IEC 61628-2:1998

Corrugated pressboard and presspaper for electrical purposes - Part 2: Methods of test

Gives test methods (type and dimension of corrugation, dimensional changes on drying, compressive strength and compression modulus) for the materials classified in IEC 61628-1.

Cartons et papiers comprimés ondulés à usages électriques - Partie 2: Méthodes d'essais

Donne des méthodes d'essais (types et dimensions de l'ondulation, variation dimensionnelle au séchage, résistance à la compression et module de compression) applicables aux matériaux définis dans la CEI 61628-1.

General Information

• Status: Published
• Publication Date: 05-Nov-1998
• ICS: 29.035.10 - Paper and board insulating materials
• Technical Committee: TC 15 - Solid electrical insulating materials
• Drafting Committee: MT 14 - TC 15/MT 14
• Current Stage: PPUB - Publication issued
• Start Date: 30-Nov-1998
• Completion Date: 06-Nov-1998

Relations

• Amended By: IEC 61628-2:1998/AMD1:2007 - Amendment 1 - Corrugated pressboard and presspaper for electrical purposes - Part 2: Methods of test
• Effective Date: 05-Sep-2023

Overview

IEC 61628-2:1998 is an International Electrotechnical Commission (IEC) standard that specifies methods of test for corrugated pressboard and presspaper used in electrical applications. As part of the IEC 61628 series, this part focuses on precise testing procedures for evaluating important physical characteristics of these materials. The standard addresses aspects such as corrugation dimensions, moisture content, dimensional changes due to drying, and mechanical strength parameters.

This standard is essential for manufacturers, engineers, and quality control professionals working with electrical insulating materials to ensure consistent quality and performance of corrugated pressboard and presspaper products.

Key Topics

• Type and Dimension of Corrugation: The standard defines detailed measurement methods for key corrugation features:

  • Wavelength: Measuring multiple wavelengths over a sample to determine average size.
  • Amplitude: Assessing the height difference between peaks and troughs.
  • Length of Horizontal Parts: Measuring flat parts in the corrugation profile.
  • Angle of Slope: Using precise protractors to determine slope angles.
  • Thickness of Board: Measuring at flat or inflection points, avoiding pressure-influenced spots.

• Moisture Content: Determined according to the referenced IEC 60641-2 methods, crucial for understanding material behavior and stability in electrical environments.

• Dimensional Changes on Drying: Tests to quantify how corrugation amplitude and other dimensions change after drying, indicating stability and reliability under temperature variations.

• Compressive Strength and Compression Modulus: Mechanical testing to assess the material's ability to withstand pressure and maintain structural integrity.

• Conductivity of Aqueous Extract: Evaluating electrical properties related to insulation performance.

Applications

IEC 61628-2 is applied in the production, quality control, and certification of corrugated pressboard and presspaper materials used as insulating components in electrical equipment. Typical applications include:

• Insulation in transformers, switchgear, and electrical machines.
• Material selection and verification in manufacturing of electrical protective components.
• Compliance testing during product development and before market release to meet international quality standards.
• Ensuring reliable performance of electrical insulation under mechanical load and environmental stress.

By implementing IEC 61628-2 test methods, manufacturers can guarantee materials are produced to internationally recognized benchmarks, improving safety, durability, and operational efficiency in electrical installations.

Related Standards

• IEC 61628-1: Corrugated pressboard and presspaper for electrical purposes – Part 1: Definitions, designations, and general requirements. Provides the classification framework for which IEC 61628-2 establishes detailed testing.

• IEC 61628-3 (under consideration): Specifies requirements for individual corrugated pressboard and presspaper materials following the testing protocols.

• IEC 60641-2: Pressboard and presspaper for electrical purposes – Part 2: Methods of test. Referenced by IEC 61628-2 for conditioning specimens and moisture content determination.

• Related IEC standards on insulating materials and electrical insulating tests, which complement IEC 61628 series for comprehensive material specification.

---

Keywords: IEC 61628-2, corrugated pressboard, presspaper, electrical insulation, methods of test, corrugation dimensions, moisture content, compressive strength, dimensional stability, electrical insulating materials, IEC standards.

Standards Content (Sample)

NORME
CEI
INTERNATIONALE
IEC
61628-2
INTERNATIONAL
Première édition
STANDARD
First edition
1998-11
Cartons et papiers comprimés ondulés
à usages électriques –
Partie 2:
Méthodes d’essais
Corrugated pressboard and presspaper
for electrical purposes –
Part 2:
Methods of test
Numéro de référence
Reference number
CEI/IEC 61628-2:1998
Numéros des publications Numbering
Depuis le 1er janvier 1997, les publications de la CEI As from 1 January 1997 all IEC publications are
sont numérotées à partir de 60 000. issued with a designation in the 60 000 series.
Publications consolidées Consolidated publications
Les versions consolidées de certaines publications de Consolidated versions of some IEC publications
la CEI incorporant les amendements sont disponibles. including amendments are available. For example,
Par exemple, les numéros d’édition 1.0, 1.1 et 1.2 edition numbers 1.0, 1.1 and 1.2 refer, respectively, to
indiquent respectivement la publication de base, la the base publication, the base publication incor-
publication de base incorporant l’amendement 1, et porating amendment 1 and the base publication
la publication de base incorporant les amendements 1 incorporating amendments 1 and 2.
et 2.
Validité de la présente publication Validity of this publication
Le contenu technique des publications de la CEI est The technical content of IEC publications is kept under
constamment revu par la CEI afin qu'il reflète l'état constant review by the IEC, thus ensuring that the
actuel de la technique. content reflects current technology.
Des renseignements relatifs à la date de re- Information relating to the date of the reconfirmation of
confirmation de la publication sont disponibles dans the publication is available in the IEC catalogue.
le Catalogue de la CEI.
Les renseignements relatifs à des questions à l’étude et Information on the subjects under consideration and
des travaux en cours entrepris par le comité technique work in progress undertaken by the technical com-
qui a établi cette publication, ainsi que la liste des mittee which has prepared this publication, as well as
publications établies, se trouvent dans les documents the list of publications issued, is to be found at the
ci-dessous: following IEC sources:
• «Site web» de la CEI* • IEC web site*
• Catalogue des publications de la CEI • Catalogue of IEC publications
Publié annuellement et mis à jour régulièrement Published yearly with regular updates
(Catalogue en ligne)* (On-line catalogue)*
• Bulletin de la CEI • IEC Bulletin
Disponible à la fois au «site web» de la CEI* Available both at the IEC web site* and
et comme périodique imprimé as a printed periodical
Terminologie, symboles graphiques Terminology, graphical and letter
et littéraux symbols
En ce qui concerne la terminologie générale, le lecteur For general terminology, readers are referred to
se reportera à la CEI 60050: Vocabulaire Electro- IEC 60 050: International Electrotechnical Vocabulary
technique International (VEI). (IEV).
Pour les symboles graphiques, les symboles littéraux For graphical symbols, and letter symbols and signs
et les signes d'usage général approuvés par la CEI, le approved by the IEC for general use, readers are
lecteur consultera la CEI 60027: Symboles littéraux à referred to publications IEC 60027: Letter symbols to
utiliser en électrotechnique, la CEI 60417: Symboles be used in electrical technology, IEC 60417: Graphical
graphiques utilisables sur le matériel. Index, relevé et symbols for use on equipment. Index, survey and
compilation des feuilles individuelles, et la CEI 60617: compilation of the single sheets and IEC 60617:
Symboles graphiques pour schémas. Graphical symbols for diagrams.
* Voir adresse «site web» sur la page de titre. * See web site address on title page.

NORME
CEI
INTERNATIONALE
IEC
61628-2
INTERNATIONAL
Première édition
STANDARD
First edition
1998-11
Cartons et papiers comprimés ondulés
à usages électriques –
Partie 2:
Méthodes d’essais
Corrugated pressboard and presspaper
for electrical purposes –
Part 2:
Methods of test
 IEC 1998 Droits de reproduction réservés  Copyright - all rights reserved
Aucune partie de cette publication ne peut être reproduite ni No part of this publication may be reproduced or utilized in
utilisée sous quelque forme que ce soit et par aucun any form or by any means, electronic or mechanical,
procédé, électronique ou mécanique, y compris la photo- including photocopying and microfilm, without permission in
copie et les microfilms, sans l'accord écrit de l'éditeur. writing from the publisher.
International Electrotechnical Commission 3, rue de Varembé Geneva, Switzerland
Telefax: [phone] e-mail: [e-mail] IEC web site http: //www.iec.ch
CODE PRIX
Commission Electrotechnique Internationale
PRICE CODE M
International Electrotechnical Commission
Pour prix, voir catalogue en vigueur
For price, see current catalogue

– 2 – 61628-2 © CEI:1998
SOMMAIRE
Pages
AVANT-PROPOS . 4
INTRODUCTION . 6
Articles
1 Domaine d'application . 8
2 Référence normative. 8
3 Note générale sur les essais . 8
4 Type et dimension de l'ondulation. 8
5 Teneur en humidité . 12
6 Variation dimensionnelle au séchage. 12
7 Résistance à la compression et module de compression. 14
8 Conductivité de l'extrait aqueux . 18
Figures. 20

61628-2 © IEC:1998 – 3 –
CONTENTS
Page
FOREWORD . 5
INTRODUCTION . 7
Clause
1 Scope. 9
2 Normative reference. 9
3 General note on tests . 9
4 Type and dimension of corrugation . 9
5 Moisture content. 13
6 Dimensional changes on drying . 13
7 Compressive strength and compression modulus . 15
8 Conductivity of aqueous extract . 19
Figures. 21

– 4 – 61628-2 © CEI:1998
COMMISSION ÉLECTROTECHNIQUE INTERNATIONALE
________
CARTONS ET PAPIERS COMPRIMÉS ONDULÉS
À USAGES ÉLECTRIQUES –
Partie 2: Méthodes d'essais
AVANT-PROPOS
1) La CEI (Commission Electrotechnique Internationale) est une organisation mondiale de normalisation composée
de l'ensemble des comités électrotechniques nationaux (Comités nationaux de la CEI). La CEI a pour objet de
favoriser la coopération internationale pour toutes les questions de normalisation dans les domaines de
l'électricité et de l'électronique. A cet effet, la CEI, entre autres activités, publie des Normes internationales.
Leur élaboration est confiée à des comités d'études, aux travaux desquels tout Comité national intéressé par le
sujet traité peut participer. Les organisations internationales, gouvernementales et non gouvernementales, en
liaison avec la CEI, participent également aux travaux. La CEI collabore étroitement avec l'Organisation
Internationale de Normalisation (ISO), selon des conditions fixées par accord entre les deux organisations.
2) Les décisions ou accords officiels de la CEI concernant les questions techniques représentent, dans la mesure
du possible un accord international sur les sujets étudiés, étant donné que les Comités nationaux intéressés
sont représentés dans chaque comité d’études.
3) Les documents produits se présentent sous la forme de recommandations internationales. Ils sont publiés
comme normes, rapports techniques ou guides et agréés comme tels par les Comités nationaux.
4) Dans le but d'encourager l'unification internationale, les Comités nationaux de la CEI s'engagent à appliquer de
façon transparente, dans toute la mesure possible, les Normes internationales de la CEI dans leurs normes
nationales et régionales. Toute divergence entre la norme de la CEI et la norme nationale ou régionale
correspondante doit être indiquée en termes clairs dans cette dernière.
5) La CEI n’a fixé aucune procédure concernant le marquage comme indication d’approbation et sa responsabilité
n’est pas engagée quand un matériel est déclaré conforme à l’une de ses normes.
6) L’attention est attirée sur le fait que certains des éléments de la présente Norme internationale peuvent faire
l’objet de droits de propriété intellectuelle ou de droits analogues. La CEI ne saurait être tenue pour
responsable de ne pas avoir identifié de tels droits de propriété et de ne pas avoir signalé leur existence.
La Norme internationale CEI 61628-2 a été établie par le sous-comité 15C: Spécifications, du
comité d’études 15 de la CEI: Matériaux isolants.
Le texte de cette norme est issu des documents suivants:
FDIS Rapport de vote
15C/992/FDIS 15C/1008/RVD
Le rapport de vote indiqué dans le tableau ci-dessus donne toute information sur le vote ayant
abouti à l'approbation de cette norme.

61628-2 © IEC:1998 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
________
CORRUGATED PRESSBOARD AND PRESSPAPER
FOR ELECTRICAL PURPOSES –
Part 2: Methods of test
FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of the 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, the IEC publishes International Standards. 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. The 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 the 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 National Committees.
3) The documents produced have the form of recommendations for international use and are published in the form
of standards, technical reports or guides and they are accepted by the National Committees in that sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with one of its standards.
6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject
of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61628-2 has been prepared by subcommittee 15C: Specifications,
of IEC technical committee 15: Insulating materials.
The text of this standard is based on the following documents:
FDIS Report on voting
15C/992/FDIS 15C/1008/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.

– 6 – 61628-2 © CEI:1998
INTRODUCTION
La présente partie de la CEI 61628 fait partie d'une série traitant des cartons et des papiers
comprimés ondulés à usages électriques.
Cette série comprend trois parties:
– CEI 61628-1:1997, Cartons et papiers comprimés ondulés à usages électriques – Partie 1:
Définitions, désignations et prescriptions générales
– CEI 61628-2:1998, Cartons et papiers comprimés ondulés à usages électriques – Partie 2:
Méthodes d'essais
– CEI 61628-3,— Cartons et papiers comprimés ondulés à usages électriques – Partie 3:
Spécifications pour matériaux particuliers, (à l'étude)

61628-2 © IEC:1998 – 7 –
INTRODUCTION
This part of IEC 61628 is one of a series which deals with corrugated pressboard and
presspaper for electrical purposes.
This series consists of three parts:
– IEC 61628-1:1997, Corrugated pressboard and presspaper for electrical purposes – Part 1:
Definitions, designations and general requirements
– IEC 61628-2:1998, Corrugated pressboard and presspaper for electrical purposes – Part 2:
Methods of test
– IEC 61628-3,— Corrugated pressboard and presspaper for electrical purposes – Part 3:
Specification for individual materials (under consideration)

– 8 – 61628-2 © CEI:1998
CARTONS ET PAPIERS COMPRIMÉS ONDULÉS
À USAGES ÉLECTRIQUES –
Partie 2: Méthodes d’essais
1 Domaine d'application
La présente partie de la CEI 61628 donne les méthodes d'essais applicables au matériel défini
.
dans la CEI 61628-1
2 Référence normative
Le document normatif suivant contient des dispositions qui, par suite de la référence qui y est
faite, constituent des dispositions valables pour la présente partie de la CEI 61628. Pour les
références datées, les amendements ultérieurs ou les révisions de ces publications ne
s’appliquent pas. Toutefois, les parties prenantes aux accords fondés sur la présente partie de
la CEI 61628 sont invitées à rechercher la possibilité d’appliquer les éditions les plus récentes
du document normatif indiqué ci-après. Pour les références non datées, la dernière édition du
document normatif en référence s’applique. Les membres de l’ISO et de la CEI possèdent le
registre des Normes internationales en vigueur.
CEI 60641-2:1979, Spécifications pour le carton comprimé et le papier comprimé à usages
électriques – Deuxième partie: Méthodes d'essai
Amendement 1 (1993)
3 Note générale sur les essais
Pour prélever les éprouvettes, il est recommandé d'utiliser une scie à ruban à grande vitesse
ayant une largeur de coupe inférieure à 1 mm. Il convient que les bavures résultant de la
découpe soient soigneusement éliminées.
Sauf indications contraires, les éprouvettes doivent, après découpe, être conditionnées selon
article 1 de la CEI 60641-2.
4 Type et dimension de l'ondulation
La forme et le type de l'ondulation sont définis par la longueur d'onde, l'amplitude maximale, la
longueur des parties horizontales, l'angle de pente et l'épaisseur du carton à partir duquel est
réalisé le matériau ondulé (voir figures 1a et 1b).
Les essais suivants sont réalisés sur le matériau en l'état de réception.
4.1 Longueur d'onde
4.1.1 Procédure
Prélever au moins trois éprouvettes, ayant chacune une longueur supérieure à trois fois la
longueur d'onde.
A l'aide d'un crayon repérer le début de la première longueur d'onde et la fin de la dernière
longueur d'onde (au minimum trois longueurs d'ondes).

61628-2 © IEC:1998 – 9 –
CORRUGATED PRESSBOARD AND PRESSPAPER
FOR ELECTRICAL PURPOSES –
Part 2: Methods of test
1 Scope
This part of IEC 61628 gives methods of test applicable for the materials classified in
IEC 61628-1.
2 Normative reference
The following normative document contains provisions which, through reference in this text,
constitutes provisions of this part of IEC 61628. For dated references, subsequent
amendments to, or revisions of, any of these publications do not apply. However, parties to
agreements based on this part of IEC 61628 are encouraged to investigate the possibility of
applying the most recent editions of the normative document indicated below. For undated
references, the latest edition of the normative document referred to applies. Members of ISO
and IEC maintain registers of currently valid International Standards.
IEC 60641-2:1979, Specification for pressboard and presspaper for electrical purposes – Part 2:
Method of test
Amendment 1 (1993)
3 General note on tests
It is recommended to use a high-speed band saw with a cut width less than 1 mm to make the
test specimens. The burrs made by cutting should be carefully removed.
Unless otherwise specified, the test specimens after being cut, shall be conditioned according
to IEC 60641-2, clause 1.
4 Type and dimension of corrugation
The shape and type of corrugation are defined by wavelength, maximum amplitude, the length
of horizontal parts, angle of slope and the board thickness out of which the corrugated material
is made (see figures 1a and 1b).
The following tests are made on the material as received.
4.1 Wavelength
4.1.1 Procedure
Cut at least three test samples, each test sample having a length greater than three complete
wavelengths.
With a pencil, mark the starting line of the first wavelength and the end line of the last
wavelength (minimum three wavelengths).

– 10 – 61628-2 © CEI:1998
(Le début et la fin de la longueur d'onde sont choisis de préférence comme le point d'amplitude
maximale pour une ondulation du type sinusoïdal et le centre de la partie horizontale pour une
ondulation du type anguleux.)
Poser l'éprouvette sur une surface plane sans lui appliquer de contrainte.
A l'aide d'une règle précise à 0,5 mm près, mesurer la distance entre les repères.
Diviser la valeur mesurée par le nombre de longueurs d'onde entre les repères.
4.1.2 Résultats
Noter les valeurs moyenne, minimale et maximale des mesures.
4.2 Amplitude
4.2.1 Procédure
Prélever au moins neuf éprouvettes, ayant chacune une largeur de (100 ± 10) mm et une
longueur de une fois et demie à deux fois la longueur d'onde de façon à y inclure deux
sommets inférieurs complets.
Poser l'éprouvette sur une surface plane sans lui appliquer de contrainte.
A l'aide d'une jauge de profondeur (précise à 0,1 mm près), mesurer la distance entre le point
le plus haut et le point le plus bas.
4.2.2 Résultats
Noter les valeurs moyenne, minimale et maximale des mesures.
4.3 Longueur de la partie horizontale de l'ondulation
4.3.1 Procédure
A l'aide d'un crayon, repérer sur au moins trois ondulations différentes, la projection verticale du
point d'intersection théorique des parties obliques et horizontales de l'ondulation. Ce repérage
doit se situer sur une ligne parallèle à la direction des longueurs d'ondes. Mesurer la distance
entre les repérages à l'aide d'un pied à coulisse précis à 0,1 mm près (distance E de la figure 1b).
Répéter cette mesure sur la partie opposée de la feuille afin de mesurer la distance D de la
figure 1b.
Les valeurs de D et de E pouvant être différentes intentionnellement, il convient de noter les
deux valeurs.
4.3.2 Résultats
Noter les valeurs moyenne, minimale et maximale des valeurs mesurées pour D et pour E.
4.4 Angle de pente
4.4.1 Procédure
Prélever au moins trois éprouvettes, ayant chacune une largeur de (100 ± 10) mm et une
longueur de une fois et demie à deux fois la longueur d'onde de façon à y inclure deux
sommets inférieurs complets.
61628-2 © IEC:1998 – 11 –
(The best starting and end line of a wavelength is the line of maximum amplitude for a sine
type corrugation and the centre of a horizontal part in an angular type corrugation.)
Lay the test sample on a flat surface with no strain applied.
Measure with a ruler (precise to 0,5 mm) the distance between the pencil lines.
Divide the measured value by the number of wavelengths between the lines.
4.1.2 Results
Report the mean, minimum and maximum values of the measurements.
4.2 Amplitude
4.2.1 Procedure
Cut at least nine specimens, each being (100 ± 10) mm wide, and one-and-a-half to two
wavelengths in length, so that two full bottom peaks are included.
Lay the test specimens on a flat surface with no strain applie
...

IEC 61628-2 ®
Edition 1.1 2007-07
CONSOLIDATED VERSION
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Corrugated pressboard and presspaper for electrical purposes –
Part 2: Methods of test
Cartons et papiers comprimés ondulés à usages électriques –
Partie 2: Méthodes d’essais
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IEC 61628-2 ®
Edition 1.1 2007-07
CONSOLIDATED VERSION
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Corrugated pressboard and presspaper for electrical purposes –

Part 2: Methods of test
Cartons et papiers comprimés ondulés à usages électriques –

Partie 2: Méthodes d’essais
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.035.10 ISBN 2-8318-9236-8

– 2 – 61628-2 © IEC:1998+A1:2007
CONTENTS
FOREWORD.3
INTRODUCTION.5

1 Scope.6
2 Normative reference .6
3 General note on tests.6
4 Type and dimension of corrugation.6
5 Moisture content .8
6 Dimensional changes on drying.8
7 Compressive strength and compression modulus .9
8 Conductivity of aqueous extract .11

Figure 1 – Different types of corrugation.12
Figure 2 – Positioning of the test specimen.13
Figure 3 – Test specimen holder – Side view.13
Figure 4 – Curve of deflection versus force.14

61628-2 © IEC:1998+A1:2007 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
________
CORRUGATED PRESSBOARD AND PRESSPAPER
FOR ELECTRICAL PURPOSES –
Part 2: Methods of test
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 provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
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.
This consolidated version of the official IEC Standard and its amendment has been
prepared for user convenience.
IEC 61628-2 edition 1.1 contains the first edition (1998) [documents 15C/992/FDIS and
15C/1008/RVD] and its amendment 1 (2007) [documents 15/293/CDV and 15/340/RVC].
A vertical line in the margin shows where the base publication has been modified by
amendment 1.
International Standard IEC 61628-2 has been prepared by subcommittee 15C: Specifications,
of IEC technical committee 15: Insulating materials.

– 4 – 61628-2 © IEC:1998+A1:2007
The committee has decided that the contents of the base publication and its amendments will
remain unchanged until the maintenance result 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.
61628-2 © IEC:1998+A1:2007 – 5 –
INTRODUCTION
This part of IEC 61628 is one of a series which deals with corrugated pressboard and
presspaper for electrical purposes.
This series consists of three parts:
– IEC 61628-1:1997, Corrugated pressboard and presspaper for electrical purposes – Part 1:
Definitions, designations and general requirements
– IEC 61628-2:1998, Corrugated pressboard and presspaper for electrical purposes – Part 2:
Methods of test
– IEC 61628-3,— Corrugated pressboard and presspaper for electrical purposes – Part 3:
Specification for individual materials (under consideration)

– 6 – 61628-2 © IEC:1998+A1:2007
CORRUGATED PRESSBOARD AND PRESSPAPER
FOR ELECTRICAL PURPOSES –
Part 2: Methods of test
1 Scope
This part of IEC 61628 gives methods of test applicable for the materials classified in
IEC 61628-1.
2 Normative reference
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 60641-2:2004, Pressboard and presspaper for electrical purposes – Part 2: Methods of
test
3 General note on tests
It is recommended to use a high-speed band saw with a cut width less than 1 mm to make the
test specimens. The burrs made by cutting should be carefully removed.
Unless otherwise specified, the test specimens after being cut, shall be conditioned according
to IEC 60641-2.
4 Type and dimension of corrugation
The shape and type of corrugation are defined by wavelength, maximum amplitude, the length
of horizontal parts, angle of slope and the board thickness out of which the corrugated material
is made (see figures 1a and 1b).
The following tests are made on the material as received.
4.1 Wavelength
4.1.1 Procedure
Cut at least three test samples, each test sample having a length greater than three complete
wavelengths.
With a pencil, mark the starting line of the first wavelength and the end line of the last
wavelength (minimum three wavelengths).
(The best starting and end line of a wavelength is the line of maximum amplitude for a sine
type corrugation and the centre of a horizontal part in an angular type corrugation.)
Lay the test sample on a flat surface with no strain applied.

61628-2 © IEC:1998+A1:2007 – 7 –
Measure with a ruler (precise to 0,5 mm) the distance between the pencil lines.
Divide the measured value by the number of wavelengths between the lines.
4.1.2 Results
Report the mean, minimum and maximum values of the measurements.
4.2 Amplitude
4.2.1 Procedure
Cut at least nine specimens, each being (100 ± 10) mm wide, and one-and-a-half to two
wavelengths in length, so that two full bottom peaks are included.
Lay the test specimens on a flat surface with no strain applied.
With a gauge (precise to 0,1 mm), measure the distance between the highest point and the
lowest point.
4.2.2 Results
Report the mean, minimum and maximum values of the measurements.
4.3 Length of horizontal parts of corrugation
4.3.1 Procedure
On at least three different corrugations, mark with a pencil the vertical projections of the
theoretical points where the oblique parts of the corrugation meet the horizontal part. The
pencil marks shall be positioned on a line in the direction of the corrugation wavelength.
Measure the distance between the pencil marks with a calliper precise to 0,1 mm (distance E in
figure 1b).
Repeat the measurements at the opposite side of the sheet to measure the distance D in
figure 1b.
Because D and E may be intentionally different, both measurements shall be reported.
4.3.2 Results
Report for D and E the mean, minimum and maximum values of the measurements.
4.4 Angle of slope
4.4.1 Procedure
Cut at least three specimens, each being (100 ± 10) mm wide, and one-and-a-half to two
wavelengths in length, so that two full bottom peaks are included.
Lay the test sample on a flat surface with no strain applied.
α of the central
With an adequate protractor (precise to 0,5°), measure the two angles
corrugation.
– 8 – 61628-2 © IEC:1998+A1:2007
4.4.2 Results
Report the mean, minimum and maximum values of the measurements.
4.5 Thickness of board
4.5.1 Procedure
With an external screw type micrometer as described in IEC 60641-2, make at least nine
different measurements of the board thickness with an accuracy of ± 0,01 mm at points where
the corrugation curve is flat, or in the area of the inflection point for a sine type corrugation.
NOTE Measures on the horizontal flat part should be avoided as the board thickness may have been affected by
the direct action of the forming press when mechanical pressure has been used to manufacture the corrugated
material.
4.5.2 Results
Report the mean, minimum and maximum values of the measurements.
5 Moisture content
Moisture content shall be determined according to IEC 60641-2.
6 Dimensional changes on drying
6.1 Change of amplitude
6.1.1 Procedure (see figure 2)
Cut three specimens (50 ± 5) mm wide and five wavelengths long and condition them
according to IEC 60641-2.
Place the specimens on a flat steel plate the dimensions of which shall exceed the dimensions
of the specimen by at least 50 mm. Place a second flat rigid plate of calibrated thickness T,
50 mm wide and of sufficient length to cover all the corrugations, on top of the specimen. The
weight of this plate shall guarantee that all the corrugations are in flat contact with both top and
bottom plate and shall be defined in the specification sheets of IEC 61628-3.
NOTE The weight of the plate can be adjusted by additional weights added on top of it.
If all the corrugations of any specimen are not in contact with top and bottom plate under this
pre-load, the specimen shall be discarded.
The amplitude of the corrugation of the specimen is measured by means of a gauge precise to
0,1 mm with a semi-spherical sensor in the following way:
– lower the sensor of the gauge on to the bottom steel plate and adjust the pointer to zero;
– set the sensor on the top plate and read the measured values at three different points near
the centre of the plate and form the mean of these three measures.
Record this value as value B for each specimen.
Remove and dry the test specimens in a ventilated oven at 105 °C ± 5 K for (48 ± 1) h. After
cooling at room temperature in a desiccator, repeat the measurements as above.
Record for each specimen the new value as C.

61628-2 © IEC:1998+A1:2007 – 9 –
6.1.2 Calculation
The change of amplitude is calculated as a percentage of the original amplitude and is given by
the formula:
CB−
change of amplitude = × 100
BT−
There is normally an increase of amplitude after drying.
6.1.3 Results
Report the mean value obtained. Minimum and maximum values should also be reported.
6.2 Lengthwise and crosswise dimensional changes
6.2.1 Procedure
Cut three specimens (250 ± 0,5) mm × (250 ± 0,5) mm and condition them according to
IEC 60641-2. Place the specimen on a flat steel plate of at least 300 mm × 300 mm. A second
flat rigid plate of the same dimension is placed on top of the specimen. Its mass, which will be
defined in the specification sheets of IEC 61628-3, shall guarantee that all corrugations are in
contact with both top and bottom plates.
Measure the lengthwise and crosswise dimensions with a calliper precise to 0,1 mm (or
equivalent) at two different positions.
Record the mean value of the two measurements as the initial dimensions of the specimen.
Remove and dry the test specimens in a ventilated oven at 105 °C ± 5 K for (48 ± 1) h. After
cooling at room temperature in a desiccator, repeat the measurements as above.
6.2.2 Results
The dimensional changes lengthwise and crosswise are calculated for each specimen as the
per cent change in dimensions from those of the original conditioned specimen. Report all
calculated values and the means of the lengthwise and crosswise values.
7 Compressive strength and compression modulus
7.1 Purpose and principle of the test
The purpose of the test is to calculate the compressive strength and the compression modulus
of the material when the corrugation is submitted to a force applied on the corrugation and
perpendicular to the original plane of the corrugated material.
The perpendicular force is applied with the ends of the test specimens subjected to total
restraint (see figure 3).
– 10 – 61628-2 © IEC:1998+A1:2007
7.2 Test specimens
Cut five test specimens (50 ± 0,5) mm wide and five full wavelengths long unless the
wavelength is <10 mm, in which case a number of wavelengths to give a total length ≥50 mm
shall be used. If the wavelength is >60 mm, it is permitted to use three full wavelengths instead
of five. The ends of the test specimens are cut within 1 mm of the crest of a corrugation, or in
case of a angular type corrugation, within 1 mm of the centre line of a flat horizontal part.
The two end cuts shall be parallel to the corrugation and to each other within 0,1 mm.
Condition the test specimens in accordance with IEC 60641-2.
7.3 Test apparatus
The test apparatus shall consist of:
– a compression tester which will measure and record graphically the applied force with an
accuracy of ±1 % and the crosshead movement with a magnification of at least 10 times.
The crosshead speed shall be such that the end point of the test is reached within 10 s
to 30 s;
– a test specimen holder, (an example is shown in figure 3);
– a pressure plate whose dimensions cover completely all the crests of the specimen's
corrugations.
7.4 Procedure
– Place the test specimen in the test holder.
– Adjust the mobile end of the holder so that both ends touch evenly the ends of the test
specimen without exerting any lateral force.
– Place the pressure plate on the test specimen.
– With a calliper precise to 0,1 mm, measure the distance L between the pressure plate and
the bottom end part of the holder. Six measurements shall be made: three on each side of
the test specimen, one at each end and one at the centre of each side. L shall be recorded
as the mean value of these six measurements.
NOTE The pressure plate should be centred approximately on the test specimen and the pressure foot applied
centrally to the pressure plate. The offset of the axis of the load application from the centre of the test specimen
should be less than 5 mm.
– Record the force and the crosshead movement up to the point when the force increases
sharply after collapse (see figure 4).
7.5 Calculation
The force of failure is the value of the force at the first turning point (maximum or point of
inflection) at each force/movement graph.
The compressive strength of the test specimen is the force at failure divided by the projected
area of the test specimen and is usually expressed in megapascals (MPa).
The compression modulus is calculated as follows:
On the graph (see figure 4) mark the points A and B where the force reaches 25 % and 50 % of
the force at failure. Draw a straight line through A and B. This line crosses the deflection axis
at point C, at a distance λ from the origin.

61628-2 © IEC:1998+A1:2007 – 11 –
This value λ represents the settling of the test specimen when applying the force and is due to
the unevenness of the corrugation.
Δl is the difference between the deflection of the test specimen at point B and the deflection at
point A.
ΔF is the variation of the force between point B and point A.
The compression modulus is given by the formula:
Δ F
compression modulus =
Δ I
× S
L − λ
The value is e
...