IEC 60974-4:2010

IEC 60974-4
®
Edition 2.0 2010-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE


Arc welding equipment –
Part 4: Periodic inspection and testing

Matériel de soudage à l’arc –
Partie 4: Inspection et essais périodiques

IEC 60974-4:2010

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IEC 60974-4
®
Edition 2.0 2010-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE


Arc welding equipment –
Part 4: Periodic inspection and testing

Matériel de soudage à l’arc –
Partie 4: Inspection et essais périodiques

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
P
CODE PRIX
ICS 25.160 ISBN 978-2-88912-158-8
® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale

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– 2 – 60974-4 © IEC:2010
CONTENTS
FOREWORD.3
1 Scope.5
2 Normative references .5
3 Terms and definitions .5
4 General requirements .6
4.1 Qualification of test personnel .6
4.2 Test conditions.6
4.3 Measuring instruments .6
4.4 Periodic inspection and test.7
4.5 Maintenance.7
4.6 Repair .7
4.7 Test sequence.7
5 Protection against electrical shock.8
5.1 Visual inspection .8
5.2 Continuity of the protective circuit.8
5.3 Insulation resistance .8
5.4 Welding circuit leakage current.8
5.5 Primary leakage current .9
5.6 No-load voltage (U ) .11
0
6 Functional test.11
6.1 Function .11
6.2 Supply-circuit on/off switching device .12
6.3 Voltage-reducing device .12
6.4 Magnetic gas valve.12
6.5 Signal and control lamps .12
7 Documentation .12
7.1 Test report .12
7.2 Labelling .13
Annex A (informative) Check-list for the visual inspection .14
Annex B (informative) Example of a test report after repair .15
Annex C (informative) Equipment not built in accordance with IEC 60974-1.16

Figure 1 – Measurement of leakage current of welding circuit .9
Figure 2 – Measuring network for primary leakage current .10
Figure 3 – Principles of primary leakage current measurement for single phase
equipment.10
Figure 4 – Measurement of peak values.11

Table 1 – Test sequence on used arc welding equipment .7
Table 2 – Insulation resistance .8

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60974-4 © IEC:2010 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

ARC WELDING EQUIPMENT –

Part 4: Periodic inspection and testing


FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60974-4 has been prepared by IEC technical committee 26:
Electric welding.
This second edition cancels and replaces the first edition published in 2006. It constitutes a
technical revision.
The main significant technical changes with respect to the previous edition are the following:
– title is amended;
– scope is extended to equipment designed in accordance with IEC 60974-6;
– complementary instructions from the manufacturer shall be followed;
– qualification of test personnel is clarified (see 4.1);
– plasma cutting power sources are excluded from no-load voltage test (see 5.6);
– voltage reducing device functional test is simplified (see 6.3);
– supply voltage is recorded in test report (see 7.1).

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– 4 – 60974-4 © IEC:2010
The text of this standard is based on the following documents:
FDIS Report on voting
26/422/FDIS 26/428/RVD

Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
The list of all the parts of the IEC 60974 series, under the general title Arc welding equipment,
can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.

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60974-4 © IEC:2010 – 5 –
ARC WELDING EQUIPMENT –

Part 4: Periodic inspection and testing



1 Scope
This part of IEC 60974 specifies test procedures for periodic inspection and, after repair, to
ensure electrical safety. These test procedures are also applicable for maintenance.
This standard is applicable to power sources for arc welding and allied processes designed in
accordance with IEC 60974-1 or IEC 60974-6. Stand-alone ancillary equipment designed in
accordance with other part of IEC 60974 may be tested in accordance with relevant
requirement of this part of IEC 60974.
NOTE 1 The welding power source may be tested with any ancillary equipment fitted that could affect the test
results.
This standard is not applicable to testing of new power sources or engine-driven power
sources.
NOTE 2 For a power source not built in accordance with IEC 60974-1, see Annex C.
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.
IEC 60050-151, International Electrotechnical Vocabulary (IEV) – Part 151: Electrical and
magnetic devices
IEC 60050-195, International Electrotechnical Vocabulary (IEV) – Part 195: Earthing and
protection against electric shock
IEC 60050-851, International Electrotechnical Vocabulary (IEV) – Part 851: Electric welding
IEC 60974-1:2005, Arc welding equipment – Part 1: Welding power sources
IEC 60974-6, Arc welding equipment – Part 6: Limited duty manual metal arc welding power
sources
IEC 61557-4, Electrical safety in low voltage distribution systems up to 1 000 V a.c. and
1 500 V d.c. – Equipment for testing, measuring or monitoring of protective measures –
Part 4: Resistance of earth connection and equipotential bonding
3 Terms and definitions
For the purposes of this document, the terms and definitions given in the IEC 60050-151, the
IEC 60050-195, the IEC 60050-851, the IEC 60974-1, as well as the following, apply.

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– 6 – 60974-4 © IEC:2010
3.1
expert
competent person
skilled person
a 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.
[IEC 60974-1:2005, 3.3]
3.2
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
[IEC 60974-1:2005, 3.4]
3.3
periodic inspection and test
examination carried out at specified intervals to reduce the risk of hazard
3.4
maintenance
service carried out at specified intervals to reduce the risk of hazard and failure
3.5
repair
restore to a safe and intended operating condition
3.6
test personnel
instructed person or expert that has been trained and authorized to perform periodic
inspection and testing
4 General requirements
4.1 Qualification of test personnel
Tests of welding equipment can be hazardous and shall be carried out by an instructed
person or expert in the field of electrical repair, preferably also familiar with welding, cutting
and allied processes. Instructed persons should be considered qualified for simple periodic
testing and maintenance provided the equipment enclosure does not have to be opened.
NOTE Hazardous voltages and currents inside the equipment enclosure may cause shock, burn or death. Only
expert test personnel may open the equipment.
4.2 Test conditions
Tests shall be carried out at an ambient air temperature between 10 °C and 40 °C on dry and
cleaned welding equipment.
4.3 Measuring instruments
The accuracy of measuring instruments shall be class 2.5 as a minimum, except for the
measurement of insulation resistance, where the accuracy of the instruments is not specified
but shall be taken into account for the measurement.

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60974-4 © IEC:2010 – 7 –
4.4 Periodic inspection and test
The periodic inspection and test specified in Table 1 shall be carried out.
Tests shall be documented in a test report in accordance with 7.1.
During the tests, complementary instructions from the manufacturer shall be followed.
4.5 Maintenance
The manufacturer’s maintenance schedule and instructions shall be followed.
Tests shall be documented in a test report in accordance with 7.1.
4.6 Repair
After repair or replacement of a component which restores a welding or cutting function, an
expert shall select appropriate tests to be carried out, as specified in Table 1.
NOTE After a minor repair such as replacement of a lamp, wheel or under carriage, the tests given in Table 1 may
not be necessary.
Tests shall be documented in a test report in accordance with 7.1.
During the tests, complementary instructions from the manufacturer shall be observed (for
example, circuit diagrams, spare part list, functional test of power source and ancillary
equipment, etc.).
4.7 Test sequence
The test sequence is given in Table 1.
Table 1 – Test sequence on used arc welding equipment
Periodic inspection and test After repair
a) Visual inspection in accordance with 5.1 a) Visual inspection in accordance with 5.1
b) Electrical test: b) Electrical test:
– protective conductor resistance in accordance with – protective conductor resistance in accordance
5.2 with 5.2
a a
– insulation resistance in accordance with 5.3 – insulation resistance in accordance with 5.3
– no-load voltage in accordance with 5.6 – no-load voltage in accordance with 5.6

c) Functional test: c) Functional test:
– no requirement – function in accordance with 6.1
– supply-circuit on/off switching device in
accordance with 6.2
– voltage-reducing device in accordance with 6.3
– magnetic gas valve in accordance with 6.4
– signal and control lamps in accordance with 6.5
d) Documentation in accordance with Clause 7 d) Documentation in accordance with Clause 7
a
If the insulation resistance test cannot be carried out without disconnection of any component of the equipment to
be tested (e.g. interference suppression networks, protection capacitors or surge protection component), the
insulation resistance test may be replaced by both the primary and welding circuit leakage current tests in
accordance with 5.4 and 5.5.

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5 Protection against electrical shock
5.1 Visual inspection
Visual inspection shall be carried out in accordance with the conditions of use of welding
equipment and the manufacturer’s instructions.
An example of items for a visual inspection is given in Annex A.
5.2 Continuity of the protective circuit
For mains-powered welding equipment of protection class I, including ancillary equipment (for
example, cooling system) having mains connecting cables up to a length of 5,0 m, the
maximum measured protective conductor resistance shall not exceed 0,3 Ω.
For cables longer than 5,0 m, the permissible value of the protective conductor resistance is
increased by 0,1 Ω per additional 7,5 m cable. The maximum permissible value of the
protective conductor resistance is 1 Ω.
Conformity shall be checked by measuring the resistance between the protective conductor
contact at the plug and exposed conductive parts with testing equipment according to
IEC 61557-4.
During the measurement, the cables shall be bent, flexed or twisted along the whole length,
especially in the vicinity of cable entries into the enclosure, in order to detect interruptions in
the protective conductor.
5.3 Insulation resistance
The insulation resistance shall be not less than the values given in Table 2.
Table 2 – Insulation resistance
a
Measurement Resistance Insulation
Double or
Supply circuit to welding circuit 5,0 MΩ
reinforced
Welding circuit to protective circuit 2,5 MΩ Basic
Supply circuit to protective circuit 2,5 MΩ Basic
Supply circuit Double or
b
to accessible surfaces 5,0 MΩ
of Class II equipment reinforced
a Control circuits are tested together with the circuit to which they are galvanically connected.
b For measurement to accessible non-conductive surfaces, such surfaces shall be considered to be
covered by metal foil.

Conformity shall be checked by the stabilized measurement of the insulation resistance by
application of a d.c. voltage of 500 V at room temperature.
During the measurement, torches shall be disconnected, solid-state electronic components
and their protective devices may be short-circuited and liquid cooling units shall be tested
without liquid.
5.4 Welding circuit leakage current
The leakage current between the welding outlets and the protective conductor terminal shall
not exceed 10 mA a.c. r.m.s.

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60974-4 © IEC:2010 – 9 –
Conformity shall be checked by measurement of the leakage current with a circuit as shown in
Figure 1 at the rated supply voltage and no-load condition.
The measuring circuit shall have a total resistance of 1 750 Ω ± 250 Ω and be shunted by a
capacitor so that the time constant of the circuit will be 225 μs ± 15 μs.
In the case of 1 750 Ω, the capacitor will be 130 nF.

130 nF
mA
1 750 Ω
IEC  1904/06

NOTE For class II equipment, use the PE-terminal of earthed supply circuit network.
Figure 1 – Measurement of leakage current of welding circuit
5.5 Primary leakage current
The primary leakage current in the external protective conductor shall not exceed
a) 5 mA r.m.s. for plug-connected equipment rated up to and including 32 A;
b) 10 mA r.m.s. for plug-connected equipment rated more than 32 A;
c) 10 mA r.m.s. for equipment for permanent connection, without special measures for the
protective conductor;
d) 5 % of the rated input current per phase, for equipment for permanent connection with a
reinforced protective conductor.
Conformity shall be checked using the measuring circuit shown in Figure 2 with a
conventional voltmeter under the following conditions:
• the welding equipment is
– isolated from the ground plane;
– supplied by the rated supply voltage;
– not connected to the protective earth except through measurement
components;
• the output circuit is in the no-load condition;
• interference suppression capacitors shall not be disconnected.
NOTE 1 The circuit given in Figure 2 is used to obtain reproducible results.

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R C
S S
A
R
1
B
R U C U
B 1 2
1
IEC  1905/06


Key
A, B test terminals U rated supply voltage
1
R 1 500 Ω R 10 000 Ω
S 1
R U conventional load voltage
500 Ω
B 2
C C
0,22 μF 0,022 μF
S 1
U
2
Leakage current I =
PE
R
B
Figure 2 – Measuring network for primary leakage current
The measurement of the primary leakage current may be made direct or in the form of a
difference current measurement (see Figure 3). Instead of the ammeter shown in Figure 3, the
measuring circuit in Figure 2 shall be used. The tolerance of the component values in the
measurement circuit shall not exceed ±5 %.
Equipment for permanent connection with a reinforced protective conductor shall be tested
according to the manufacturer’s specification.

PE N/L L
PE N/L L
Measuring
Measuring
instrument
instrument
A
A
A
A
I I I
PE Out In I I I
Out In Dif.
B
B
Power
Power
source
source
IEC  1906/06
IEC  1907/06

Principle of direct measurement Principle of measurement according to the
difference current procedure
Figure 3 – Principles of primary leakage current measurement
for single phase equipment
NOTE 2 Caution! A qualified person should perform this test. The protective conductor is disabled for this test.

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60974-4 © IEC:2010 – 11 –
5.6 No-load voltage (U )
0
The peak values of the maximum no-load voltage at all possible settings of the power source
shall not exceed the values given in Table 13 of IEC 60974-1 when the power source is
supplied at rated supply voltage and frequency.
Before testing, arc striking and stabilizing devices shall, if necessary, be removed or by-
passed according to the manufacturer’s instructions (see also instructions for use or
manufacturer’s testing instructions).
The no-load voltage is measured between welding output terminals. If this is not possible for
safety or control reasons, the no-load voltage is measured between torch and welding return
cable connection. This test is not required for plasma cutting power sources.
If rated reduced no-load voltage (U ) or rated switched no-load voltage (U ) are defined on
R S
the rating plate, U or U shall be measured instead of U .
R S 0
Conformity shall be checked by measurement of
a) r.m.s. values
A true r.m.s. meter is used with a resistance of the external welding circuit of 5 kΩ.
b) peak values
To obtain reproducible measurements of peak values, omitting impulses which are not
dangerous, a circuit is used as shown in Figure 4.

1
1 kΩ
0,2 kΩ
U
0 10 nF
6,8 μF V
0-5 kΩ
1 = Diode 1N4007 or similar
IEC  1908/06

Figure 4 – Measurement of peak values
The voltmeter shall indicate mean values. The measurement range chosen shall be as near
as possible to the actual value of the no-load voltage. The voltmeter shall have an internal
resistance of at least 1 MΩ.
The tolerance of the component values in the measurement circuit shall not exceed ±5 %. The
minimum power for the resistor of 0,2 kΩ is 65 W. The rheostat shall withstand a current value
of 0,6 A. The capacitor shall have a minimum voltage rating of 200 V.
6 Functional test
6.1 Function
Each safety-related function judged as relevant by the test personnel shall be checked for
correct operation.

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– 12 – 60974-4 © IEC:2010
Conformity shall be checked by operating the device and by checking whether the welding
power source operates correctly.
6.2 Supply-circuit on/off switching device
Where an integral supply-circuit on/off switching device (for example, switch, contactor or
circuit-breaker) is fitted, this shall:
a) open or close all ungrounded mains conductors;
b) clearly indicate whether the circuit is open or closed.
Conformity shall be checked by visual inspection and measurement.
6.3 Voltage-reducing device
Where a voltage-reducing device is f
...