SIST EN 50444:2008

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Basic standard for the evaluation of human exposure to electromagnetic fields from equipment for arc welding and allied processesNorme de base pour l'évaluation de l'exposition des personnes aux champs électromagnétiques d'un équipement pour le soudage à l'arc et les techniques connexesGrundnorm zur Ermittlung der Exposition von Personen gegenüber elektromagnetischen Feldern von Einrichtungen zum Lichtbogenschweißen und artverwandten Prozessen25.160.10Varilni postopki in varjenjeWelding processes13.280Varstvo pred sevanjemRadiation protectionICS:SIST EN 50444:2008en,fr,deTa slovenski standard je istoveten z:EN 50444:200801-junij-2008SIST EN 50444:2008SLOVENSKI
STANDARD







EUROPEAN STANDARD EN 50444 NORME EUROPÉENNE
EUROPÄISCHE NORM February 2008
CENELEC European Committee for Electrotechnical Standardization Comité Européen de Normalisation Electrotechnique Europäisches Komitee für Elektrotechnische Normung
Central Secretariat: rue de Stassart 35, B - 1050 Brussels
© 2008 CENELEC -
All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 50444:2008 E
ICS 13.280; 25.160.10
English version
Basic standard for the evaluation of human exposure
to electromagnetic fields from equipment
for arc welding and allied processes
Norme de base pour l'évaluation
de l'exposition des personnes
aux champs électromagnétiques
d'un équipement pour le soudage à l'arc et les techniques connexes
Grundnorm zur Ermittlung der Exposition von Personen gegenüber elektromagnetischen Feldern von Einrichtungen zum Lichtbogenschweißen und artverwandten Prozessen
This European Standard was approved by CENELEC on 2008-02-01. CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CENELEC member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CENELEC member into its own language and notified to the Central Secretariat has the same status as the official versions.
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.



EN 50444:2008 – 2 – Foreword This European Standard was prepared by the Technical Committee CENELEC TC 26A, Electric arc welding equipment.
The text of the draft was submitted to the formal vote and was approved by CENELEC as EN 50444 on 2008-02-01. The following dates were fixed: – latest date by which the EN has to be implemented at national level by publication of an identical national standard or by endorsement
(dop)
2009-02-01 – latest date by which the national standards conflicting with the EN have to be withdrawn
(dow)
2011-02-01 This European Standard is to be read in conjunction with EN 50445. This European Standard has been prepared under mandates M/305 and M/351 given to CENELEC by the European Commission and the European Free Trade Association. __________



– 3 – EN 50444:2008 Contents 1 Scope.6 2 Normative references.6 3 Terms and definitions.6 3.1 General.6 3.2 Specific for arc welding and similar applications.8 4 Physical quantities, units and constants.9 4.1 Quantities and units.9 4.2 Constants.9 5 Assessment procedures.9 5.1 Arc welding equipment components to be tested.9 5.2 Assessment conditions.9 5.3 Averaging.9 5.4 Pulsed or non-sinusoidal welding current.9 5.4.1 General.9 5.4.2 Summation for basic restriction assessment.10 5.4.2.1 Summation of current density components without phase information.10 5.4.2.2 Summation of currents density components including phase information.10 5.4.2.3 Summation of specific absorption rate (SAR) components.11 5.4.3 Summation for reference level assessment.11 5.4.3.1 Summation for stimulation effects without phase information.11 5.4.3.2 Effective reference level method.12 5.4.3.3 Summation for stimulation effects including phase information.13 5.4.3.4 Summation for thermal effects.13 5.4.4 Equivalent frequency of induced current density waveforms.13 5.5 Conductivity of living tissue.14 5.6 Frequency range limitations.14 5.7 Application of assessment procedures.15 5.8 Measurements.16 5.8.1 Measuring equipment.16 5.8.2 Static field measurements.17 5.8.3 Time domain field measurements.17 5.8.4 Broadband field measurements.17 5.8.5 Frequency selective field measurements.17 5.8.6 Time domain weighted field measurements.18 5.9 Analytical calculations.18 5.9.1 General information.18 5.9.2 Derivation of magnetic field based on welding current.18 5.9.3 Derivation of induced current density based on magnetic field.19



EN 50444:2008 – 4 – 5.10 Numerical calculations.20 5.10.1 General information.20 5.10.2 Derivation of magnetic field.20 5.10.3 Derivation of current density using conductive disc models.20 5.10.4 Simulations based on anatomical body models.21 5.10.4.1 General information.21 5.10.4.2 Anatomical body models.21 5.10.4.3 Calculation methods.22 5.10.4.4 Position of the body model in relation to the welding cables.22 6 Uncertainty of assessment.22 6.1 Including uncertainty.22 6.1.1 General information.22 6.1.2 Shared uncertainty budget.22 6.1.3 Using uncertainty in comparison against limit values.23 6.2 Evaluation of uncertainties.23 6.2.1 Introduction.23 6.2.2 Individual uncertainties.23 6.2.3 Combined uncertainties.23 6.3 Reasonable overall uncertainties.23 6.4 Examples of typical uncertainties.24 7 Assessment report.25 7.1 General principles.25 7.2 Items to be recorded in the assessment report.25 Annex A (normative)
Assessment parameters.26 Annex B (informative)
Examples for exposure assessment.30 Annex C (informative)
Numerical simulation using anatomical body models.39 Annex D (informative)
Geometry factor and field gradients.43 Annex E (informative)
Welding current ripple assessment.44 Annex F (informative)
Summation using first order filter weighting functions.46 Annex G (informative)
Example for an uncertainty budget.50 Bibliography.51



– 5 – EN 50444:2008 Figures Figure 1 – Average electrical conductivities for homogeneous body modelling from 10 Hz to 10 MHz.14 Figure A.1 – Probe position for measurement on welding cables.27 Figure A.2 – Topology of welding cable for numerical simulations.28 Figure B.1 – Probe position during measurement.31 Figure B.2 – Planar current density distribution in the disk.32 Figure B.3 – Welding current waveform and calculation parameters.33 Figure B.4 – Induced current density derived from welding current.33 Figure B.5 – Spectral components of welding current pulse.34 Figure B.6 – Summation of induced current density components with phase information.35 Figure B.7 – Flux density waveform and r.m.s. values of the spectral components.35 Figure B.8 – Flux density waveform and r.m.s. values of the spectral components.36 Figure B.9 – Summation of flux density components with phase information.37 Figure B.10 – Flux density waveform and r.m.s. values of the spectral components.37 Figure D.1 – Planar field distribution for different cable arrangements at I2 = 200 A.43 Figure E.1 – Spectral analysis of triangular function.44 Figure F.1 – Magnetic flux density reference levels, filter and tabulated values.47 Figure F.2 – Weighting function phase angles for B and H, filter and tabulated values.47 Figure F.3 – Induced current density basic restrictions, filter and tabulated values.48 Figure F.4 – Weighting function phase angles for J, filter and tabulated values.49 Figure F.5 – Comparison of results for example B.7 (first order filter left, tabulated values right).49 Tables Table 1 – Permissible assessment procedures for arc welding equipment.15 Table 2 – Permissible assessment procedures for welding cables.16 Table 3 – Reasonable expanded assessment uncertainties.24 Table A.1 – Typical parameters for tests with pulsed welding current.26 Table B.1 – Induced current density components and phase angles.34 Table B.2 – Flux density components.35 Table B.3 – Flux density components and phase angles.36 Table B.4 – Flux density components and fractional contributions.38 Table C.1 – Electrical conductivity of tissue types.41 Table E.1 – J simulation results for relevant spectral components (r.m.s. values).45 Table E.2 – B calculation results for relevant spectral components (r.m.s. values).45 Table G.1 – Example uncertainty budget for broadband field measurement.50



EN 50444:2008 – 6 – 1 Scope This European Standard applies to equipment for arc welding and allied processes designed for use in industrial or domestic environments, including welding power sources, wire feeders and ancillary equipment, e.g. torches, liquid cooling systems and arc striking and stabilising devices. NOTE Allied processes are for example electric arc cutting and arc spraying. This standard specifies procedures for assessment of electromagnetic fields produced by arc welding equipment and defines standardized operating conditions and test set-ups. This standard may be used as a basis to demonstrate compliance to national and international guidelines or requirements with regard to human exposure to EMF from arc welding equipment [1] [2]. Other standards may apply to products covered by this standard. In particular this standard can not be used to demonstrate electromagnetic compatibility with other equipment; nor does it specify any product safety requirements other than those specifically related to human exposure to electromagnetic fields. 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. EN 50392
Generic standard to demonstrate the compliance of electronic and electrical apparatus with the basic restrictions related to human exposure to electromagnetic fields (0 Hz – 300 GHz) EN 50445
Product family standard to demonstrate compliance of equipment for resistance welding, arc welding and allied processes with the basic restrictions related to human exposure to electromagnetic fields (0 Hz – 300 GHz) EN 60974-1
Arc welding equipment – Part 1: Welding power sources
(IEC 60974-1) 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 General 3.1.1 basic restrictions restrictions on exposure to electric, magnetic and electromagnetic fields that are based directly on established health effects and biological considerations 3.1.2 conductivity (σ) ratio of the conduction current density in a medium to the electric field strength 3.1.3 contact current current flowing into the body by touching a conductive object in an electromagnetic field



– 7 – EN 50444:2008 3.1.4 effective reference level (BL,eff) level, provided for practical exposure assessment purposes using a broadband measurement, derived from frequency dependent reference levels considering the spectral content of the field 3.1.5 EMF electric, magnetic or electromagnetic field 3.1.6 exposure situation that occurs when a person is subjected to electric, magnetic or electromagnetic fields or to contact current other than those originating from physiological processes in the body and other natural phenomena 3.1.7 exposure level value of the quantity evaluated when a person is exposed to electromagnetic fields or contact currents 3.1.8 induced current density (J) electromagnetic field induced current per unit area inside the body 3.1.9 magnetic flux density (B) magnitude of a field vector that is equal to the magnetic field H multiplied by the permeability µ of the medium
B = µ H (1) 3.1.10 magnetic field strength (H) magnitude of a field vector in a point that results in a force Fr on a charge q moving with velocity vr
Fr = q (vrx µ Hr) (2)
or magnetic flux density divided by permeability of the medium 3.1.11 permeability (µ) property of a material which defines the relationship between magnetic flux density B and magnetic field strength H NOTE It is commonly used as the combination of the permeability of free space µ0 and the relative permeability µR for specific dielectric materials
µ = µR µ0
(3)
where
µ is the permeability of the medium expressed in Henry per metre (H m-1). 3.1.12 point of investigation (POI) location in space at which the value of E-field, H-field or power density is evaluated NOTE This location is defined in Cartesian, cylindrical or spherical co-ordinates relative to the reference point on the EUT.



EN 50444:2008 – 8 – 3.1.13 root-mean-square (r.m.s.) effective value or the value associated with joule heating, of a periodic electromagnetic wave NOTE The r.m.s. value is obtained by taking the square root of the mean of the squared value of a function.
Expression in time domain
∫=TdttXTX02r.m.s.)(1 (4) where X(t) is the signal at time t; T is the signal period or multiples of it. Expression in frequency domain
∑=nnXX2r.m.s. (5) where
Xn is the magnitude of spectral component at nth frequency, expressed as r.m.s. value. 3.1.14 reference levels directly measurable quantities, derived from basic restrictions, provided for practical exposure assessment purposes NOTE Respect of the reference levels will ensure respect of the relevant basic restriction. If the reference levels are exceeded, it does not necessarily follow that the basic restriction will be exceeded. 3.2 Specific for arc welding and similar applications 3.2.1 arc welding power source equipment for supplying current and voltage and having the required characteristics suitable for arc welding and allied processes NOTE 1 An arc welding power source may also supply services to other equipment and auxiliaries e.g. auxiliary power, cooling liquid, consumable arc welding electrode and gas to shield the arc and the welding area. NOTE 2 In the following text, the term “welding power source” is used. 3.2.2 industrial and professional use use intended only for experts or instructed persons 3.2.3 expert (competent person, skilled person) person who can judge the work assigned and recognize possible hazards on the basis of professional training, knowledge, experience and knowledge of the relevant equipment NOTE Several years of practice in the relevant technical field may be taken into consideration in assessment of professional training. 3.2.4 instructed person person informed about the tasks assigned and about the possible hazards involved in neglectful behaviour NOTE If necessary, the person has undergone some training.



– 9 – EN 50444:2008 3.2.5 rated maximum welding current (I2max) maximum value of the conventional welding current that can be obtained at the conventional welding condition from a welding power source at its maximum setting 4 Physical quantities, units and constants 4.1 Quantities and units The internationally accepted SI units are used throughout this document. Quantity Symbol Unit Dimension Current density J Ampere per square metre A m-2 Electric conductivity σ Siemens per metre S m-1 Frequency ƒ Hertz Hz Magnetic field strength H Ampere per metre A m-1 Magnetic flux density B Tesla T (Vs m-2) Permeability µ Henry per metre H m-1 4.2 Constants Physical Constant Symbol Magnitude Permeability of free space µ0 4π ⋅10-7 H m-1 5 Assessment procedures 5.1 Arc welding equipment components to be tested The main source of EMF is the welding current, delivered by the power source, flowing through the welding circuit. The parameters of the current e.g. amplitude and waveform, which are determined by the welding power source only, have the greatest influence on the exposure level. Therefore assessment shall be based on these parameters and the configuration of the welding circuit as specified in this standard. However, direct emissions from components of the welding system e.g. wire feeders may also contribute to the total EMF and shall be considered. Care shall be taken not to add emissions assessed at short distances (less than 1 m), as the welder will not be close to those components at the same time. 5.2 Assessment conditions Test configurations, distances, operating conditions and other parameters, which are valid for all evaluation procedures, are specified in Annex A. 5.3 Averaging Time and spatial averaging shall be made in accordance with the relevant document containing limits. 5.4 Pulsed or non-sinusoidal welding current 5.4.1 General For pulsed or non-sinusoidal (including a d.c. component) welding current a separate assessment for a.c. and d.c. components shall be made. Only the a.c. component shall be used to assess compliance with restrictions for time varying fields. The d.c. component shall be used to assess compliance with restrictions for static fields.



EN 50444:2008 – 10 – The a.c. component may consist of a number of spectral components, typically a fundamental frequency (e.g. the pulse repetition rate for a pulsed MIG process or the switching frequency for inverter power sources) and harmonics. These spectral components shall be summed for assessment of exposure, considering the biological effects caused by the individual components (e.g. stimulation effects in the frequency range from 1 Hz to 10 MHz and thermal effects in the frequency range above 100 kHz). Summation of frequency components causing stimulation and thermal effects shall be made separately. Summation procedures are given in 5.4.2 and 5.4.3. Different frequency ranges of the field (e.g. due to pulsed welding current or ripple current) may be evaluated separately. In this case the results of each evaluation shall be added linearly. Only spectral components up to the upper frequency defined in 5.6 shall be considered. Harmonic components with an amplitude of less than 3 % of the amplitude of the corresponding fundamental frequency are insignificant and are disregarded. NOTE 1 A complex signal may consist of several fundamental frequencies (e.g. the pulse and the ripple current frequencies) and associated harmonics. For a simplified conservative assessment of induced current densities with non-sinusoidal or pulsed waveforms the procedure given in 5.4.4, based on the determination of an equivalent frequency, may be applied. NOTE 2 Further guidance may be found in the ICNIRP statement “Guidance on determining compliance of exposure to pulsed and complex non-sinusoidal waveforms below 100 kHz with ICNIRP guidelines” [3]. 5.4.2 Summation for basic restriction assessment 5.4.2.1 Summation of current density components without phase information For summation of induced current density Equation (6) may be applied.
∑==MHzHziiLitJJJ101, (6) where Jt
is the total relative induced current density, expressed as a fraction of the permissible value Ji
is the induced current density component at frequency ƒI; JL,i
is the corresponding current density limit at frequency ƒi; The sum of the weighted spectral components shall not exceed 1. As no phase information is used in this summation formula, this method can lead to significant overestimation of exposure. When information on the phase-angles of spectral components is available, the procedure given in 5.4.2.2 may be applied. 5.4.2.2 Summation of currents density components including phase information As the spectral components of a pulsed or non-sinusoidal signal are typically not in phase (i.e. they do not reach their maximum value at the same time in the time domain), Equation (6) provides a conservative approach to the assessment of exposure. Therefore Equation (7) may be used for a more realistic summation whenever the phases of the spectral components are available.



– 11 – EN 50444:2008 The sum of the weighted spectral components shall not exceed 1 at any time t within the evaluation interval, which shall be one period of the pulsed or non-sinusoidal signal. The time increments used for evaluation shall be less than or equal to 1/10 of the period of the highest relevant spectral component.
1)2cos(,≤++∑iiiiiLitfJJϕθπ (7) where Ji
is the induced current density spectral component at frequency ƒI; JL,i
is the corresponding current density limit at frequency ƒi, see Annex F; ƒi
is the frequency of the spectral component i (components up to 10 MHz maximum) ; θi
is the phase angle of the spectral component at frequency ƒI; ϕi
is the phase angle of the weighting function at frequency ƒi, see Annex F. 5.4.2.3 Summation of specific absorption rate (SAR) components Thermal effects due to EMF will be negligible for most types of arc welding equipment. If relevant spectral components (see 5.4.1) in the frequency range (see 5.6) above 100 kHz exist, Equation (8) shall be applied for summation of SAR spectral components.
∑==GHzkHziiLitSARSARSAR10100, (8) where SARt
is the total SAR, expressed as a fraction of the permissible value; SARi
is the SAR spectral component at frequency ƒI; SARL,i
is the corresponding SAR limit at frequency ƒi. 5.4.3 Summation for reference level assessment 5.4.3.1 Summation for stimulation effects without phase information For summation of magnetic field strength spectral components with respect to stimulation effects, Equation (9) may be applied.
∑∑+==MHzfifHziiLitscoscobHHHH101, (9) where Ht
is the total relative magnetic field strength, expressed as a fraction of the permissible value; ƒsco
is the summation cut off frequency in accordance with the reference document for the limit values;
Hi
is the magnetic field strength component at frequency ƒi; HL,i
is the corresponding magnetic field strength reference level at frequency ƒi; b
is the permissible magnetic field strength value defined in the reference document for the limit values.



EN 50444:2008 – 12 – For summation of magnetic flux density spectral components with respect to stimulation effects, Equation (10) may be applied
∑∑+==MHzfifHziiLitscoscobBBBB101, (10) where Bt
is the total relative magnetic flux density, expressed as a fraction of the permissible value; ƒsco
is the summation cut off frequency in accordance with the reference document for the limit values; Bi
is the magnetic flux density component at frequency ƒI; BL,i
is the corresponding magnetic flux density reference level at frequency ƒI; b
is the permissible magnetic flux density value defined in the reference document for the limit values. An example for a summation without phases is given in B.8. 5.4.3
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