SIST EN ISO 5826:2014

Resistance welding equipment - Transformers - General specifications applicable to all transformers (ISO 5826:2014)

ISO 5826:2014 gives specifications applicable to transformers of IEC 61140 protection class I or II of the following types for use in resistance welding equipment: single-phase transformers for a.c. welding, typically operating at 50 Hz or 60 Hz; single-phase transformers with connected rectifier for d.c. welding, typically operating at 50 Hz or 60 Hz; single-phase inverter transformers with connected rectifier for d.c. welding, typically operating at 400 Hz to 2 kHz; three-phase transformers with connected rectifier for d.c. welding, typically operating at 50 Hz or 60 Hz.

Widerstandsschweißeinrichtungen - Transformatoren - Allgemeine Anforderungen anwendbar für alle Transformatoren (ISO 5826:2014)

Diese Internationale Norm enthält Spezifikationen, die für die folgenden Arten von Transformatoren zum Gebrauch in Widerstandsschweißeinrichtungen anwendbar sind:
- einphasige Transformatoren mit Schweiß-Wechselstrom, üblicherweise bei 50 Hz oder 60 Hz betrieben;
- einphasige Transformatoren mit angeschlossenem Gleichrichter für Schweiß-Gleichstrom, üblicherweise bei 50 Hz oder 60 Hz betrieben;
- einphasiger Inverter-Transformator mit angeschlossenem Gleichrichter für Schweiß-Gleichstrom, üblicherweise bei 400 Hz bis 2 kHz betrieben;
- dreiphasige Transformatoren mit angeschlossenem Gleichrichter für Schweiß-Gleichstrom, üblicherweise bei 50 Hz oder 60 Hz betrieben;
Für die Anwendung dieser Internationalen Norm kann sich der Begriff Transformator auf einen einzelnen Transformator oder auf einen Transformator zusammen mit einem Gleichrichter (Transform-atoren-Gleichrichtereinheit) beziehen.
Diese Internationale Norm gilt für Transformatoren, die nach Schutzklasse I oder II entsprechend IEC 61140 gebaut wurden.
ANMERKUNG Die Anforderungen dieser Internationalen Norm können durch andere Normen für Widerstands-schweißtransformatoren ersetzt werden, z. B. ISO 22829 und ISO 10656.

Matériel de soudage par résistance - Transformateurs - Spécifications générales applicables à tous les transformateurs (ISO 5826:2014)

ISO 5826:2014 donne les spécifications applicables aux types de transformateur suivants utilisés pour le matériel de soudage par résistance avec ou sans redresseur: transformateurs monophasés pour courant alternatif de soudage, fonctionnant généralement à 50 Hz ou 60 Hz; transformateurs monophasés avec redresseur pour courant continu de soudage fonctionnant généralement à 50 Hz ou 60 Hz; transformateurs à onduleur monophasés avec redresseur pour courant continu de soudage fonctionnant généralement de 400 Hz à 2 kHz; transformateurs triphasés avec redresseur pour courant continu de soudage fonctionnant généralement à 50 Hz ou 60 Hz.

Oprema za uporovno varjenje - Transformatorji - Splošne specifikacije, veljavne za vse transformatorje (ISO 5826:2014)

Standard EN-ISO 5826 določa specifikacije, ki se uporabljajo za vse transformatorje za opremo za uporovno varjenje s priključenim usmernikom ali brez. Vključene so naslednje vrste: – enofazni transformatorji za izmenični varilni tok, ki običajno obratujejo pri frekvenci 50 ali 60 Hz; – enofazni transformatorji s priključenim usmernikom, ki običajno obratujejo pri frekvenci 50 ali 60 Hz; – enofazni inverterski varilni transformator s priključenim usmernikom, ki običajno obratuje pri frekvenci 400 Hz do 2 kHz; – trifazni transformatorji s priključenim usmernikom, ki običajno obratujejo pri frekvenci 50 ali 60 Hz. Za namene tega mednarodnega standarda izraz transformator označuje samo transformator ali transformator v kombinaciji z drugimi komponentami, kot je zgoraj omenjeni usmernik. Ta mednarodni standard se v skladu s standardom IEC 61140 uporablja za vse transformatorje zaščitnega razreda I ali II.

General Information

• Status: Published
• Public Enquiry End Date: 31-Dec-2013
• Publication Date: 30-Mar-2014
• ICS: 25.160.30 - Welding equipment
• ICS: 29.180 - Transformers. Reactors
• Technical Committee: VAR - Welding
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 14-Mar-2014
• Due Date: 19-May-2014
• Completion Date: 31-Mar-2014
• Ref Project: EN ISO 5826:2014 - Resistance welding equipment - Transformers - General specifications applicable to all transformers (ISO 5826:2014)

Relations

• Replaces: SIST EN ISO 5826:2003 - Resistance welding equipment - Transformers - General specifications applicable to all transformers (ISO 5826:1999)
• Effective Date: 01-May-2014

Overview

EN ISO 5826:2014 - "Resistance welding equipment - Transformers - General specifications applicable to all transformers" is the CEN-endorsed version of ISO 5826:2014. It specifies general requirements for transformers used in resistance welding equipment (the transformer alone or as a transformer‑rectifier unit). The standard covers transformers of IEC 61140 protection class I or II and applies to a range of transformer types and operating frequencies used in resistance welding.

What the standard covers

• Transformer types: single‑phase for a.c. welding (typically 50/60 Hz); single‑phase with rectifier for d.c. welding (50/60 Hz); single‑phase inverter transformers with rectifier for d.c. welding (400 Hz to 2 kHz); and three‑phase transformers with rectifier for d.c. welding (50/60 Hz).
• General construction and additional equipment such as thermal protection and output current sensing coils.
• Physical environment and operating conditions, including ambient temperature, humidity, altitude, handling, transportation and cooling liquid temperature.
• Testing requirements: type tests and routine tests with defined test conditions.
• Electrical safety: insulation resistance, dielectric strength, calibration of sensing coils, and protection against electric shock in normal and fault conditions.
• Thermal rating: temperature rise limits, heating test conditions and measurement methods.
• Performance parameters: rated output voltage (a.c. and d.c. no‑load), no‑load input current, short‑circuit voltage and output current under load.
• Cooling liquid circuit, dynamic behaviour, rating plate content and required instruction manual information.
• Annexes include example rating plates, altitude/cooling corrections, concept notes and a type code example.

Key technical topics and requirements

• Safety and insulation: requirements to protect against direct and indirect contact, including insulation resistance and dielectric strength tests.
• Thermal management: mandatory thermal protection and temperature‑rise testing to define permissible operating limits.
• Performance testing: type and routine test procedures for verifying rated output, short‑circuit voltage and no‑load currents.
• Documentation: mandatory rating plate fields and comprehensive instruction manual content for safe installation and operation.

Applications and users

• Applies to manufacturers, designers and test laboratories of resistance welding transformers and transformer‑rectifier units.
• Useful to OEMs of welding machines, quality assurance and compliance teams, safety engineers, and procurement specialists specifying welding equipment.
• Relevant for industries using resistance welding: automotive, aerospace, heavy machinery, and electrical fabrication.

Related standards

• References IEC 61140 (protection classes) and aligns with ISO/TC 44 (Welding and allied processes) and CEN/TC 121. Users should consult these and any machine‑specific welding standards when applying EN ISO 5826:2014.

Keywords: EN ISO 5826:2014, resistance welding transformers, transformer specifications, transformer‑rectifier, dielectric strength, thermal protection, short‑circuit voltage, welding equipment standards.

Standards Content (Sample)

SLOVENSKI STANDARD
01-maj-2014
1DGRPHãþD
SIST EN ISO 5826:2003
Oprema za uporovno varjenje - Transformatorji - Splošne specifikacije, veljavne za
vse transformatorje (ISO 5826:2014)
Resistance welding equipment - Transformers - General specifications applicable to all
transformers (ISO 5826:2014)
Widerstandsschweißeinrichtungen - Transformatoren - Allgemeine Anforderungen
anwendbar für alle Transformatoren (ISO 5826:2014)
Matériel de soudage par résistance - Transformateurs - Spécifications générales
applicables à tous les transformateurs (ISO 5826:2014)
Ta slovenski standard je istoveten z: EN ISO 5826:2014
ICS:
25.160.30 Varilna oprema Welding equipment
29.180 Transformatorji. Dušilke Transformers. Reactors
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN ISO 5826
NORME EUROPÉENNE
EUROPÄISCHE NORM
February 2014
ICS 25.160.30; 29.180 Supersedes EN ISO 5826:2003
English Version
Resistance welding equipment - Transformers - General
specifications applicable to all transformers (ISO 5826:2014)
Matériel de soudage par résistance - Transformateurs - Widerstandsschweißeinrichtungen - Transformatoren -
Spécifications générales applicables à tous les Allgemeine Anforderungen anwendbar für alle
transformateurs (ISO 5826:2014) Transformatoren (ISO 5826:2014)
This European Standard was approved by CEN on 3 February 2014.

CEN 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 CEN-CENELEC Management Centre or to any CEN 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 CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same
status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United
Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2014 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 5826:2014 E
worldwide for CEN national Members.

Contents Page
Foreword .3
Foreword
This document (EN ISO 5826:2014) has been prepared by Technical Committee ISO/TC 44 “Welding and
allied processes” in collaboration with Technical Committee CEN/TC 121 “Welding and allied processes” the
secretariat of which is held by DIN.
This European Standard shall be given the status of a national standard, either by publication of an identical
text or by endorsement, at the latest by August 2014, and conflicting national standards shall be withdrawn at
the latest by August 2014.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 5826:2003.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech
Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece,
Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom.
Endorsement notice
The text of ISO 5826:2014 has been approved by CEN as EN ISO 5826:2014 without any modification.

INTERNATIONAL ISO
STANDARD 5826
Third edition
2014-02-15
Resistance welding equipment —
Transformers — General
specifications applicable to all
transformers
Matériel de soudage par résistance — Transformateurs —
Spécifications générales applicables à tous les transformateurs
Reference number
ISO 5826:2014(E)
©
ISO 2014
ISO 5826:2014(E)
© ISO 2014
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail [e-mail]
Web www.iso.org
Published in Switzerland
ii © ISO 2014 – All rights reserved

ISO 5826:2014(E)
Contents Page
Foreword .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms . 3
5 Construction, additional equipment. 4
5.1 Thermal protection . 4
5.2 Output current sensing coil . 4
6 Physical environment and operating conditions . 5
6.1 General . 5
6.2 Ambient air temperature . 5
6.3 Humidity . 5
6.4 Altitude . 5
6.5 Transportation and storage . 5
6.6 Provisions for handling . 5
6.7 Cooling liquid temperature . 6
7 Tests . 6
7.1 Test conditions . 6
7.2 Type tests . 6
7.3 Routine tests . 7
8 Protection against electric shock . 7
8.1 Insulation resistance . 7
8.2 Dielectric strength. 7
8.3 Calibration of output current sensing coil . 8
8.4 Protection against electric shock in normal service (direct contact) . 9
8.5 Protection against electric shock in case of fault condition (indirect contact) . 9
8.6 Class II transformer insulation requirements . 9
9 Thermal rating . 9
9.1 General . 9
9.2 Limits of temperature rise .10
9.3 Heating test conditions .11
9.4 Methods of temperature measurements .13
10 Rated output voltage .15
10.1 General .15
10.2 a.c. no-load voltage (U ) .15
10.3 d.c. no-load voltage (U ) .15
2d
11 No-load input current (I ) .15
11.1 General .15
11.2 Measurement procedure .16
12 Short-circuit voltage (U ) .16
cc
13 Output current under load condition .16
14 Cooling liquid circuit .17
15 Dynamic behaviour .17
16 Rating plate .17
16.1 General .17
16.2 Description .18
17 Instruction manual .20
ISO 5826:2014(E)
Annex A (informative) Example of a rating plate .21
Annex B (normative) Corrections for higher altitudes and cooling medium temperatures .22
Annex C (informative) Notes on physical concepts and comments on some definitions .23
Annex D (informative) Type code for single-phase transformers for alternating welding current 29
Bibliography .30
iv © ISO 2014 – All rights reserved

ISO 5826:2014(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2. www.iso.org/directives
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any
patent rights identified during the development of the document will be in the Introduction and/or on
the ISO list of patent declarations received. www.iso.org/patents
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical
Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/TC 44, Welding and allied processes, Subcommittee
SC 6, Resistance welding and allied mechanical joining.
This third edition cancels and replaces the second edition (ISO 5826:1999), which has been technically
revised.
Requests for official interpretations of any aspect of this standard should be directed to the Secretariat
of ISO/TC 44/SC 6 via your national standards body, a complete listing of which can be found at www.
iso.org.
INTERNATIONAL STANDARD ISO 5826:2014(E)
Resistance welding equipment — Transformers — General
specifications applicable to all transformers
1 Scope
This International Standard gives specifications applicable to the following types of transformers for
use in resistance welding equipment:
— single-phase transformers for a.c. welding, typically operating at 50 Hz or 60 Hz;
— single-phase transformers with connected rectifier for d.c. welding, typically operating at 50 Hz or
60 Hz;
— single-phase inverter transformers with connected rectifier for d.c. welding, typically operating at
400 Hz to 2 kHz;
— three-phase transformers with connected rectifier for d.c. welding, typically operating at 50 Hz or
60 Hz.
For the purposes of this International Standard, the term transformer can refer to the transformer alone
or with connected rectifier (transformer-rectifier unit).
This International Standard applies to transformers built to protection class I or II according to IEC 61140.
NOTE The requirements of this International Standard can be supplemented by other resistance welding
transformer standards, e.g. ISO 22829 and ISO 10656.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 669, Resistance welding — Resistance welding equipment — Mechanical and electrical requirements
IEC 60085, Electrical insulation — Thermal evaluation and designation
IEC 60529, Degrees of protection provided by enclosures (IP code)
IEC 61140, Protection against electric shock — Common aspects for installation and equipment
ISO 17657-3, Resistance welding — Welding current measurement for resistance welding — Part 3: Current
sensing coil
ISO 17657-4, Resistance welding — Welding current measurement for resistance welding — Part 4:
Calibration system
ISO 17677-1, Resistance welding — Vocabulary — Part 1: Spot, projection and seam welding
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 17677-1 and ISO 669, and the
following apply.
ISO 5826:2014(E)
3.1
transformer-rectifier unit
transformer with connected rectifier
transformer incorporating a full-wave rectifier in its output circuit
3.2
input voltage
U
RMS value of the voltage applied to the primary terminals of the transformer
3.3
rated supply voltage
U
1N
RMS value of the supply voltage (applied to the input terminals) for which the transformer is constructed
Note 1 to entry: This voltage can be different from the mains voltage.
3.4
d.c. no load voltage
U
2d
for transformers, RMS value of the voltage at the output when a load resistance is connected across the
output terminals
3.5
input current
I
RMS value of the current at the input terminals of the transformer
3.6
output current
I
RMS value of the current at the output terminals of the transformer
3.7
output current at a given duty factor
I
2X
RMS value of the current at the output terminals of the transformer at a duty factor, X
3.8
no-load input current
I
RMS value of the current at the input terminals of the transformer with open circuit output terminals
3.9
permanent input current
I , I
1p Lp
maximum rated value of the current at the input terminals corresponding to the permanent output
current
Note 1 to entry: The relationship between input and output currents depends on the type of transformer.
Note 2 to entry: I is used for single-phase transformers; I is used for three-phase transformers.
1p Lp
2 © ISO 2014 – All rights reserved

ISO 5826:2014(E)
3.10
permanent output current
I
2p
highest output current on all settings of the regulator, for continuous operation (100 % duty factor)
[SOURCE: ISO 669]
Note 1 to entry: The permanent output current is a standardized parameter that is used for comparison and
characterization between different transformers. The value of the permanent output current is dependent on the
test conditions as described in this standard.
3.11
output current under load condition
I
2R
instantaneous RMS value of the output current delivered by the transformer with a load resistance, R
3.12
rated permanent apparent input power
S
1p
rated permanent apparent power calculated by U × I
1N 1p
Note 1 to entry: Welding equipment permanent power, S , determined in accordance with ISO 669, may be different
p
from its welding transformer rated permanent apparent input power, S .
1p
4 Symbols and abbreviated terms
The symbols used in this International Standard are listed in Table 1.
Table 1 — Symbols
Symbol Description Used in [section]
I input current 3.5, 9.3
I no-load input current 3.8, Clause 11
I rated permanent input current (single-phase transformers) 3.9, 9.1, Clause 12
1p
I rated permanent input current (three-phase transformers) 3.9, 9.1
Lp
I output current 3.6, 9.3, Annex C
I permanent output current at 100 % duty factor 3.10, 9.1, 9.3, 16.2, Annex C
2p
I output current on load condition 3.11, Clause 13
2R
I output current at a given duty factor 3.7, Annex C
2X
m mass 16.2
S input power at a given duty factor Annex C
X
S rated permanent apparent input power 3.12, 9.1, 16.2, Annex C
1p
Q rated cooling liquid flow Clause 14, 16.2
R initial resistance of a winding 9.3.5, 9.4.3
R resistance of a winding at end of heating test 9.4.3
T Time Annex C
t on-load time Annex C
T cycle time Annex C
U input voltage 3.2, Clause 13
U rated short-circuit voltage Clause 12, Annex C
cc
U input short-circuit voltage Clause 12
1cc
ISO 5826:2014(E)
Table 1 (continued)
Symbol Description Used in [section]
U rated supply voltage 3.3, 9.1, 9.3, 10.2, 10.3, Clauses
1N
11, 13, 16.2, Annex C
U a.c. no-load voltage 10.1, 10.2, 16.2
U d.c. no-load voltage 3.4, 10.1, 10.3, 16.2
2d
X duty factor 9.3, Annex C
X duty factor of magnetic circuit Annex C
m
Z total impedance referred to output Clauses 12 and 17
Δ pressure drop of cooling liquid circuit Clause 14, 16.2
p
Δθ temperature differences Annex C
1, 2
θ temperature Annex C
θ cooling medium temperature 9.4.3, Annex B, Annex C
a
θ equilibrium temperature Annex C
m
θ temperature when transformer starts to cool Annex C
n
θ temperatures for calculation of thermal time constant or 9.3.5, 9.4.3, Annex C
0, 1, 2
winding temperatures during heating test
τ thermal time constant Annex C
τ thermal time constant at given on-load time Annex C
τ thermal time constant at permanent output current Annex C
2p
5 Construction, additional equipment
5.1 Thermal protection
If the transformer and/or the rectifier are equipped with thermoswitches, they shall have a normally
closed contact. The insulation shall be suitable for the test conditions prescribed in this standard.
5.2 Output current sensing coil
If the transformer is equipped with an output current sensing coil, the degree of protection of an
externally mounted coil shall be lP 55.
The conversion coefficient shall be:
— 50 Hz mains frequency: 150 mV/kA with a load resistance of 1 000 Ω under full sine wave up to
80 °C;
— 60 Hz mains frequency: 180 mV/kA with a load resistance of 1 000 Ω under full sine wave up to
80 °C
The tolerance of the conversion coefficient after mounting in the transformer shall be ± 3 %.
The current sensing coil shall be a Rogowski type. The internal resistance of the current sensing coil
shall be 5 to 50 Ω. White and brown colour coding shall be used for the wiring.
4 © ISO 2014 – All rights reserved

ISO 5826:2014(E)
6 Physical environment and operating conditions
6.1 General
Transformers shall be suitable for use in the physical environment and operating conditions as specified
below.
When the physical environment and/or operating conditions are outside those specified below, an
agreement may be needed between the supplier and the user, (see, for example, IEC 60204-1:1997,
Annex B).
NOTE Examples of these conditions are: outdoor use, different altitude, different temperature of cooling
medium, high humidity, unusually corrosive fumes, steam, excessive oil vapour, abnormal vibration or shock,
excessive dust, unusual sea coast or shipboard conditions.
6.2 Ambient air temperature
Transformers shall be capable of operating correctly in an ambient air temperature between + 5 °C and
+ 40 °C.
In case of other maximum temperatures of the cooling medium, see Annex B.
6.3 Humidity
Transformers shall be capable of operating correctly with a relative humidity up to 95 %.
Harmful effects of condensation shall be avoided by:
— appropriate design of the transformer (e.g. application of electrical potting or encapsulation);
— appropriate design of the welding equipment (e.g. built in heaters, air conditioners, drain holes);
— additional measures (e.g. cooling liquid temperature regulation).
6.4 Altitude
Transformers shall be capable of operating correctly at altitudes up to 1 000 m above mean sea level.
In case of other altitudes, see Annex B.
NOTE At altitudes over 1 000 m, additional electrical safety considerations can be required: see IEC 60664–
1.
6.5 Transportation and storage
Transformers shall be designed to withstand, or suitable precautions shall be taken to protect against,
transportation and storage temperatures between – 25 °C and + 55 °C and for short periods not exceeding
24 h up to + 70 °C. Suitable means shall be provided to prevent damage from humidity, vibration and
shock.
Consideration should be given to frost or freezing protection and draining of the cooling water before
shipping or storage.
6.6 Provisions for handling
Transformers that weigh over 25 kg shall be provided with suitable means for handling by hoists, cranes
or similar equipment such as threaded holes or lifting lugs as appropriate.
ISO 5826:2014(E)
6.7 Cooling liquid temperature
The temperature of the cooling liquid can be up to 30 °C at the inlet of the transformer.
For cooling liquid temperatures above 30 °C, see Annex B.
Condensation caused by high cooling liquid flow or low cooling liquid temperature in relation to the
relative humidity should be prevented.
NOTE For air cooled transformers, see 6.2 and Annex B.
7 Tests
7.1 Test conditions
The tests shall be carried out on a new, dry and completely assembled transformer at an ambient air
temperature between + 10 °C and + 40 °C. The ventilation shall be identical with that prevailing under
normal service conditions. The measuring devices used shall not interfere with the normal ventilation
of the transformer or cause transfer of heat to or from it.
Liquid cooled transformers shall be tested with liquid conditions as specified by the manufacturer.
The accuracy of measuring instruments shall be:
a) electrical measuring instruments: ± 1,0 % full-scale;
b) output current measuring instruments: ± 5 % full-scale, except for instruments used for verification
of the current sensing coil: ± 2 % full scale;
c) temperature measuring devices: ± 2 K.
Unless otherwise specified, the tests required in this International Standard are type tests.
7.2 Type tests
All type tests shall be carried out on the same transformer except otherwise specified.
Those type tests given below shall be carried out in the following sequence without delay between g),
h), i) and j).
a) general visual inspection;
b) insulation resistance (see 8.1) preliminary check;
NOTE The preliminary check on insulation resistance is required to determine whether the transformer
is safe before carrying out the remaining tests.
c) thermal rating (see Clause 9);
d) short-circuit voltage, where applicable (see Clause 12);
e) output current under load condition, where applicable (see Clause 13);
f) protection provided by the enclosure (see 8.4);
g) insulation resistance (see 8.1);
h) dielectric strength (see 8.2);
i) dynamic characteristic, where applicable (see Clause 15);
j) general visual inspection.
6 © ISO 2014 – All rights reserved

ISO 5826:2014(E)
The other tests not mentioned above that are required by this International Standard can be carried out
in any convenient sequence.
7.3 Routine tests
The following routine tests shall be carried out in the sequence given:
a) general visual inspection;
b) dielectric strength (see 8.2);
NOTE The dielectric strength test is required to determine whether the transformer is safe before
carrying out the remaining tests.
c) rated output voltage (see Clause 10);
d) cooling liquid circuit (see Clause 14);
e) general visual inspection.
8 Protection against electric shock
8.1 Insulation resistance
The insulation resistance shall not be less than 50 MΩ.
Compliance is checked by measuring the insulation resistance using a d.c. voltage of 500 V between
a) the input and output windings, and
b) the windings and the frame.
For transformers with connected rectifier, the diodes shall be short circuited during this test.
Liquid-cooled transformers shall be tested without cooling liquid.
8.2 Dielectric strength
The insulation shall withstand the following test voltages without any flashover or breakdown:
a) first test of a welding transformer: test voltages given in Table 2;
b) repetition of the test of the same welding transformer: test voltage 80 % of the values given in
Table 2.
ISO 5826:2014(E)
Table 2 — Dielectric test voltages
c
Maximum a.c. dielectric test voltage
a
rated voltage V
V r.m.s.
r.m.s.
d
Output circuit to input circuit/ Input circuit to transformer frame
thermoswitches and sensing
All circuits
coil circuits to input and out-
put circuits
Class I trans- Class II trans- Grounded frame (accessi- Not grounded, accessible,
b b
formers formers ble or not accessible) or not frame
grounded, not accessible,
frame
Up to 50 250 500 — —
200 1 000 2 000 1 000 2 000
450 1 875 3 750 1 875 3 750
700 2 500 5 000 2 500 5 000
1 000 2 750 5 500 2 750 5 500
NOTE The maximum rated voltage is valid for earthed and unearthed systems.
a
For intermediate values, except between 200 V and 450 V, interpolation of the test voltages is allowed. Interpolation of
the test voltage between 200 V and 450 V is allowed for equipment designed to be installed on delta corner grounded supply
networks only
b
See 8.5.
c
As equipment design is not known, this standard specifies the same value for both input and output circuits. Where no
value is stated, a test may be not be required.
d
Transformer frame can be accessible or not accessible depending on manufacturer installation specifications (i.e.
installation inside enclosures)
The a.c. test voltage shall be of an approximate sine wave-form with a peak value not exceeding 1,45
times the r.m.s. value, having a frequency of approximately 50 Hz or 60 Hz.
The test voltage generator shall deliver the prescribed voltage up to the tripping current. Tripping is
regarded as a flashover or a breakdown. The tripping current setting can be selected according to the
transformer capacitive dispersion current. The maximum permissible setting of the tripping current
shall be 100 mA.
For operator safety, the lowest setting of the tripping current (less than 10 mA) is recommended.
Optionally, testing can be carried out with a d.c. test voltage of 1,4 times the r.m.s. test voltage in
accordance with Table 2.
Transformers with connected rectifier shall be tested after assembly. Rectifiers, their protective devices
and other solid-state electronic components or capacitors, can be short-circuited or disconnected as
required.
Liquid-cooled transformers shall be tested without cooling liquid.
The test voltage may be raised to the full value slowly at the discretion of the manufacturer.
Conformity shall be checked by application of the test voltage for 60 s.
8.3 Calibration of output current sensing coil
Testing shall be carried out in accordance with ISO 17657-3 and ISO 17657-4.
8 © ISO 2014 – All rights reserved

ISO 5826:2014(E)
8.4 Protection against electric shock in normal service (direct contact)
The minimum degree of protection for transformers provided by the enclosure shall be IP 54 as specified
in IEC 60529.
If the transformer is intended to be in-built, the degree of protection may be IP 00.
Compliance shall be verified in accordance with IEC 60529.
8.5 Protection against electric shock in case of fault condition (indirect contact)
Protection against indirect contact is intended to prevent hazardous situations due to an insulation fault
between live parts and exposed conductive parts of the equipment. Protective measures are selected in
welding equipment design. They can include use of transformers with double or reinforced isolation of
the output circuit
NOTE For different types of welding equipment indirect contact protective measures, see IEC 62135–1.
Regarding the output circuit fault condition only, resistance welding transformers are classified as
follows.
a) Class I resistance welding transformers
Transformers with output circuit(s) without any provisions for fault protection. Fault protection is
implemented at welding equipment design by protective bonding or other suitable measures.
b) Class II resistance welding transformers
Transformers with output circuit(s) provided by double or reinforced insulation.
8.6 Class II transformer insulation requirements
The welding circuit shall be designed to electrically isolate the input circuit and all other circuits having
a voltage higher than the no-load voltage by use of reinforced or double insulation.
NOTE Specific requirements for insulation can be found in IEC 62135–1, IEC 60664–1 and IEC 61140.
9 Thermal rating
9.1 General
Thermal rating of the transformer output is specified by the parameter permanent output current, I .
2p
The declared I value is verified by performing the thermal test.
2p
Thermal rating of the transformer input is specified by the parameters permanent input current, I ,
1p
and permanent input power, S .
1p
These parameters are determined by performing a transformer thermal test as specified by this
standard.
The permanent output current, I is an input parameter of the test. For inverter transformers, the
2p,
permanent input current, I , is calculated as I = I / (N /N ), where (N /N ) is the transformer turns
1p 1p 2p 1 2 1 2
ratio. For all other transformers, the permanent input current, I , is measured during the test.
1p
The rated permanent apparent input power, S , is calculated by:
1p
— S = I U (for single-phase transformers);
1p 1p 1n
— S = I U 3 (for three-phase transformers).
1p Lp 1n
ISO 5826:2014(E)
9.2 Limits of temperature rise
9.2.1 General
The thermal requirements for transformers are given as follows:
a) for windings, as specified in 9.2.2;
b) for accessible surfaces, as specified in 9.2.3;
c) for other components, as specified in 9.2.4.
9.2.2 Windings
The temperature rise of the windings shall not exceed the values given in Table 3.
No part shall be allowed to reach any temperature that will damage another part even though that part
might be in compliance with Table 3.
Table 3 — Temperature limits for windings
Limits of temperature rise
Class of insula- Peak tempera-
K
tion in accord- ture in accord-
ance with ance with Air-cooled windings Liquid-cooled windings
IEC 60085 IEC 60076-12
Embedded tem- Resistance Embedded tem- Resistance
°C °C
perature sensor method perature sensor method
105 (A) 150 65 60 75 70
120 (E) 165 80 75 90 85
130 (B) 175 90 80 100 90
155 (F) 190 115 105 125 115
180 (H) 210 140 125 150 135
200 (N) 230 160 145 170 155
220 (R) 250 180 160 190 170
NOTE 1 Surface temperature sensor means that the temperature is measured with non-embedded sensors at
the hottest accessible spot of the outer surface of the windings.
NOTE 2 Normally, the temperature at the surface is the lowest. The temperature determined by resistance
measurement gives the average between all temperatures occurring in a winding. The highest temperature
occurring in the windings (hot spot) can be measured by embedded temperature sensors.
NOTE 3 Other classes of insulation having higher values than those given in Table 3 are available (see
lEC 60085).
NOTE 4 In case of liquid cooled windings the limit of temperature rise should be increased of 10 K.
Compliance is checked by measurement in accordance with 9.3.
9.2.3 Accessible surfaces
The temperature rise of accessible surfaces that can be touched by the equipment operator shall not
exceed the values given in Table 4.
NOTE Transformer surfaces can be accessible or non-accessible depending on manufacturer installation
specifications (i.e. installation inside enclosures).
10 © ISO 2014 – All rights reserved

ISO 5826:2014(E)
Table 4 — Limits of temperature rise for external surfaces
a
External surface Limits of temperature rise
K
Unintentional contact Intentional contact
Bare metal enclosures 40 25
Accessible metallic welding circuit surfaces 45 30
Painted metal enclosures 50 35
Non-metallic enclosures 60 45
a
Values can be increased by 15 K, by agreement between transformer and equipment manufacturers, and the equipment
is specified for use with personal protective equipment (e.g. gloves, protection dresses) or marked with the hot surface
symbol IEC 60417–5041.
9.2.4 Other components
The maximum temperature of other components shall not exceed their rated maximum temperature, in
accordance with the relevant standard. The difference between the temperature of the cooling medium
of the component and its maximum value shall be taken into account.
Rectifiers can be used in the input or output circuit. The temperature reached by the rectifier elements
during the heating test shall not exceed those specified by the manufacturer of the rectifier elements.
Attention is drawn to the intermittent duty characteristic of rectifier elements.
Compliance shall be checked by temperature measurement during the heating test.
9.3 Heating test conditions
9.3.1 General
The test is carried out on a new transformer.
Inverter transformers shall be tested with a load resistor installed at transformer output (see 9.3.3). All
other transformers shall be short circuited at the output. In case of two output windings, the windings
shall be short circuited in parallel.
For transformers with multiple output voltages, the test shall be carried out for the highest voltage
setting.
For liquid cooled transformers, the flow rate shall be set up as specified on the rating plate.
During the last 60 min of the heating test the following tolerances shall be met:
a) output current: ± 2 % of the permanent output current;
b) cooling liquid flow (if applicable): ± 5 % of the rated value.
9.3.2 Test conditions for single-phase transformers for alternating welding current and single-
phase transformers with connected rectifier
The transformer is operated at the permanent output current, I , in one of the following possible
2p
operating conditions:
a) with pulsed output current, using a pulse current corresponding to the maximum short-circuit
current obtained during the test, I , at the duty factor corresponding to the permanent output
current, I , calculated by the formula:
2p
ISO 5826:2014(E)
I
()
2p
X =
I
()
Since pulse duration setting does not influence the test result, the value may be selected to match
equipment and test instrumentation requirements. It is recommended that the pulse duration be
representative of the typical operating condition of the equipment.
b) with permanent output current (100 % duty factor), obtained with reduced transformer supply
voltage, adjusted to obtain the rated permanent output current, I .
2p
9.3.3 Test conditions for single-phase inverter welding transformer with connected rectifier
D.c. current welding transformers operating at medium frequency (inverter equipment) shall be tested
under the following operating conditions:
The input voltage waveform supplying the test object shall be a full wave square waveform at the nominal
transformer supply frequency. The test shall be carried out at the rated supply voltage, U ± 5 %.
1N
The transformer shall be operated with pulses of duration of 240 ms and a duty factor, X, of 20 %.
NOTE 1 These values may need to be adjusted for inverter transformers that are not integrated into welding
guns.
A load resistor shall be installed at transformer output, with a resistance value such that the output
current is limited to
II= 5
22dp
100%
where the term 5 is equal to , 100 % and 20 % being duty factor values.
20%
The output current shall be measured using an integration time equal to the pulse duration (i.e. 240 ms).
NOTE 2 The performance results are only valid up to a duty factor of 20 % but many transformers of this
type are operated at duty factors above 20 %. The manufacturer may supply additional thermal perf
...