EN 50505:2008

SLOVENSKI STANDARD
01-september-2008
Osnovni standard za oceno izpostavljenosti ljudi elektromagnetnim sevanjem
opreme za uporovno varjenje in sorodne procese
Basic standard for the evaluation of human exposure to electromagnetic fields from
equipment for resistance welding and allied processes
Grundnorm für die Bewertung der menschlichen Exposition gegenüber
elektromagnetischen Feldern von Einrichtungen zum Widerstandsschweißen und für
verwandte Verfahren
Norme de base destinée à l’évaluation de l’exposition humaine aux champs
électromagnétiques émanant du matériel de soudage par résistance et des techniques
connexes
Ta slovenski standard je istoveten z: EN 50505:2008
ICS:
13.280 Varstvo pred sevanjem Radiation protection
25.160.10 Varilni postopki in varjenje Welding processes
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN 50505
NORME EUROPÉENNE
April 2008
EUROPÄISCHE NORM
ICS 25.160.30
English version
Basic standard for the evaluation
of human exposure to electromagnetic fields
from equipment for resistance welding
and allied processes
Norme de base destinée à l’évaluation  Grundnorm für die Bewertung
de l’exposition humaine der menschlichen Exposition gegenüber
aux champs électromagnétiques émanant elektromagnetischen Feldern
du matériel de soudage par résistance von Einrichtungen zum Widerstands-
et des techniques connexes schweißen und für verwandte Verfahren

This European Standard was approved by CENELEC on 2008-03-01. 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.

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 50505:2008 E
Foreword
This European Standard was prepared by the Technical Committee CENELEC TC 26B, Electric
resistance welding.
The text of the draft was submitted to the formal vote and was approved by CENELEC as EN 50505
on 2008-03-01.
The following dates were fixed:

– latest date by which the EN has to be implemented

at national level by publication of an identical
(dop) 2009-03-01
national standard or by endorsement

– latest date by which the national standards conflicting
(dow) 2011-03-01
with the EN have to be withdrawn
This European Standard shall 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.
__________
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Contents
1 Scope . 5
2 Normative references . 6
3 Definitions . 6
3.1 General . 6
3.2 Specific for resistance welding and similar applications . 8
4 Physical quantities, units and constants .10
4.1 Quantities and units .10
4.2 Constants.10
5 Assessment procedures .10
5.1 General .10
5.2 Resistance welding equipment EMF emission description .10
5.3 Assessment conditions .11
5.4 Averaging.11
5.5 Pulsed or non-sinusoidal welding current .12
5.6 Conductivity of living tissue .18
5.7 Frequency range limitations .18
5.8 Application of assessment procedures .19
5.9 Measurements .21
5.10 Analytical calculations .23
5.11 Numerical calculations .28
6 Uncertainty of assessment .30
6.1 Including uncertainty .30
6.2 Evaluation of uncertainties .31
6.3 Reasonable overall uncertainties .31
6.4 Examples of typical uncertainties .32
7 Assessment report .32
7.1 General principles .32
7.2 Items to be recorded in the assessment report .33
Annex A (normative) Assessment parameters .34
Annex B (informative) Examples for exposure assessment .46
Annex C (informative) Numerical simulation using anatomical body models .59
Annex D (normative) Determination of coupling factor .63
Annex E (informative) Summation weighting and transfer function examples .65
Annex F (informative) Example for an uncertainty budget .70
Bibliography .71
Figures
Figure 1 – Example for parameters of a welding current sequence . 12
Figure 2 – Average electrical conductivities for homogeneous body modelling from 10 Hz to
10 MHz . 18
Figure 3 – Double parallel conductor model . 25
Figure 4 – Rectangular conductor model . 26
Figure A.1 – Points of investigation for stationary welding equipment . 35
Figure A.2 – Point of investigation for portable hand-held welding equipment . 36

Figure A.3 – Point of investigation for suspended welding equipment . 37
Figure A.4 – Point of investigation for a single side welding tool . 38
Figure A.5 – Point of investigation for a double side welding tool . 38
Figure A.6 – Simulation geometry for stationary equipment . 40
Figure A.7 – Simulation geometry A . 41
Figure A.8 – Simulation geometry B . 42
Figure A.9 – Simulation geometry C . 43
Figure A.10 – Simulation geometry for single side welding tool equipment . 44
Figure A.11 – 3D models dimensions for spheroid and cylindrical models . 45
Figure B.1 – Flux density waveform and r.m.s. spectral components for summation. 48
Figure B.2 – Summation of ratios B / B including phases in the time domain . 49
i L,i
Figure B.3 – Flux density waveform and r.m.s. spectral components for summation. 50
Figure B.4 – Current density distribution on disk diameter for f = 50 Hz. 51
Figure B.5 – Summation of ratios J / J including phases in the time domain . 52
i L,i
Figure B.6 – Welding current and measured field waveform . 53
Figure B.7 – Obtained flux density waveform and r.m.s. spectral components . 55
Figure B.8 – Summation of ratios J / J including phases in the time domain . 56
i L,i
Figure B.9 – J spectral components summation including phases in the time domain. 56
Figure B.10 – Measurement sensor position. 57
Figure E.1 – Peak reference level transfer function and tabulated values . 66
Figure E.2 – B summation weighting function and phase tabulated values . 67
Figure E.3 – Peak basic restriction transfer function and tabulated values . 68
Figure E.4 – J summation weighting function and phase tabulated values . 69
Tables
Table 1 – Permissible assessment procedures for resistance welding equipment . 19
Table 2 – Reasonable expanded assessment uncertainties . 31
Table B.1 – Flux density spectral components. 47
Table B.2 – Flux density spectral components. 48
Table B.3 – Flux density spectral components. 49
Table B.4 – Flux density spectral components. 50
Table B.5 – Result of flux density spectral components summation . 50
Table B.6 – Result of current density spectral components summation . 51
Table B.7 – Result of spectral components summation . 54
Table B.8 – Flux density and induced current spectral components . 55
Table C.1 – Electrical conductivity of tissue types . 61
Table F.1 – Example uncertainty budget for broadband field measurement . 70

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1 Scope
This European Standard applies to equipment for resistance welding and allied processes designed
for use in industrial or domestic environments.
NOTE 1 Typical allied processes are resistance hard and soft soldering or resistance heating achieved by means comparable
to resistance welding equipment.
This European Standard establishes a suitable evaluation method for determining the electromagnetic
fields in the space around the equipment and defines standardized operating conditions and
measuring distances. It provides a method to show conformity with guidelines or requirements
concerning human exposure to electromagnetic fields.
The Directive 2006/95/EC of the European Parliament and the Council [1], Article 2, stipulates that the
Member States take all appropriate measures to ensure that electrical equipment may be placed on
the market only if, having been constructed in accordance with good engineering practice in safety
matters in force in the Community, it does not endanger the safety of persons, domestic animals or
property when properly installed and maintained and used in applications for which is was made. The
principal elements of those safety objectives are listed in Annex I Clause 2.b. This standard may be
used in conjunction with EN 50445 for demonstration of conformity to the Council Directive with
reference to human exposure to electromagnetic fields (EMF). There are additional requirements
covered by Article 2 and Annex I Clause 2.b, which are not included in this document.
The Council Recommendation 1999/519/EC [2] provides Basic Restrictions and Derived reference
levels for exposure of the general public. This standard may be used for demonstration of resistance
welding equipment conformity to the Council Recommendation on this basis, but there may be
additional specific national or international requirements which are not included.
The ICNIRP Guidelines [3], on limits of exposure to static magnetic fields as well as for limiting
exposure in time varying electric, magnetic and electromagnetic fields, provide Basic restrictions and
Derived reference levels for both occupational and general exposure. This standard may be used for
demonstration of equipment conformity to ICNIRP Guidelines on this basis, but there may be
additional national or international requirements which are not included.
It is also possible to use this document as a basis to demonstrate conformity of resistance welding
equipment to other national and international guidelines or requirements with regard to human
exposure from EMF, for example Council Directive 2004/40/EC [4] on the minimum health and safety
requirements regarding the exposure of workers to the risk arising from physical agents
(electromagnetic fields), or the requirements of the Directive 98/37/EC [5]. In these cases, other
restrictions and levels than those referenced above may be used.
Other standards may apply to equipment 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.
The frequency range covered is 0 Hz to 300 GHz.
NOTE 2 Procedures to demonstrate conformity are not specified for the whole frequency range.

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 2004 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 2008 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 61566 1997 Measurement of exposure to radio-frequency electromagnetic
fields – Field strength in the frequency range 100 kHz to 1 GHz
(IEC 61566:1997)
EN 62226-1 2005 Exposure to electric or magnetic fields in the low and intermediate
frequency range – Methods for calculating the current density and
internal electric field induced in the human body – Part 1: General
(IEC 62226-1:2004)
EN 62226-2-1 2005 Exposure to electric or magnetic fields in the low and intermediate
frequency range – Methods for calculating the current density and
internal electric field induced in the human body – Part 2-1: Exposure
to magnetic fields – 2D models (IEC 62226-2-1:2004)
EN ISO/IEC 17025 2005 General requirements for the competence of testing and calibration
laboratories (ISO/IEC 17025:2005)
IEC 61786 1998 Measurement of low-frequency magnetic and electric fields with
regard to exposure of human beings – Special requirements for
instruments and guidance for measurements
ISO 669 2000 Resistance welding – Resistance welding equipment – Mechanical
and electrical requirements
3 Definitions
3.1 General
For the purposes of this document, the following terms and definitions apply.
3.1.1
averaging time (t )
avg
appropriate time over which exposure is averaged for purposes of determining conformity
3.1.2
basic restrictions
restrictions on exposure to electric, magnetic and electromagnetic fields that are based directly on
established health effects and biological considerations
3.1.3
compliance boundary
spatial border outside which any point of investigation is deemed to be compliant
3.1.4
conductivity (σ)
ratio of the conduction current density in a medium to the electric field strength

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3.1.5
contact current
current flowing into the body by touching a conductive object in an electromagnetic field
3.1.6
coupling factor (K)
used to enable exposure assessment for complex exposure situations, such as non-uniform magnetic
field or perturbed electric field
NOTE The coupling factor K has different physical interpretations depending on whether it relates to electric or magnetic field
exposure. The value of the coupling factor K depends on the model used for the field source and the model used for the human
body.
3.1.7
effective reference level (B )
L,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
3.1.8
EMF
electric, magnetic or electromagnetic field
3.1.9
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
3.1.10
exposure level
value of the quantity evaluated when a person is exposed to electromagnetic fields or contact currents
3.1.11
exposure, non-uniform
results when fields are non-uniform over volumes comparable to the whole human body
3.1.12
induced current density (J)
electromagnetic field induced current per unit area inside the body
3.1.13
magnetic field strength (H)
r
magnitude of a field vector in a point that results in a force ( F ) on a charge (q) moving with velocity
r
( v )
r r
F = q(v × µH )
(1)
or magnetic flux density divided by permeability of the medium
3.1.14
magnetic flux density (B)
magnitude of a field vector that is equal to the magnetic field strength (H) multiplied by the
permeability (µ) of the medium
B = µ H (2)
3.1.15
permeability (µ)
property of a material which defines the relationship between magnetic flux density (B) and magnetic
field strength (H)
NOTE 1 It is commonly used as the combination of the permeability of free space (µ ) and the relative permeability for
specific dielectric materials (µ ).
R
µ = µ µ (3)
R 0
-1
NOTE 2 Permeability is expressed in henry per metre (H m ).
3.1.16
point of investigation (POI)
location in space at which the value of the 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.
3.1.17
root-mean-square (r.m.s.)
effective value or the value associated with joule heating, of a periodic signal
NOTE The r.m.s. value is obtained by taking the square root of the mean of the squared value of a function.
T
x = x (t)dt
rms (expression in time domain) (4)
∫
T
where x(t) is the signal at time t, T is the signal period or multiples of it
x = x
(expression in frequency domain) (5)
rms ∑ n
n
th
where x is the magnitude of spectral component at n frequency, expressed as r.m.s. value.
n
3.1.18
reference levels
directly measurable quantities, derived from basic restrictions, provided for practical exposure
assessment purposes
NOTE Respect of the reference level will ensure respect of the relevant basic restriction. If the reference level is exceeded, it
does not necessarily follow that the basic restriction will be exceeded.
3.1.19
response time
time required for field strength indicated by a measurement instrument to reach 90 % of its final value
when the instrument is exposed to a defined step function of field strength
NOTE This step function is defined as a change in field strength from less than 1 % of the full scale deflection (fsd) of the
measurement instrument to 100 % of fsd occurring in a time of 1/4 of the period of the waveform at the frequency of interest.
3.2 Specific for resistance welding and similar applications
3.2.1
conventional load
load condition with the electrodes short-circuiting as defined in ISO 669:2000
3.2.2
current flow time
duration defined from the start time of current conduction to the time when its current has decreased to
10 % level of the measured welding current value
3.2.3
duty factor (X)
ratio for a given interval of the on-load duration to the total time
NOTE This ratio, lying between 0 and 1, may be expressed as a percentage.

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3.2.4
equipment for resistance welding and allied processes
equipment associated with carrying out the processes of resistance welding or allied processes
consisting of e.g. power source, electrodes, tooling and associated control equipment, which may be a
separate unit or part of a complex machine
3.2.5
hand-held integrated transformer gun
resistance welding equipment with built-in transformer and all conductors carrying their welding
current, which is intended to be held in the hand during use
3.2.6
hand-held separated transformer gun
resistance welding equipment with separate transformer, which is intended to be held in the hand
during use
3.2.7
maximum short-circuit current output (I )
2cc
equipment rated output current with conventional load as defined in ISO 669:2000, Clause 10
3.2.8
phase control
typical current control technique in resistance welding, e.g. by changing the firing angle in each
half-weld cycle of a.c. current
3.2.9
processes allied to resistance welding
processes which are carried out on machines comparable to resistance welding equipment
NOTE Typical allied processes are resistance hard and soft soldering or resistance heating achieved by means comparable to
resistance welding equipment.
3.2.10
stationary resistance welding equipment
resistance welding equipment which is stationary, the operator handle the piece to be welded
3.2.11
suspended integrated transformer gun
resistance welding equipment with built-in transformer and all conductors carrying their welding
current, which is intended to be suspended and hand-guided by the operator to position the equipment
in the correct welding position
3.2.12
suspended separated transformer gun
resistance welding equipment with separate transformer, which is intended to be suspended and
hand-guided by the operator to position the equipment in the correct welding position
3.2.13
weld time
current flow time given as a number of cycles of the mains frequency or as time duration
3.2.14
welding cable(s)
flexible conductor(s) used to connect the power source and the welding tool in some types of
resistance welding equipment
NOTE Typical examples of these equipments are the car-body production and repair welding-station.

3.2.15
welding circuit
circuit that includes all conductive material through which the welding current is intended to flow
3.2.16
welding current
current value accumulated over the weld time and indicated by the r.m.s. value, which is applicable for
a.c. and d.c. current
NOTE In the case of pulsed current, e.g. a capacitor discharged current, the welding current is indicated by the peak value.
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
-2
Current density J Ampere per square metre A m
-1
Electric conductivity σ Siemens per metre S m
Frequency f Hertz Hz
-1
Magnetic field strength H Ampere per metre A m
-2
Magnetic flux density B Tesla T (Vs m )
-1
Permeability µ Henry per metre H m

4.2 Constants
Physical constant Symbol Magnitude
-7 -1
Permeability of free space
µ 4π × 10 H m
5 Assessment procedures
5.1 General
This European Standard defines, as far as possible, suitable points of investigation for different types
of equipment that represent the highest exposure positions during practical use. These points of
investigation are based on previous experience and measurement, taking into account typical operator
positions, and have been selected to protect against effects on central nervous system tissues in the
head and trunk of the body.
NOTE 1 Equipment complying with the basic restriction or reference levels at the points of investigation defined in this
European Standard are considered to be compliant with the requirements of the reference document that contains limits.
NOTE 2 Equipment that does not comply with these tests needs to be carefully evaluated to quantify the exposure in all
relevant operator positions. This evaluation shall define compliance boundaries that describe all the operator positions that are
in conformity with the requirements. The equipment use shall be restricted according to the established compliance boundaries.
5.2 Resistance welding equipment EMF emission description
The main source of EMF in a resistance welding equipment is the welding current flowing through the
welding circuit, generating a low frequency magnetic field, this has the greatest influence on the
exposure level.
The emission is a non homogeneous field at the proximity of equipment.

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The parameters of the welding current (e.g. amplitude and waveform), and the welding circuit
characteristics (e.g. dimensions), are determined by the equipment only. External factors e.g.
characteristics of the workpiece have influence on the magnetic field, but are not taken into account by
this standard.
The emission is present only during welding process, therefore only assessment in operator position
during welding is required, no assessment is required in positions used for equipment programming or
set-up.
Therefore assessment shall be based on these parameters and the configuration of the welding circuit
as specified in this standard.
NOTE The fact that magnetic field in the surrounding space of a resistance welding equipment is non-homogeneous shall be
taken into account.
5.3 Assessment conditions
Test configurations, points of investigation, operating conditions and other parameters, which are valid
for all evaluation procedures, are specified in Annex A.
5.4 Averaging
5.4.1 General
Time and spatial averaging shall be made in accordance with the relevant document containing limits.
Specific criteria for resistance welding equipment given in 5.4.2 and 5.4.3 shall be used if no or less
detailed averaging procedures are provided by the document containing the limits.
5.4.2 Time averaging
For occupational exposure the d.c. component of the magnetic flux density or field strength values
should be averaged over a time interval of 8 h, taking into account the duty cycle of the equipment and
the welding current output sequence, as applicable. The reduction factor shall be calculated:
– for constant d.c. current as
X
Vrdc =
(6)
where
X is the duty cycle of the welding equipment, expressed in %, calculated by
I
2p
X = ⋅100
(7)
I
2cc
– for welding current output sequences as
n
X 1
Vrdcs = In ⋅ tn
(8)
∑
100 t
cs
i=1
where
X is the duty cycle of the welding equipment, expressed in %;
t is the sequence cycle time;
cs
Ι is the d.c. level during time interval n;
n
t is the duration of interval n.
n
t
3 t4
I
t
I
I
2 4
t
I
t
cs
0 2 4 8 10 12
t [min]
Figure 1 – Example for parameters of a welding current sequence
For general public exposure of d.c. component or exposure to time varying magnetic fields, time
averaging shall be performed according the relevant document containing limits.
5.4.3 Spatial averaging of magnetic field
Generally reference levels are intended to be spatially averaged values over the entire body of the
exposed individual, but with the important proviso that the basic restrictions on localized exposure are
not exceeded.
This European Standard is used to assess mainly the exposure generated from the welding circuit,
creating stimulation effects. The maximum exposure is localized on the part of the body nearest to the
source. In this type of situation an approach based on the spatial averaging of non uniform field
distributions underestimates the exposure and is not able to ensure that the localized exposure does
not exceed the basic restrictions for induced current densities. Therefore spatial averaging shall not be
applied to reference level based exposure assessment of stimulation effects due to fields generated
from welding circuit.
For evaluation of exposure generated from sources other than the welding circuit (for example from
microprocessors, radio communication systems, ancillary equipment) spatial averaging of the field
may be appropriate.
5.5 Pulsed or non-sinusoidal welding current
5.5.1 General
Welding current of resistance welding equipment are typically pulsed current, therefore the generated
magnetic field is of pulsed type. Some type of resistance welding equipment (i.e. seam welders)
generates sustained field. The waveform of the welding current depends from the welding technology
used by the equipment.
For pulsed or non-sinusoidal (including a d.c. component) welding current a separate evaluation 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.
Different frequency ranges of the signal (e.g. due to rise and fall time of welding pulse or welding
current ripple) may be evaluated separately. In this case the results of each evaluation shall be added
linearly. Care must be taken to ensure that no applicable frequency band is disregarded, and that
overlapping frequency ranges do not lead to an overestimation of exposure.
The a.c. component may consist of a number of spectral components, typically a fundamental
frequency (e.g. the mains frequency or, ripple frequency for rectifiers) and harmonics.
It is important to determine whether, in situations of simultaneous exposure to fields of different
frequencies, these exposures are additive in their effects. Additivity is generally applicable to thermal
effects and should be examined separately for electrical stimulation.
I [kA]
- 13 - EN 50505:2008
These spectral components shall be summed for assessment of exposure, summation shall take into
account 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 5.5.2 and 5.5.2.4.
Only spectral components up to the upper frequency defined in 5.7 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 5.5.3, 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” [6].
5.5.2 Summation for basic restriction assessment
5.5.2.1 Summation of currents density components without phase information
For summation of induced current density Equation (9) may be applied.
10 MHz
J
i
J =
(9)
t
∑
J
L,i
i=1 Hz
where
J is the total relative induced current-density, expressed as a fraction of the permissible
t
value;
J is the induced current-density component at frequency f;
i i
J is the corresponding current-density limit at frequency f .
L,i i
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 5.5.2.2 may be applied.
5.5.2.2 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 (9) provides a
conservative approach to the assessment of the exposure. Therefore Equation (10) may be used for a
more realistic summation whenever the phases of the spectral components are available.

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 smaller or equal than 1/10 of the period of the highest relevant spectral
component.
J
i
cos(2πf t + θ + ϕ ) ≤ 1
i i i (10)
∑
J
L,i
i
where
J is the induced current-density spectral component at frequency f ;
i i
J is the corresponding current-density limit at frequency f;
L,i i
f is the frequency of the spectral component i (components up to 10 MHz maximum);
i
θ is the phase angle of the spectral component at frequency f;
i i
ϕ is the phase angle of the weighting function at frequency f as defined in the reference
i i
document for the limit values.
Alternatively summation may be performed using a weighting function having a magnitude equal to the
inverse of the peak basic restriction. The weighting function phase is based on the cut off frequency
specified in the reference document. The weighting function shall be established using first order
filters.
(WF) A cos(2πf t + θ + ϕ ) ≤ 1
i i i i i (11)
∑
i
where
A is the amplitude of the spectral component at frequency f (peak value);
i i
(WF) is the amplitude of the weighting function at frequency f
i i;
f is the frequency of the spectral component i (components up to 10 MHz maximum);
i
θ is the phase angle of the spectral component at frequency f;
i i
ϕ is the phase angle of the weighting function at frequency f.
i i
NOTE An example for such a weighting function is given in Annex E. 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” [6], EN 50392 and EN 50366 [7].
Examples for summation including phase information are given in B.2.7 and B.3.4.
5.5.2.3 Summation of specific absorption rate (SAR) components
Thermal effects due to EMF will be negligible for most types of resistance welding equipment. If
relevant spectral components (see 5.5.1) in the frequency range (see 5.7) above 100 kHz exist,
Equation (12) shall be applied for summation of SAR spectral components.
10 GHz
SAR
i
SAR =
(12)
t ∑
SAR
L,i
i=100 kHz
where
SAR is the total SAR, expressed as a fraction of the permissible value;
t
SAR is the SAR spectral component at frequency f ;
i i
SAR is the corresponding SAR limit at frequency f.
L,i i
- 15 - EN 50505:2008
5.5.2.4 Summation for reference level assessment
5.5.2.5 Summation for stimulation effects without phase information
For summation of magnetic field strength spectral components with respect to stimulation effects,
Equation (13) may be applied.
f
10 MHz
sco
H H
i i
H = +
(13)
t
∑ ∑
H b
L,i
i=1 Hz f
sco
where
H is the total relative magnetic field strength, expressed as a fraction of the permissible
t
value;
f is the summation cut off frequency in accordance with the reference document for
sco
the limit values;
H is the magnetic field strength component at frequency f ;
i i
H is the corresponding magnetic field strength reference level at frequency f;
L,i i
b is the permissible magnetic field strength value defined in the reference document for
the limit values.
For summation of magnetic flux density spectral components with respect to stimulation effects,
Equation (14) may be applied.
f 10 MHz
sco
B B
i i
B = +
(14)
t ∑ ∑
B b
L,i
i=1 Hz f
sco
where
B is the total relative magnetic flux density, expressed as a fraction of the permissible
t
value;
f is the summation cut off frequency in accordance with the reference document for
sco
the limit values;
B is the magnetic flux density component at frequency f;
i i
B is the corresponding magnetic flux density reference level at frequency f;
L,i i
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.2.3.
5.5.2.6 Effective reference level method
The assessment is performed by measuring the total r.m.s. magnetic flux density value using a
broadband probe. For evaluation of exposure the result of the broadband measurement is compared
to the calculated effective reference level B .
L,eff
The spectral content of the field shall be derived, e.g. by Fast Fourier Transformation (FFT) of the
measured field or, alternatively in case of field measurements around welding circuit, the measured
welding current. The contribution of each spectral component is calculated as a fraction of the total
a.c. r.m.s. flux density or welding current value.
The r.m.s. effective reference level is obtained using Equation (15).
B =
(15)
L,eff
F
i
∑
B
L,i
i
where
B is the corresponding r.m.s. magnetic flux density reference level at frequency f;
L,I i
F is the fractional contribution of the spectral component i, defined as
i
B
rms,i
F =
(16)
i
B
rms
where
B is the total r.m.s. magnetic flux density value;
r.m.s.
B is the r.m.s. value of the spectral component i
r.m.s.,I
or
I
rms,i
F =
(17)
i
I
rms
where
I is the total r.m.s. welding current value;
r.m.s.
I is the r.m.s. value of the spectral component i.
r.m.s.,i
NOTE 1 Further guidance may be found in the NRPB document W24 “Occupational Exposure to Electric and Magnetic Fields
in the Context of the ICNIRP Guidelines” [8].
NOTE 2 This method is helpful if numerous measurements of a field originating from the same source, and therefore with the
same waveform, shall be made using a broadband probe. The spectral contents have to be evaluated once only, the derived
effective reference level can be used for all measurements.
An example using this method is given in B.2.2.
5.5.2.7 Summation for stimulation effects 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), the procedure in accordance
with 5.5.2.5 provides a conservative approach to the assessment of the exposure. Therefore
Equation (18) may be used for a more realistic summation whenever the phases of the spectral
components are available. Equation (18) may be used for evaluation of B or H values.
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 smaller or equal than 1/10 of the period of the highest relevant spectral
component.
A
i
cos(2πf t + θ + ϕ ) ≤ 1
(18)
∑ i i i
L
i
i
where
A is the amplitude of the spectral component at frequency f;
i i
L is the applicable limit at frequency f, or, above f the value b as given in the
i i sco
reference document for the limit values;
f is the frequency of the spectral component i (components up to 10 MHz maximum);
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