B field intensity away from the source, except very close to sources characterised by a large "active surface" region, such as coils and parallel conductors at a significant distance from each other a) With a sm all bod ypart (hand or finger) close to the source, dp at an upscaled frequency can be quite short b) With a large bod ypart (head, torso, leg) close to the source, the B field intensity and by that the induced E intensity is largest in the nearest bod ypart and will decay by the "edd y current circular effect" to becom e very small in centre regions Furthermore, the B intensity decay with distance away from the source above will reduce the induced E field intensity in the rear regions of the object I n general and in consideration of acceptable m argins of accuracy (i e safety factors) a characteristic thickness of the bod ypart, D of maxim all y times dp is acceptable, so: , D < 2· dp H.4 • • • (H 5) Separation of the internal power density caused by direct capacitive coupling, and that caused by the external magnetic field A very high ε ″ – in the order of several tim es 000 – is needed for good separation Clear indications are needed of the com bined phenomena of the creation of a capacitive current between the conductor and the object, and the resulting time-harmonic charge redistribution by the conductivity of the obj ect These indications are a very shallow (1 mm thick or less) and distinct power density pattern, with m inimum in the nearest region of the obj ect to the electric field source I f only the coupli ng valu e C in the m ost affected region is sought for, one can set high value: ,8 ⋅ 01 σ f > σ to a very 50 000 [s Ω –1 m –1 ] (for very good discrimination) (H.6) However, this can result in too low power densities in inner regions of the object Additional numerical m odelling runs with lower ε ″ can therefore be necessary, for establishing a good result with respect to the overall m agneticall y induced electric field in the object The dipolar polarisation effects have then to be observed The lowest acceptable ε ″ will of course depend on the overall scenario, but at least applies in m ost cases This provides an important relationship between σ and f i e ε″ ≈ 000 , ,8 ⋅ 01 σ f > 000 [ s Ω –1 m –1 ] (for acceptably sm all external E field influence) ( H ) I f an obj ect with high effective perm ittivity is thin, its film resistance R f in ohm s per square becom es important This is – 66 – I EC TS 62997: 201 © I EC 201 σd (H 8) Rf = I f this becom es comparable with the free space wave impedance Z0 ≈ 377 Ω there will be a substantial power absorption in the film of the external E field as well as a distortion by the first dipole field effect As a consequence of this, num erical two-dimensional m odelling cannot represent the real ph ysical world H.5 H.5.1 The frequency upscaling procedures General As described in I EEE C95 -201 0, section 2, frequency upscaling is necessary for low frequencies when using numerical FDTD m odelling m ethods These suffer from the need to com pl y with a stability criterion which requires short tim esteps which at some hundred kH z typicall y becom e impracticall y m an y per cycle with regard to CPU tim e The number of tim esteps per cycle needed for stationary conditions to be created is inversel y proportional to the frequency, and the sm allest necessary voxel sizes of som e few millimetres are independent of the frequency FDTD m ethods typicall y have an important advantage over finite elem ent (FEM) methods in the d ynamic range of field am plitudes Such large d ynam ic ranges are needed with modelling of e g induction system s and with other scenarios with a very large range of field amplitudes The B field can be very strong in the workload treatm ent section and decays very quickl y as a nearfield away from that section Additionall y, very low induced E field and SAR are allowed in hum an bod yparts in comparison with the process data in the workload Modern comm erciall y available FDTD software contains advanced ABC (absorbing boundary condition) options suitable also for scenarios with sizes much smaller than a free space wavelength H owever, accurate sim ulation of free space conditions around in particular the excitation regions in practice require additional circumferential absorbing means; see Clauses E and H The basic frequency scaling factor results in the induced E field amplitude at constant B amplitude (and thus constant source current) being proportional to the frequency The obtained E value is divided by the fhi gh / flow factor in the recalculations after the modelling The bod y tissue conductivity is frequency dependent and the quotient between that at flow and the value used in the m odelling at fhig h is also to be used in the recalculation when the SAR is sought for H.5.2 Choices of conductivity and control procedures The conditions of Formulas (H 5) and (H 7) are adhered to in the selection of the upscaled frequency in FDTD m odelling Since they are contradictory, an interactive procedure is normall y applied The typical procedure is to firstl y use the actual conductivity values at the prelim inary upscaled frequency, for checking with Form ula (H 7); the value should preferabl y be > 000 Sm -1 for the lowest conductivity The highest conductivity is then tested with Form ula (H 5); if the combined parts of the body now all with that conductivity are < dp no changes of an y conductivity is needed at the upscaled frequency Conductivities of all parts of the bod y are to be increased with an equal factor if Formula (H 6) is not fulfilled I f Formula (H 5) is not fulfilled or when the condition in Formula (H 6) is needed for separation of the capacitively induced power deposition pattern, the first alternati ve is to run the scenario an yway, to see which parts of the bod y get the highest E value I EC TS 62997: 201 © I EC 201 – 67 – A second m ethod is to run a Helm holtz coil scenario with the possibly too high conductivities and look at the B field (stationary or at its second maxim um in time); if this is constant over the whole set of bod yparts, Formula (H 5) is fulfilled – 68 – I EC TS 62997: 201 © I EC 201 Bibliography I EC 60050 (all parts), http://www electropedia org) I EC 60050-1 61 : 990, In te rn a tion a l In te rn a tion a l Ele ctrote ch n ica l Ele ctrote ch n ica l (available Voca b ula ry Voca b ula ry – at Ch a p te r 61 : Ele ctrom a gn e tic com p a tib ility I EC 60050-841 , In te rn a tion a l Ele ctro te ch n ica l Voca b ula ry – Pa rt 84 : In dustria l e le ctro h e a t I EC 60050-903: 201 3, IEC TS 60479-2, In te rn a tio n a l Ele ctrote ch n ica l Voca b ula ry – Pa rt 903: Risk a ss e ssm e n t Effe cts of curre n t on h um a n b e in gs a n d live s tock – Pa rt 2: Sp e cia l a s p e cts IEC 6051 (all parts), Sa fe ty in in s ta lla tion s for e le ctroh e a tin g and e le ctrom a gn e tic proce ss in g IEC 6051 9-6: 201 , Sa fe ty in e le ctro h e a t in s ta lla tio n s – Sp e cifica tio n s for sa fe ty in in dustria l m icro wa ve h e a tin g e quip m e n t IEC 6051 9-9: 2005, Sa fe ty in e le ctro h e a t in s ta lla tion s – Pa rt 9: Pa rticula r re quire m e n ts fo r h igh -fre que n cy die le ctric h e a tin g in sta lla tio n s IEC 61 40: 201 6, Prote ction a ga in s t e le ctric sh ock – Co m m o n a s p e cts fo r in s ta lla tio n s and equip m e n t IEC 621 0, Ele ctric a n d m a gn e tic fie ld le ve ls ge n e te d b y A C p o we r syste m s – Me a sure m e n t p roce dure s with re ga rd to p ub lic e xp osure I EC 62209-2, Hum a n e xp os ure to dio fre que n cy fie lds fro m wire le ss com m un ica tio n de vice s – Hum a n m o de ls, Proce dure to de te rm in e th e sp e cific h a n d-h e ld a n d b o dy-m o un te d in s trum e n ta tio n , a b s orp tio n te (SA R) for a n d p roce dure s – Pa rt 2: wire le ss co m m un ica tio n de vice s us e d in clos e p ro xim ity to th e h um a n b ody (fre que n cy n ge o f 30 MHz to G Hz) IEC 62226-2-1 , Exp os ure to e le ctric or m a gn e tic fie lds in th e low a n d in te rm e dia te fre que n cy n ge – Me th ods for ca lcula tin g th e curre n t de n sity a n d in te rn a l e le ctric fie ld in duce d in th e h um a n b o dy – Pa rt 2-1 : Exp os ure to m a gn e tic fie lds – 2D m o de ls I EC 62479: 201 0, e quip m e n t with A ss e s sm e n t th e b a s ic of th e re strictio n s co m p lia n ce re la te d to of low- p owe r h um a n e xp osure e le ctron ic to and e le ctrica l e le ctro m a gn e tic fie lds (1 MHz to 300 G Hz) I EC 62822-2: 201 6, Ele ctric we ldin g e quip m e n t – A sse ssm e n t o f re strictio n s re la te d to h um a n e xp osure to e le ctro m a gn e tic fie lds (0 Hz to 300 G Hz) – Pa rt 2: A rc we ldin g e quip m e n t I EC TS 62996: – In dustria l e le ctro h e a tin g and e le ctro m a gn e tic p ro ce ss in g e quip m e n t – Re quire m e n ts o n to uch curre n ts, vo lta ge s a n d e le ctric fie lds fro m kHz to MHz Directive 201 3/35/EU on the minimum health and safety requirements regarding the exposure of workers to the risks arising from ph ysical agents (electrom agnetic fields), J une 201 Gabriel S et al, The dielectric properties of biological tissues: I Literature survey; Ph ys Med Biol No 41 996, p 2231 -2249 _ Under preparati on Stag e at th e tim e of publicati on: I EC/ADTS 62996: 201 I EC TS 62997: 201 © I EC 201 – 69 – Gabriel S et al, The dielectric properties of biological tissues: I I Measurem ents in the frequency range H z to 20 GH z; Ph ys M ed Biol N o 41 996, p 2251 -2269 I CNI RP 998 (I nternational Com mission on N on-I onizing Radiation Protection), Guidelines for lim iting exposure to tim e ‐ varying electric, magnetic and electrom agnetic fields (up to 300 GH z) health ph ysics 74 (4): 494-522; 998 (available at http: //www icnirp org ) ICNI RP: 2006, www icnirp org ICNI RP: 2008, ICNIRP sta te m e n t G uide lin e s fo r on lim itin g e le ctro m a gn e tic fie lds (up to 300 G Hz) , I CNI RP: 201 0, G uide lin e s for lim itin g fa r in fra re d e xp osure to dia tio n tim e - va ryin g available at www icnirp org e xp o sure to tim e -va ryin g available at e xp o sure ) , e le ctric, e le ctric and m a gn e tic m a gn e tic and fie lds (1 Hz to 00 kHz) , available at www icnirp org I EEE C95 : 2005, IEEE sta n da rd for sa fe ty le ve ls with re sp e ct to h um a n e xp osure to dio fre que n cy e le ctro m a gn e tic fie lds, kHz to 300 GHz, I EEE C95 a: 201 0, A m e n dm e n t : Sp e cifie s available at www standards.ieee org ce ilin g lim its for in duce d a n d co n ta ct curre n t, cla rifie s dis tin ctio n s b e twe e n loca lis e d e xp osure a n d sp a tia l p e a k p o we r de n s ity, a va ila b le a t www s ta n da rds ie e e org I EEE C95 -201 0, Ele ctric, Ma gn e tic, IEEE Re co m m e n de d Pra ctice and Ele ctro m a gn e tic Fie lds for Me a s ure m e n ts with Re s p e ct to and Hum a n Co m p uta tion s Exp o sure to of Such Fie lds , Hz to 00 kHz I EEE C95.6: 2002, IEEE sta n da rd fo r sa fe ty le ve ls with re s p e ct to h um a n e xp osure to e le ctro m a gn e tic fie lds , 0–3 kHz, a va ila b le a t www sta n da rds ie e e org EN 50444:2008, B a sic sta n da rd for th e e va lua tion o f h um a n e xp osure to e le ctro m a gn e tic fie lds fro m e quip m e n t fo r a rc we ldin g a n d a llie d p roce sse s EN 50445: 2008, re s ista n ce Pro duct we ldin g, a rc fa m ily we ldin g sta n da rd and a llie d to de m o n stra te p roce sse s with co m p lia n ce th e b a sic of e quip m e n t re strictio n s for re la te d to h um a n e xp os ure to e le ctrom a gn e tic fie lds (0 Hz – 300 GHz) I talian N ational Research Council I nstitute of Applied Ph ysics “N ello Carrara”, Florence I tal y, Ca lcula tio n s 00 GHz of th e die le ctric p ro p e rtie s of b o dy tiss ue s in th e fre que n cy , freel y available at http: //ni remf ifac cnr it/tissprop/h tmlclie/htmlcli e php Kanai H et al, n ge 10 Hz – Hum a n b ody im p e da n ce fo r e le ctrom a gn e tic h a za rd a n a lys is in th e VF to MF b a n d; IEEE MTT-32 No 984 , p 763– 772 _ INTERNATIONAL ELECTROTECHNICAL COMMISSI ON 3, rue de Varembé PO Box 31 CH-1 21 Geneva 20 Switzerland Tel: + 41 22 91 02 1 Fax: + 41 22 91 03 00 info@iec.ch www.iec.ch