IEC 60740-1:2005

Laminations for transformers and inductors - Part 1: Mechanical and electrical characteristics

IEC 60740-1:2005 specifies the characteristics of laminations. Their preferred use is cores for transformers and inductors. The laminations are made of sheets and strips of magnetic materials, specified in IEC 60404-8-4 and IEC 60404-8-7. The main changes are listed below:
a) ranges with lamination strips YS, YSUI 1, YSUI 2 and laminations YEE 2-..L added;
b) range YEI 1 extended at the above end;
c) ranges YED 2, YEF 2, YEL 2, YES 2, Type YM 1-5a and YM 1-7a cancelled;
d) national designations cancelled;
e) electrical characteristics for the laminations specified;
f) mechanical characteristics for laminations added;
g) holes added for lamination types YEI 1, YUI 1, YUI 2, YM 1;
h) in Annex A, a conversion of the polarisation J and the field strength H in a specific total apparent power is defined. For the characteristics of the reactive power and the power loss, equations and constants are specified.

Tôles découpées pour transformateurs et inductances - Partie 1: Caractéristiques électriques et mécaniques

La CEI 60740-1:2005 spécifie les caractéristiques de tôles découpées. Leur utilisation préférentielle porte sur les noyaux de transformateur et d'inductances. Les tôles découpées sont constituées de bandes et de tôles de matériaux magnétiques, spécifiées dans la CEI 60404-8-4 et la CEI 60404-8-7. Les principales modifications sont présentées ci-après:
a) gammes avec bandes de tôles découpées YS, YSUI 1, YSUI 2 et tôles découpées YEE 2 -..L ajoutées;
b) gamme YEI 1 étendue aux fins de la présente norme;
c) gammes YED 2, YEF 2, YEL 2, YES 2, Type YM 1-5a et YM 1-7a annulées;
d) désignations nationales annulées;
e) caractéristiques électriques pour les tôles découpées spécifiées;
f) caractéristiques mécaniques pour les tôles découpées ajoutées;
g) trous ajoutés pour les tôles découpées de type YEI 1, YUI 1, YUI 2 et YM 1;
h) conversion de la polarisation J et de l'intensité du champ H en une puissance apparente totale spécifique définie à l'Annexe A. Des équations et des constantes sont spécifiées pour les caractéristiques de la puissance réactive et de la perte de puissance.

General Information

• Status: Published
• Publication Date: 08-Aug-2005
• ICS: 29.100.10 - Magnetic components
• Technical Committee: TC 51 - Magnetic components, ferrite and magnetic powder materials
• Current Stage: PPUB - Publication issued
• Start Date: 09-Aug-2005
• Completion Date: 30-Nov-2005

Overview

IEC 60740-1:2005 - "Laminations for transformers and inductors – Part 1: Mechanical and electrical characteristics" defines the mechanical and electrical requirements for lamination sheets and strips used to make cores for transformers and inductors. It covers material selection (referencing IEC 60404-8-4 and IEC 60404-8-7), dimensional standards, test methods, and electrical characteristics such as specific total apparent power and power loss. Annex A provides conversions between polarization (J), field strength (H) and specific apparent power, plus equations and constants for reactive power and losses.

Keywords: IEC 60740-1, laminations for transformers, laminations for inductors, mechanical characteristics, electrical characteristics, silicon steel, core loss, lamination strips

Key topics and technical requirements

• Materials and thicknesses: Preferred magnetic steels and alloys, nominal lamination thicknesses and stacking factors (see Tables for material classes).
• Designation and shapes: Standardized lamination and strip types (YEI, YUI, YEE, YEx, YM, YS etc.), including added ranges and cancelled types per the 2005 edition.
• Dimensions and tolerances: Detailed dimensions, symmetry and tolerance rules for many lamination shapes and strip types.
• Electrical measurements: Procedures for measuring power loss, total apparent power and amplitude permeability at low, medium and high field strengths; test-coil and test-core conditions; harmonic content limits.
• Core constants and effective parameters: Methods to determine magnetic path length, core cross-section, and effective parameters for different lamination types.
• Mechanical characteristics and quality: Requirements for appearance, cut and punch edge, camber, distortion, bending, insulation, and welding tests.
• Packing and marking: Rules for packing, marking and traceability for supplied laminations.

Practical applications and users

IEC 60740-1 is essential for:

• Transformer and inductor designers - to select lamination types, predict core losses and dimension cores accurately.
• Magnetic material and lamination manufacturers - for production tolerances, punching/hole specifications, coating/insulation and welding test criteria.
• Test laboratories and QA teams - to apply standardized electrical and mechanical test procedures and report specific power loss and apparent power values.
• Procurement and compliance - to specify acceptable lamination materials, dimensions and performance in supply contracts.

Practical uses include core design optimization, loss budgeting, supplier qualification, manufacturing quality control, and performance verification of transformer/inductor cores.

Related standards

• IEC 60404-8-4, IEC 60404-8-7 - referenced for magnetic material specifications used in laminations.
• Other IEC magnetic-material test standards and material tables cited within IEC 60740-1.

This standard is a core reference when specifying or validating lamination materials and shapes for reliable, low-loss transformer and inductor cores.

Standards Content (Sample)

INTERNATIONAL IEC
STANDARD 60740-1
First edition
2005-08
Laminations for transformers and inductors –
Part 1:
Mechanical and electrical characteristics

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INTERNATIONAL IEC
STANDARD 60740-1
First edition
2005-08
Laminations for transformers and inductors –
Part 1:
Mechanical and electrical characteristics
 IEC 2005  Copyright - all rights reserved
No part of this publication may be reproduced or utilized in any form or by any means, electronic or
mechanical, including photocopying and microfilm, without permission in writing from the publisher.
International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland
Telephone: [phone] Telefax: [phone] E-mail: [e-mail] Web: www.iec.ch
PRICE CODE
Commission Electrotechnique Internationale XA
International Electrotechnical Commission
МеждународнаяЭлектротехническаяКомиссия
For price, see current catalogue

– 2 – 60740­1 ¤ IEC:2005(E)
CONTENTS
FOREWORD .6
1 Scope .8
2 Normative references.8
3 Terms, definitions and symbols .9
4 Materials and lamination thicknesses. 13
4.1 Materials. 13
4.2 Nominal lamination thickness . 13
4.3 Minimum stacking factor . 14
5 Designation of laminations and lamination strips . 14
5.1 Specified complete shapes. 14
5.2 Lamination strips for specified shapes. 15
5.3 Lamination strips for non­specified laminations. 16
6 Packing and marking. 16
7 Electrical tests. 16
7.1 General . 16
7.2 Core constants . 16
7.3 Magnetic path length . 17
7.4 Core cross­section. 17
8 General conditions for electrical measurements . 18
8.1 Atmospheric conditions . 18
8.2 Test coils . 18
8.3 Test cores. 18
8.4 Harmonic content of the voltage . 18
9 Measurements at high field strength . 18
9.1 General . 18
9.2 Measurement of power loss. 19
9.3 Measurement of total apparent power . 21
10 Measurements at low and medium field strength . 22
10.1 General . 22
10.2 Measurement of amplitude permeability . 22
11 Preferred ranges of laminations . 23
12 Dimensions and tolerances . 24
12.1 Dimensions . 24
12.2 Tolerances. 24
12.3 Symmetry tolerances . 25
13 Dimensions and effective parameters. 25
13.1 General . 25
13.2 Lamination strips Type YS. 25
13.3 Laminations Type YEI 1 . 26
13.4 Laminations Type YUI 1 . 27
13.5 Lamination Types YUI 2 . 30
13.6 Lamination Types YEx 2, YEE 2 and YEI 2. 32
13.7 Lamination Types YEE 2­.L . 33
13.8 Lamination Types YEx 3, YEE 3, YEF 3, YEI 3 and YEL 3. 35

60740­1 ¤ IEC:2005(E) – 3 –
13.9 Lamination Types YEx 4, YEE 4 and YEF 4. 36
13.10Laminations Type YM 1. 38
14 Electrical characteristics for materials . 39
15 Specific total apparent power for laminations . 40
16 Specific power loss for laminations. 41
17 Mechanical characteristics for laminations . 42
17.1 General appearance and conditions . 42
17.2 Cut and punch edge. 42
17.3 Camber. 43
17.4 Distortion . 43
17.5 Bending . 43
17.6 Insulation. 43
17.7 Welding . 44
Annex A (informative)    Conversion of polarisation and field strength into specific
total apparent power . 45
A.1 Specific total apparent power from polarisation and field strength. 45
A.2 Equations for the curves of the magnetic materials. 49
A.3 Constants for non­oriented silicon steel C 21 . 50
A.4 Specific reactive power and specific power loss for non­oriented silicon steel
C 21. 52
A.5 Constants for grain­oriented silicon steel C 22 . 54
A.6 Specific reactive power and specific power loss for grain­oriented silicon steel
C 22. 56
A.7 Influence of the shape on the electrical characteristics for grain­oriented silicon steel
C 22 .58
Bibliography . 59
Figure 1 – Measurements at high field strength, direct and indirect method,    single­
phase cores. 20
Figure 2 – Measurements at high field strength, direct method, three­phase cores. 21
Figure 3 – Measurements at low and medium field strength . 23
Figure 4 – Lamination strips Type YS, dimensions and tolerances. 25
Figure 5 – Laminations Type YEI 1, dimensions . 26
Figure 6 – Laminations Type YUI 1, dimensions. 28
Figure 7 – Layer plan for the lamination strip shapes Type YSUI 1 . 29
Figure 8 – Laminations Type YUI 2, dimensions. 30
Figure 9 – Layer plan for the lamination strip shapes Type YSUI 2 . 32
Figure 10 – Laminations Type YEx 2, dimensions. 32
Figure 11 – Laminations Type YEE 2­.L, using two long E parts, dimensions. 34
Figure 12 – Laminations Type YEx 3, dimensions. 35
Figure 13 – Laminations Type YEx 4, dimensions. 36
Figure 14 – Laminations Type YM 1, dimensions. 38
Figure 15 – Definition and limit of camber . 43
Figure 16 – Definition and limit of distortion. 43
Figure 17 – Definition and limit of bending. 43

– 4 – 60740­1 ¤ IEC:2005(E)
Figure A.1 – Specific total apparent power for non­oriented silicon steel C 21 . 48
Table 1 – Preferred magnetic steel and alloys used for laminations. 13
Table 2 – Material and lamination thickness. 13
Table 3 – Tolerance of the thickness of laminations . 14
Table 4 – Lamination thickness and stacking factor . 14
Table 5 – Test conditions for the materials C 21, C 22 and F 1 for power loss and
total apparent power . 19
Table 6 – Conditions for the measurement of amplitude permeability of cores using
laminations of silicon steel . 22
Table 7 – Conditions for the measurement of amplitude permeability of cores using
laminations of nickel­iron alloys . 23
Table 8 – Summary of preferred shapes . 24
Table 9 – Tolerance according to ISO 286­1 . 24
Table 10 – Tolerances for lamination strips. 25
Table 11 – Laminations Type YEI 1, relation factor    of dimensions and tolerances . 27
Table 12 – Laminations Type YEI 1, diameter of the holes and tolerance factor x. 27
Table 13 – Laminations Type YUI 1, relation of dimensions and tolerances. 28
Table 14 – Laminations Type YUI 1, diameter of the holes and tolerance factor x. 29
Table 15 – Laminations Type YUI 2, relation of dimensions and tolerances. 31
Table 16 – Laminations Type YUI 2, diameter of the holes and tolerance factor x. 31
Table 17 – Laminations Type YEx 2, dimensions and tolerances . 33
Table 18 – Laminations Type YEx 2, effective parameters. 33
Table 19 – Laminations Type YEE 2­.L, using two long E parts,    dimensions and
tolerances . 34
Table 20 – Laminations Type YEE 2­.L,    using two long E parts effective
parameters. 35
Table 21 – Laminations Type YEx 3, dimensions and tolerances . 35
Table 22 – Laminations Type YEx 3, effective parameters. 36
Table 23 – Laminations Type YEE 4, dimensions and tolerances. 37
Table 24 – Laminations Type YEF 4, dimensions and tolerances. 37
Table 25 – Laminations Type YEx 4, effective parameters. 37
Table 26 – Laminations Type YM 1, dimensions and tolerances . 38
Table 27 – Laminations Type YM 1, effective parameters . 39
Table 28 – Materials from IEC 60404­8­4 and IEC 60404­8­7 and Table 1.
Characteristics for the electrical steel sheet and strips, and laminations for the
specific total apparent power p  and the specific power loss p . 40
S0 Fe0
Table 29 – Specific total apparent power p in VA/kg for the materials    from Table 1
S
for all types of laminations and limb width . 41
Table 30 – Specific power loss p  in W/kg for the materials from Table 1 for all
Fe
types of laminations and limb width. 42
Table 31 – Insulation resistance of coated surface of    laminations made from
material according to Table 1. 44
Table 32 – Approximate values for the test of welding for laminations from materials
C 21 and C 22 . 44
Table A.1 – Data for the specific total apparent power and the specific power loss for
C 21 and C 22 materials. 47

60740­1 ¤ IEC:2005(E) – 5 –
Table A.2 – Constants for the specific reactive power    of non­oriented silicon steel
C 21. 50
Table A.3 – Constants for the specific power loss    of non­oriented silicon steel C 21. . 51
Table A.4 – Specific reactive power for non­oriented silicon steel C 21. 52
Table A.5 – Specific power loss for non­oriented silicon steel C 21. 53
Table A.6 – Constants for the specific reactive power of grain­oriented silicon
steel C 22. 54
Table A.7 – Constants for the specific power loss of grain­oriented silicon steel C 22 . 55
Table A.8 – Specific reactive power for grain­oriented silicon steel C 22. 56
Table A.9 – Specific power loss for grain­oriented silicon steel C22. 57
Table A.10 – Parts of the magnetic path in rolling direction l  / l and
W Fe
perpendicular to the rolling direction l  / l  for laminations of 13.3 to 13.10 . 58
q Fe
– 6 – 60740­1 ¤ IEC:2005(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
LAMINATIONS FOR TRANSFORMERS AND INDUCTORS –
Part 1: Mechanical and electrical characteristics
FOREWORD
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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.
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patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International  Standard  IEC 60740­1  has  been  prepared  by  IEC technical  committee  51:
Magnetic components and ferrite materials.
IEC  60740­1  cancels  and  replaces  IEC  60740  published  in  1982  and  its amendment 1
(1991). The main changes are listed below:
a)  ranges with lamination strips YS, YSUI 1, YSUI 2 and laminations YEE 2­.L added;
b)  range YEI 1 extended at the above end;
c)  ranges YED 2, YEF 2, YEL 2, YES 2, Type YM 1­5a and YM 1­7a cancelled;
d)  national designations cancelled;
e)  electrical characteristics for the laminations specified;
f)  mechanical characteristics for laminations added;
g)  holes added for lamination types YEI 1, YUI 1, YUI 2, YM 1;
h)  in Annex A, a conversion of the polarisation ƴ and the field strength ƨ in a specific total
apparent power is defined. For the characteristics of the reactive power and the power
loss, equations and constants are specified.

60740­1 ¤ IEC:2005(E) – 7 –
The text of this standard is based on the following documents:
FDIS Report on voting
51/823/FDIS 51/836/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.
IEC 60740  consists  of  the  following  parts  under  the  general  title Laminations  for
transformers and inductors:
Part 1:  Mechanical and electrical characteristics
Part 2:  Specification for the minimum permeabilities of laminations made of soft magnetic
metallic materials.
The committee has decided that the contents of this publication 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.
A bilingual version of this publication may be issued at a later date.

– 8 – 60740­1 ¤ IEC:2005(E)
LAMINATIONS FOR TRANSFORMERS AND INDUCTORS –
Part 1: Mechanical and electrical characteristics
1  Scope
This part of IEC 60740 specifies the characteristics of laminations. Their preferred use is
cores for  transformers and inductors.  The laminations are  made of sheets and strips of
magnetic materials, specified in IEC 60404­8­4 and IEC 60404­8­7.
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 60050­221,  International  Electrotechnical  Vocabulary  (IEV)  –  Chapter  221:  Magnetic
materials and components
IEC 60404­1:2000, Magnetic materials – Part 1: Classification
IEC 60404­8­4:1998, Magnetic materials – Part 8­4: Specifications for individual materials –
Cold­rolled non­oriented electrical steel sheet and strip delivered in the fully­processed state
IEC 60404­8­7:1998, Magnetic materials – Part 8­7: Specifications for individual materials –
Cold­rolled grain­oriented electrical steel sheet and strip  delivered in the fully­processed
state
IEC 60404­11:1999, Magnetic materials – Part 11: Method of test for the determination of
surface insulation resistance of magnetic sheet and strip
IEC 61021­1:1990, Laminated  core  packages  for  transformers  and  inductors  used  in
telecommunication and electronic equipment – Part 1: Dimensions
IEC 61021­2:1995, Laminated  core  packages  for  transformers  and  inductors  used  in
telecommunication  and  electronic equipment – Part 2: Electrical characteristics for cores
using YEE 2 laminations
ISO 286­1:1988, ISO system of limits and fits – Part 1: Bases of tolerances, deviations and
fits
60740­1 ¤ IEC:2005(E) – 9 –
3  Terms, definitions and symbols
For the purposes of this document, the definitions of IEC 60050­221 and the following apply.
3.1
lamination
produced from a magnetic alloy sheet, usually consisting of one piece or several joined
pieces, forming one complete layer of a laminated core
3.2
lamination strip
produced from a magnetic alloy sheet, which can be composed to a layer of laminations or
stacks for limbs or yokes
3.3
square stack
results, if the height of the package h  is equal to the limb width d.
p
3.4
specific power loss
loss of the core in an alternating field with specified frequency and sinusoidal waveform,
generating a specified flux density divided by the core mass:
P
Fe
p (1)
Fe
m
Fe
where
p   is the specific power loss, in W/kg;
Fe
P is the power loss, in W;
Fe
m   is the core mass, in kg.
Fe
NOTE 1  In the power loss both    the hysteresis loss and eddy current loss are included.
NOTE 2  This is valid for cores with and without an air gap in the magnetic path.
3.5
specific reactive power
reactive  power  of the core in an alternating field by specified frequency and sinusoidal,
specified flux density divided by the core mass:
P
BFe
p (2)
BFe
m
Fe
where
p   is the specific reactive power, in VA/kg;
BFe
P   is the reactive power, in VA;
BFe
m   is the core mass, in kg.
Fe
– 10 – 60740­1 ¤ IEC:2005(E)
3.6
specific reactive power of the air gap
in an alternating field and sinusoidal, specified flux density is the r.m.s. reactive power in
the air gap, divided by the core mass:
ˆ
l˜˜fB
L
p ˜0,25 (3)
BL
l˜U
Fe
where
p is the specific reactive power of the air gap, in VA/kg;
BL
ˆ
B is the peak flux density, in T;
f is the frequency, in Hz;
U is the density of the core, in kg/dm ;
l   Is the length of the air gap, in µm;
L
l   is the path length, in cm.
Fe
3.7
specific total apparent power of cores without air gap
in the mean flux path, the specific total apparent power consists of the specific reactive
power and the specific power loss of the core and is the product of sinusoidal voltage and
r.m.s. current divided by the core mass:
2 2
p p  p (4)
S
BFe Fe
UI˜ P
S
p (5)
S
mm
Fe Fe
where
P is the total apparent power, in VA;
S
p is the specific total apparent power, in VA/kg;
S
p   is the specific reactive power, in VA/kg;
BFe
p is the specific power loss, in W/kg;
Fe
U is the voltage, in V;
I is the r.m.s. current, in A;
m is the core mass, in kg.
Fe
3.8
specific total apparent power of cores with air gap
in the mean flux path, the specific total apparent power consists of the specific reactive
power of the core, the specific reactive power of the air gap and the specific power loss:
2 2
P p  p   p (6)
S BFe BL
Fe
60740­1 ¤ IEC:2005(E) – 11 –
where
p is the specific total apparent power, in VA/kg;
S
p   is the specific reactive power of the core, in VA/kg;
BFe
p   is the specific reactive power of the air gap, in VA/kg;
BL
p is the specific power loss, in W/kg.
Fe
3.9
magnetic path length
arithmetic mean of the longest and the shortest path length of the core neglecting radii.
NOTE For details of the calculation for each core, see 13.3 to 13.10.
3.10  Symbols
A core cross­section, in mm ;
Fe
ˆ
B peak flux density, in T;
ˆ
B nominal peak flux density, in T;
n
ˆ
B peak flux density for the characteristic of the specific reactive power, in dT;
–1
C core constant 1, in mm ;
–3
C core constant 2, in mm ;
c , c constants for the characteristic of the specific reactive power;
1 2
c , c constants for the characteristic of the specific power loss;
3 4
d limb width, in mm;
f frequency, in Hz;
ˆ
H peak field strength, in A/m;
h stack height, in mm;
p
I current, in A;
I , I , I currents in the phases of three­phase cores, in A;
1 2 3
ˆ
J peak polarisation, in T;
l magnetic path length, in mm;
l magnetic path length, in mm;
Fe
l l magnetic path lengths for three­phase cores, in mm;
Fe1, Fe2
l path length of the air gap, in µm;
L
l magnetic path length cross to the rolling direction, in mm;
q
l magnetic path length in rolling direction, in mm;
w
m core mass, in kg;
Fe
N number of turns;
N number of turns of winding N ;
1 1
N number of turns of winding N ;
2 2
P , P , P power loss in the phases of three­phase cores, in W;
1 2 3
P reactive power of the core, in VA;
BFe
P reactive power of the air gap, in VA;
BL
P power loss, in W;
Fe
– 12 – 60740­1 ¤ IEC:2005(E)
P test value of the power loss, in W;
m
P total apparent power, in VA;
S
p specific reactive power, in VA/kg;
B
p specific reactive power of the core, in VA/kg;
BFe
p specific reactive power of the air gap, in VA/kg;
BL
p specific power loss; in W/kg;
Fe
p cardinal value for the specific power loss, in W/kg;
Fe0
p specific total apparent power, in VA/kg;
S
p cardinal value of the total apparent power, in VA/kg;
S0
p specific total apparent power at sinusoidal current; in VA/kg;
S, sin
R resistance of winding N , in :;
1 1
R resistance of winding N , in :;
2 2
R precision resistor, in :;
n
R resistance of the voltmeter, in :;
V
R resistance of the voltage path of the wattmeter, in :;
W
U voltage, in V;
U voltage of the source, in V;
U voltage of the winding N , in V;
2 r.m.s 2
U voltage of the winding N , in V;
2 avg 2
ˆ
U peak value of the voltage across R , in V;
n n
V core volume, in mm ;
Fe
x tolerance factor;
y auxiliary value for the characteristics of the specific reactive power;
y , y constants for the characteristics of the specific reactive power;
1 2
y constant for the characteristics of the specific power loss;
K stacking factor;
–9
µ magnetic constant, in H/cm (4 · S · 10  H/cm);
µ amplitude permeability;
a
µ initial permeability;
i
S in this standard = 3,1416;
U the density of the core alloy, in kg/dm .

60740­1 ¤ IEC:2005(E) – 13 –
4  Materials and lamination thicknesses
4.1  Materials
Laminations are made from one of the materials specified in Table 1.
Table 1 – Preferred magnetic steel and alloys used for laminations
Designation
Approximate
Density
Material composition in IEC 60404­8­4
kg/dm IEC 60404­1
addition to iron
IEC 60404­8­7
M 270­35A 5
7,65 M 330­35A 5
M 330­50A 5
Non­oriented
1 % to 3 % silicon C 21
silicon steel
M 400­50A 5
7,7
M 530­50A 5
7,8 M 800­50A 5
Grain­oriented
3,2 % silicon 7,65 C 22 M 165­35S 5
silicon steel
72 % to 83 % nickel 8,7 E 1
45 % to 50 % nickel
Nickel­iron
(both oriented and non­ 8,25 E 3
alloys
____
oriented)
35 % to 40 % nickel 8,15 E 4
Cobalt­iron 47 % to 50 % cobalt
F 1
alloys (isotropic)
4.2  Nominal lamination thickness
Lamination  thickness  shall  be  selected  from  one  of  the  values  specified  in  Table  2,
according to the material in use.
Table 2 – Material and lamination thickness
Thickness
Material designation
mm
0,5  0,38  0,35  0,3 0,2 0,1  0,05
C 21 o ­ o ­ ­ ­ ­
C 22 ­ ­ o ­ ­ ­ ­
E 1 ­ x x o o o x
E 3 non­oriented ­ x x o o o x
E 3 grain­oriented ­ ­ ­ ­ ­ o x
E 4 ­ x x o o o x
F 1 ­ ­ x o o o x
NOTE  o: preferred value, x: usual, ­: not usual.

– 14 – 60740­1 ¤ IEC:2005(E)
The allowed tolerance of the thickness of the laminations in Table 3 is corresponding to the
appropriate value taken from IEC 60404­8­4 and IEC 60404­8­7.
Table 3 – Tolerance of the thickness of laminations
Tolerances
Material designation mm
Thickness 0,5 mm Thickness 0,35 mm
C 21 ± 0,04 ± 0,028
C 22 ­ ± 0,03
4.3  Minimum stacking factor
The minimum stacking factor K for usual materials and thickness shall be not lower than the
values shown in Table 4. They are valid for uniform stacks with a minimum height of 10 mm
subjected to a uniform pressure of 15 kN/m  perpendicular to the lamination.
Table 4 – Lamination thickness and stacking factor
Minimum stacking factor K
Lamination
Non­oriented Grain oriented Nickel­iron and
thickness
silicon steel silicon steel cobalt­iron alloys
mm
C 21 C 22 E, F
0,5 0,95 – –
0,35 0,94 0,95 0,94
0,30 – – 0,92
0,20 ­ – 0,9
0,10 0,9 0,9 0,85
0,05 ­ 0,88 0,8
5  Designation of laminations and lamination strips
The designation contains all information needed to describe the laminations sufficiently and
unmistakably.
5.1  Specified complete shapes
5.1.1  Lamination outline shapes
LAM IEC 60740­1 YUI 1­50 H M 530­50A 5
Lamination
Number of this specification
Sign, that this designation is different from
eventual used national designations
Shape and size according to 13.3 to 13.10
Sign for holes, H with holes, X without holes
Material in accordance with Table 1
IEC   1195/05
60740­1 ¤ IEC:2005(E) – 15 –
5.1.2  Specified shape with lamination strips
LAM IEC 60740­1 YSUI 1­50 X M 165­35S 5
Lamination
Number of this standard
Sign, that this designation is different from eventual
used national designations
Sign, that the shape is made of lamination strips
Shape and size according to 13.4.2 or 13.5.2
Sign for holes, H with holes, X without holes
Material in accordance with Table 1
IEC   1196/05
5.2  Lamination strips for specified shapes
5.2.1  Lamination strips for yokes
LAM IEC 60740­1 YSUI 1­50 Y X M 165­35S 5
Lamination
Number of this standard
Sign, that this designation is different from eventual
used national designations
Sign, that the shape is made of lamination strips
Shape and size according to 13.4.2 or 13.5.2
Sign for lamination strips for yokes
Sign for holes, H with holes, X without holes
Material in accordance with Table 1
IEC   1197/05
5.2.2  Lamination strips for limbs
LAM IEC 60740­1 YSUI 1­50 L X M 165­35S 5
Lamination
Number of this standard
Sign, that this designation is different from eventual
used national designations
Sign, that the shape is made of lamination strips
Shape and size according to 13.4.2 or 13.5.2
Sign for lamination strips for limbs
Sign for holes, H with holes, X without holes
Material in accordance with Table 1
IEC   1198/05
– 16 – 60740­1 ¤ IEC:2005(E)
5.3 Lamination strips for non­specified laminations
LAM IEC 60740­1 YS100 u 500 X M 165­35S 5
Lamination
Number of this standard
Sign, that this designation is different from eventual
used national designations
Lamination strips according to 13.2
Width of the lamination strip in mm
Length of the lamination strip in mm
Sign for holes, H with holes, X without holes
Material in accordance with Table 1
IEC   1199/05
6  Packing and marking
The laminations shall be packed for transit in such a manner that no deterioration will occur.
Unless otherwise specified, all parts designing a layer of lamination shall be packed in one
packaging unit.
All packages shall be marked with the following information:
–  lamination designation;
–  quantity by mass or by number;
–  the manufacturer’s lot identification or date of manufacture;
–  manufacturer.
Example of marking:
–  lamination: LAM IEC 60740­1 YEI 1­40 H M 330­35A 5
–  quantity:
–  date of manufacture:
–  manufacturer:
7  Electrical tests
7.1  General
Electrical tests for stacked laminations shall be carried out for the appropriate materials
specified  in  Table 1  according  to  the  test  parameters  specified  in  Tables  5,  6  and  7.
Effective parameters see 7.2 to 7.4.
7.2  Core constants
The core constants of laminations are calculated as follows:
l
Fe
C (7)
A
Fe
l
Fe
C (8)
A
Fe
60740­1 ¤ IEC:2005(E) – 17 –
where
–1
C is the core constant 1, in mm ;
–3;
C   is the core constant 2, in mm
l is the magnetic path length, in mm, calculated as in 7.3;
Fe
A   is the core cross­section, in mm , taking into account the stacking factorȘ̣, see 7.4.
Fe
Further, the core volume, in mm , and the core mass, in kg, are calculated as follows:
V = l  · A (9)
Fe Fe Fe
m  = V · ȡ (10)
Fe Fe
whereȡ is the density of the alloy, in kg/dm .
The effective parameters of laminated cores with square cross­section and a stacking factor
of  0,95  are  shown  in  Tables  17,  18,  19,  20,  21,  22,  23,  24,  25,  26  and  27.  For  the
laminations  in  13.3,  13.4.1  and  13.5.1  the  equations  for  the  core  constants  are  given
subsequent to the associated tables.
7.3  Magnetic path length
The magnetic path length l  is calculated as the arithmetic mean of the longest and the
Fe
shortest path length of the core neglecting radii.
NOTE  For details on the calculation for each core, see 13.3, 13.4.1 and 13.5.1.
7.4  Core cross­section
The core cross­section is calculated as the product of (centre) limb width, stack height and
stacking factor:
A = d · h · Ș (11)
Fe p
where
A is the core cross­section, in mm ;
Fe
d is the limb width, in mm;
h is the stack height, in mm;
p
K is the stacking factor.
For cores with square stack (h = d) shown in Tables 17, 18, 19, 20, 21, 22, 23, 24, 25, 26
p
and 27 and withȘ = 0,95, the core cross­section is:
A  = 0,95 · d (12)
Fe
For other stack heights and stacking factors differing from Table 4, the values for A  and
Fe
C shall be corrected by multiplying with the following factors:
h ˜K
p
The factor for A  is:
Fe
d˜ 0,95
d˜ 0,95
The factor for C is:
h ˜K
p
– 18 – 60740­1 ¤ IEC:2005(E)
NOTE Alternatively, for a given core stack, the core cross­section may be determined as follows:
m
Fe
For YEI, YEx, YUI and YM: A (13)
Fe
l ˜U
Fe
8  General conditions for electrical measurements
8.1  Atmospheric conditions
Unless otherwise stated, all tests shall be carried out at room temperature.
8.2  Test coils
The electrical tests in Clauses 15 and 16 are valid for the square stack. The stack height of
the test coil and of the core may be changed, if the values are not changed. However, the
test coils shall be suitable to the stack of laminations to be tested. The voltage winding N
shall be the inner winding and be as close as possible to the core, and its resistance R
shall be small compared to the resistance of its load.
The resistance in the supply circuit, including the coil resistance R  and the resistance of
the current measuring device (current meter, current amplifier or precision resistor), shall
be small, so that they do not result in any appreciable distortion of the voltage.
8.3  Test cores
The laminations shall physically be in accordance with the requirements of Clauses 4 and
13  and  shall  be  selected  at  random  from  those  which  are  fully  processed  for  the  end
application. They shall be interleaved as a stack and shall consist of equal numbers of all
necessary parts designing a complete layer of lamination.
NOTE Using grain­oriented and non­oriented silicon steel the laminations may be interleaved equilateral. Only in
case of arbitration they shall be interleaved one by one throughout the stack.
Test cores made of lamination strips are  a matter  of agreement between customer  and
manufacturer.
8.4  Harmonic content of the voltage
In  order  to  obtain  comparable  results,  sinusoidal  flux  density  shall  be  used  for  the
measurements.  During  the  test,  the harmonic  content shall not exceed  6 %. Where  two
voltmeters V and V  in Figure 1a are connected in parallel to the winding N , the first one
1 2 2
is measuring the r.m.s. value and the second one is measuring the average value. The form
factor shall be calculated from the ratio of the r.m.s. value to the average value. If this form
factor is between 1,10 and 1,12 and at the same time the wave­shape as observed on the
oscilloscope  does  not  show  obvious  distortion,  the  harmonic  content  of  the  secondary
voltage across the winding N  and hence of the flux density will be sufficiently small.
9  Measurements at high field strength
9.1  General
One of the circuits of Figure 1a, Figure 1b or Figure 2 shall be used. The test conditions
shall  be  in  accordance with the values specified in Table 5. Test certificates for lots of
delivery are a matter of agreement between customer and manufacturer.

60740­1 ¤ IEC:2005(E) – 19 –
Table 5 – Test conditions for the materials C 21, C 22 and F 1 for power loss
and total apparent power
Material designation Thickness Frequency Peak flux density
mm Hz T
0,35 and 0,5 50 or 60 1,5
Non­oriented silicon steel
C 21
0,1 400 1,0
0,35 50 or 60 1,7
Grain­oriented silicon steel
C 22
0,1 and 0,15 400 1,0
0,2 and 0,35 50 or 60 2,0
Cobalt­iron alloys
F 1
0,1 400 1,7
For the following equations the following symbols are used:
U is the voltage on winding N , in V;
2 2
f is the frequency, in Hz;
ˆ
B is the peak flux density, in T;
A is the core cross­section, in mm (see 7.4);
Fe
I is the current, in A;
I , I , I   currents in the phases of three­phase cores, in A;
1 2 3
m is the core mass, in kg;
Fe
N is the number of turns of the winding N ;
1 1
N is the number of turns of the winding N ;
2 2
P is the power loss, in W;
Fe
P is the test value of power loss, in W;
m
P is the total apparent power, in VA;
S
P , P , P is the power loss in the phases of three­phase cores, in W;
1 2 3
R is the resistance of the winding N , in :;
2 2
R is the resistance of the voltmeter V , in :;
V 2
R is the resistance of the voltage winding of the wattmeter, in :.
W
9.2  Measurement of power loss
9.2.1  Power loss for single­phase cores
Where the circuit of Figure 1a is used, both switches are closed for the determination of the
form factor (see 8.4). Switch S  is then opened and the source voltage U  is adjusted so
1 1
that the reading of the secondary voltage U  on the average sensing voltmeter V  has the
2 2
value calculated from the following equation:
21˜˜Sf
ˆ
U = ˜A˜BN˜˜ (14)
2 Fe 2
§·
2 11
1R˜
¨¸
RR
©¹VW
With switch S open and switch S  closed, the wattmeter is read. Neglecting the copper
1 2
losses  in  winding  N   and  in  the  ammeter,  the  power  loss P   are  calculated  with  the
1 Fe
following equation from the measured power loss P :
m
– 20 – 60740­1 ¤ IEC:2005(E)
ª §·ºªº§·
N 1 1 11
P  =P˜ UR˜ ˜1 ˜ (15)
« ¨¸»«»¨¸
m22
Fe
N RR RR
«2 ©¹VW»«»©¹VW
¬ ¼¬¼
P
Fe
NOTE 1 The result of the measurement is often expressed in terms of specific power loss p , in W/kg.
Fe
m
Fe
Wher
...

IEC 60740-1 ®
Edition 1.0 2005-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Laminations for transformers and inductors –
Part 1: Mechanical and electrical characteristics

Tôles découpées pour transformateurs et inductances –
Partie 1: Caractéristiques électriques et mécaniques

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IEC 60740-1 ®
Edition 1.0 2005-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Laminations for transformers and inductors –
Part 1: Mechanical and electrical characteristics

Tôles découpées pour transformateurs et inductances –
Partie 1: Caractéristiques électriques et mécaniques

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX XA
ICS 29.100.10 ISBN 978-2-88912-783-2

– 2 – 60740-1  IEC:2005
CONTENTS
FOREWORD . 6
1 Scope . 8
2 Normative references . 8
3 Terms, definitions and sy mbols . 9
4 Materials and lamination thickn es s e s . 13
4.1 Materials . 13
4.2 Nominal lamination thickness . 13
4.3 Minimum stacking factor . 14
5 Designation of laminations and lamination strips . 14
5.1 Specified complete shapes . 14
5.2 Lamination strips for specified shapes . 15
5.3 Lamination strips for non-specified laminations . 16
6 Packing and marking . 16
7 Electrical tests . 16
7.1 General . 16
7.2 Core constants . 16
7.3 Magnetic path length . 17
7.4 Core cross-section . 17
8 General conditions for electrical measurements . 18
8.1 Atmospheric conditions . 18
8.2 Test coils . 18
8.3 Test cores . 18
8.4 Harmonic content of the voltage . 18
9 Measurements at high field strength . 18
9.1 General . 18
9.2 Measurement of power loss . 19
9.3 Measurement of total apparent power . 21
10 Measurements at low and medium field strength . 22
10.1 General . 22
10.2 Measurement of amplitude permeability . 22
11 Preferred ranges of laminations . 23
12 Dimensions and tolerances . 24
12.1 Dimensions . 24
12.2 Tolerances . 24
12.3 Symmetry tolerances . 25
13 Dimensions and effective parameters . 25
13.1 General . 25
13.2 Lamination strips Type YS . 25
13.3 Laminations Type YEI 1 . 26
13.4 Laminations Type YUI 1 . 27
13.5 Lamination Types YUI 2 . 30
13.6 Lamination Types YEx 2, YEE 2 and YEI 2 . 32
13.7 Lamination Types YEE 2-.L . 33
13.8 Lamination Types YEx 3, YEE 3, YEF 3, YEI 3 and YEL 3 . 35

60740-1  IEC:2005 – 3 –
13.9 Lamination Types YEx 4, YEE 4 and YEF 4 . 36
13.10 Laminations Type YM 1 . 38
14 Electrical characteristics for mate rials . 39
15 Specific total apparent power for laminations . 40
16 Specific power loss for laminations . 41
17 Mechanical characteristics for laminations . 42
17.1 General appearance and conditi ons . 42
17.2 Cut and punch edge . 42
17.3 Camber . 43
17.4 Distortion . 43
17.5 Bending . 43
17.6 Insulation . 43
17.7 Weldin g . 44

Annex A (informative) Conversion of polarisation and field strength into specific total
apparent power . . 45
A.1 Specific total apparent power from polarisation and field strength . 45
A.2 Equations for the curves of the magnetic materials . 49
A.3 Constants for non-oriented silicon steel C 21 . 50
A.4 Specific reactive power and specific power loss for non-oriented silicon steel C 21 . 52
A.5 Constants for grain-oriented silicon steel C 22 . 54
A.6 Specific reactive power and specific power loss for grain-oriented silicon steel

C 22 . . 56
A.7 Influence of the shape on the electrical characteristics for grain-oriented silicon steel C 22 . 58

Bibliography . . 59

Figure 1 – Measurements at high field strength, direct and indirect method, single-
phase cores . 20
Figure 2 – Measurements at high field strength, direct method, three-phase cores . 21
Figure 3 – Measurements at low and medium field strength . 23
Figure 4 – Lamination strips Type YS, dimensions and tolerances . 25
Figure 5 – Laminations Type YEI 1, dimensions . 26
Figure 6 – Laminations Type YUI 1, dimensions . 28
Figure 7 – Layer plan for the lamination strip shapes Type YSUI 1 . 29
Figure 8 – Laminations Type YUI 2, dimensions . 30
Figure 9 – Layer plan for the lamination strip shapes Type YSUI 2 . 32
Figure 10 – Laminations Type YEx 2, dimensi ons . 32
Figure 11 – Laminations Type YEE 2-.L, using two long E parts, dimensions . 34
Figure 12 – Laminations Type YEx 3, dimensi ons . 35
Figure 13 – Laminations Type YEx 4, dimensi ons . 36
Figure 14 – Laminations Type YM 1, dime ns ions . 38
Figure 15 – Definition and limit of camber . 43
Figure 16 – Definition and limit of distortion . 43
Figure 17 – Definition and limit of bending . 43
Figure A.1 – Specific total apparent power for non-oriented silicon steel C 21 . 48

– 4 – 60740-1  IEC:2005
Table 1 – Preferred magnetic steel and alloys used for laminations . 13
Table 2 – Material and lamination thickness . 13
Table 3 – Tolerance of the thickness of laminations . 14
Table 4 – Lamination thickness and stacking factor . 14
Table 5 – Test conditions for the materials C 21, C 22 and F 1 for power loss and total

apparent power . . 19
Table 6 – Conditions for the measurement of amplitude permeability of cores using
laminations of silicon steel . 22
Table 7 – Conditions for the measurement of amplitude permeability of cores using
laminations of nickel-iron alloys . 23
Table 8 – Summary of preferred shapes . 24
Table 9 – Tolerance according to ISO 286-1 . 24
Table 10 – Tolerances for lamination strips . 25
Table 11 – Laminations Type YEI 1, relation factor of dimensions and tolera nc es . 27
Table 12 – Laminations Type YEI 1, diameter of the holes and tolerance factor x . 27
Table 13 – Laminations Type YUI 1, relation of dimensions and tolerances . 28
Table 14 – Laminations Type YUI 1, diameter of the holes and tolerance factor x . 29
Table 15 – Laminations Type YUI 2, relation of dimensions and tolerances . 31
Table 16 – Laminations Type YUI 2, diameter of the holes and tolerance factor x . 31
Table 17 – Laminations Type YEx 2, dimensions and tolerances . 33
Table 18 – Laminations Type YEx 2, effective parameter s . 33
Table 19 – Laminations Type YEE 2-.L, using two long E parts, dimensions and
tolerances . 34
Table 20 – Laminations Type YEE 2-.L, using two long E parts effective parameters . 35
Table 21 – Laminations Type YEx 3, dimensions and tolerances . 35
Table 22 – Laminations Type YEx 3, effective parameter s . 36
Table 23 – Laminations Type YEE 4, dimensions and toleranc es . 37
Table 24 – Laminations Type YEF 4, dimensions and tolerances . 37
Table 25 – Laminations Type YEx 4, effective parameters . 37
Table 26 – Laminations Type YM 1, dimensions and tolerances . 38
Table 27 – Laminations Type YM 1, effective parameters . 39
Table 28 – Materials from IEC 60404-8-4 and IEC 60404-8-7 and Table 1.
Characteristics for the electrical steel sheet and strips, and laminations for the specific
total apparent power p and the specific power loss p . 40
S0 Fe0
Table 29 – Specific total apparent power p in VA/kg for the materials from Table 1
S
for all types of laminations and limb width . 41
Table 30 – Specific power loss p in W/kg for the materials from Table 1 for all types
Fe
of laminations and limb width . 42
Table 31 – Insulation resistance of coated surface of laminations made from material
according to Table 1 . 44
Table 32 – Approximate values for the test of welding for laminations from materials
C 21 and C 22 . . 44
Table A.1 – Data for the specific total apparent power and the specific power loss for
C 21 and C 22 materials . 47
Table A.2 – Constants for the specific reactive power of non-oriented silicon steel
C 21 . . 50

60740-1  IEC:2005 – 5 –
Table A.3 – Constants for the specific power loss of non-oriented silicon steel C 21. . 51
Table A.4 – Specific reactive power for non-oriented silicon steel C 21. . 52
Table A.5 – Specific power loss for non-oriented silicon steel C 21 . 53
Table A.6 – Constants for the specific reactive power of grain-oriented silicon
steel C 22. . 54
Table A.7 – Constants for the specific power loss of grain-oriented silicon steel C 22 . 55
Table A.8 – Specific reactive power for grain-oriented silicon steel C 22. . 56
Table A.9 – Specific power loss for grain-oriented silicon steel C22. . 57
Table A.10 – Parts of the magnetic path in rolling direction l / l and perpendicular
W Fe
to the rolling direction l / l for laminations of 13.3 to 13.10 . 58
q Fe
– 6 – 60740-1  IEC:2005
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
LAMINATIONS FOR TRANSFORMERS AND INDUCTORS –

Part 1: Mechanical and electrical characteristics

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
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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.
International Standard IEC 60740-1 has been prepared by IEC technical committee 51:
Magnetic components and ferrite materials.
IEC 60740-1 cancels and replaces IEC 60740 published in 1982 and its amendment 1 (1991).
The main changes are listed below:
a) ranges with lamination strips YS, YSUI 1, YSUI 2 and laminations YEE 2-.L added;
b) range YEI 1 extended at the above end;
c) ranges YED 2, YEF 2, YEL 2, YES 2, Type YM 1-5a and YM 1-7a cancelled;
d) national designations cancelled;
e) electrical characteristics for the laminations specified;
f) mechanical characteristics for laminations added;
g) holes added for lamination types YEI 1, YUI 1, YUI 2, YM 1;
h) in Annex A, a conversion of the polarisation Ĵ and the field strength Ĥ in a specific total
apparent power is defined. For the characteristics of the reactive power and the power
loss, equations and constants are specified.

60740-1  IEC:2005 – 7 –
This bilingual version (2011-11) corresponds to the monolingual English version, published in
2005-08.
The text of this standard is based on the following documents:
FDIS Report on voting
51/823/FDIS 51/836/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.
The French version of this standard has not been voted upon.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
IEC 60740 consists of the following parts under the general title Laminations for transformers
and inductors:
Part 1: Mechanical and electrical characteristics
Part 2: Specification for the minimum permeabilities of laminations made of soft magnetic
metallic materials.
The committee has decided that the contents of this publication 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.
– 8 – 60740-1  IEC:2005
LAMINATIONS FOR TRANSFORMERS AND INDUCTORS –

Part 1: Mechanical and electrical characteristics

1 Scope
This part of IEC 60740 specifies the characteristics of laminations. Their preferred use is
cores for transformers and inductors. The laminations are made of sheets and strips of
magnetic materials, specified in IEC 60404-8-4 and IEC 60404-8-7.
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 60050-221, International Electrotechnical Vocabulary (IEV) – Chapter 221: Magnetic
materials and components
IEC 60404-1:2000, Magnetic materials – Part 1: Classification
IEC 60404-8-4:1998, Magnetic materials – Part 8-4: Specifications for individual materials –
Cold-rolled non-oriented electrical steel sheet and strip delivered in the fully-processed state
IEC 60404-8-7:1998, Magnetic materials – Part 8-7: Specifications for individual materials –
Cold-rolled grain-oriented electrical steel sheet and strip delivered in the fully-processed
state
IEC 60404-11:1999, Magnetic materials – Part 11: Method of test for the determination of
surface insulation resistance of magnetic sheet and strip
IEC 61021-1:1990, Laminated core packages for transformers and inductors used in
telecommunication and electronic equipment – Part 1: Dimensions
IEC 61021-2:1995, Laminated core packages for transformers and inductors used in
telecommunication and electronic equipment – Part 2: Electrical characteristics for cores
using YEE 2 laminations
ISO 286-1:1988, ISO system of limits and fits – Part 1: Bases of tolerances, deviations and
fits
60740-1  IEC:2005 – 9 –
3 Terms, definitions and symbols
For the purposes of this document, the definitions of IEC 60050-221 and the following apply.
3.1
lamination
produced from a magnetic alloy sheet, usually consisting of one piece or several joined
pieces, forming one complete layer of a laminated core
3.2
lamination strip
produced from a magnetic alloy sheet, which can be composed to a layer of laminations or
stacks for limbs or yokes
3.3
square stack
results, if the height of the package h is equal to the limb width d.
p
3.4
specific power loss
loss of the core in an alternating field with specified frequency and sinusoidal waveform,
generating a specified flux density divided by the core mass:
P
Fe
p  (1)
Fe
m
Fe
where
p is the specific power loss, in W/kg;
Fe
P is the power loss, in W;
Fe
m is the core mass, in kg.
Fe
NOTE 1 In the power loss both the hysteresis loss and eddy current loss are included.
NOTE 2 This is valid for cores with and without an air gap in the magnetic path.
3.5
specific reactive power
reactive power of the core in an alternating field by specified frequency and sinusoidal,
specified flux density divided by the core mass:
P
BFe
p  (2)
BFe
m
Fe
where
p is the specific reactive power, in VA/kg;
BFe
P is the reactive power, in VA;
BFe
m is the core mass, in kg.
Fe
– 10 – 60740-1  IEC:2005
3.6
specific reactive power of the air gap
in an alternating field and sinusoidal, specified flux density is the r.m.s. reactive power in the
air gap, divided by the core mass:
ˆ
lf B
L
p0,25 (3)
BL
l 
Fe
where
p is the specific reactive power of the air gap, in VA/kg;
BL
ˆ
B is the peak flux density, in T;
f is the frequency, in Hz;
 is the density of the core, in kg/dm ;
l Is the length of the air gap, in µm;
L
l is the path length, in cm.
Fe
3.7
specific total apparent power of cores without air gap
in the mean flux path, the specific total apparent power consists of the specific reactive
power and the specific power loss of the core and is the product of sinusoidal voltage and
r.m.s. current divided by the core mass:
2 2
p  p  p (4)
S
BFe Fe
UI P
S
p (5)
S
mm
Fe Fe
where
P is the total apparent power, in VA;
S
p is the specific total apparent power, in VA/kg;
S
p is the specific reactive power, in VA/kg;
BFe
p is the specific power loss, in W/kg;
Fe
U is the voltage, in V;
I is the r.m.s. current, in A;
m is the core mass, in kg.
Fe
3.8
specific total apparent power of cores with air gap
in the mean flux path, the specific total apparent power consists of the specific reactive
power of the core, the specific reactive power of the air gap and the specific power loss:
2 2
P p  p  p (6)
S BFe BL
Fe
60740-1  IEC:2005 – 11 –
where
is the specific total apparent power, in VA/kg;
p
S
p is the specific reactive power of the core, in VA/kg;
BFe
p is the specific reactive power of the air gap, in VA/kg;
BL
p is the specific power loss, in W/kg.
Fe
3.9
magnetic path length
arithmetic mean of the longest and the shortest path length of the core neglecting radii.
NOTE For details of the calculation for each core, see 13.3 to 13.10.
3.10 Symbols
A core cross-section, in mm ;
Fe
ˆ
B peak flux density, in T;
ˆ
B nominal peak flux density, in T;
n
ˆ
B peak flux density for the characteristic of the specific reactive power, in dT;
–1
C core constant 1, in mm ;
–3
C core constant 2, in mm ;
c , c constants for the characteristic of the specific reactive power;
1 2
c , c constants for the characteristic of the specific power loss;
3 4
d limb width, in mm;
f frequency, in Hz;
ˆ
H peak field strength, in A/m;
h stack height, in mm;
p
I current, in A;
I , I , I currents in the phases of three-phase cores, in A;
1 2 3
ˆ
J peak polarisation, in T;
l magnetic path length, in mm;
l magnetic path length, in mm;
Fe
l l magnetic path lengths for three-phase cores, in mm;
Fe1, Fe2
l path length of the air gap, in µm;
L
l magnetic path length cross to the rolling direction, in mm;
q
l magnetic path length in rolling direction, in mm;
w
m core mass, in kg;
Fe
N number of turns;
N number of turns of winding N ;
1 1
N number of turns of winding N ;
2 2
P , P , P power loss in the phases of three-phase cores, in W;
1 2 3
P reactive power of the core, in VA;
BFe
P reactive power of the air gap, in VA;
BL
P power loss, in W;
Fe
– 12 – 60740-1  IEC:2005
P test value of the power loss, in W;
m
P total apparent power, in VA;
S
p specific reactive power, in VA/kg;
B
p specific reactive power of the core, in VA/kg;
BFe
p specific reactive power of the air gap, in VA/kg;
BL
p specific power loss; in W/kg;
Fe
p cardinal value for the specific power loss, in W/kg;
Fe0
p specific total apparent power, in VA/kg;
S
p cardinal value of the total apparent power, in VA/kg;
S0
p specific total apparent power at sinusoidal current; in VA/kg;
S, sin
R resistance of winding N , in ;
1 1
R resistance of winding N , in ;
2 2
R precision resistor, in ;
n
R resistance of the voltmeter, in ;
V
R resistance of the voltage path of the wattmeter, in ;
W
U voltage, in V;
U voltage of the source, in V;
U voltage of the winding N , in V;
2 r.m.s 2
U voltage of the winding N , in V;
2 avg 2
ˆ
U peak value of the voltage across R , in V;
n n
V core volume, in mm ;
Fe
x tolerance factor;
y auxiliary value for the characteristics of the specific reactive power;
y , y constants for the characteristics of the specific reactive power;
1 2
y constant for the characteristics of the specific power loss;
 stacking factor;
–9
µ magnetic constant, in H/cm (4 ·  · 10 H/cm);
µ amplitude permeability;
a
µ initial permeability;
i
 in this standard = 3,1416;
 the density of the core alloy, in kg/dm .

60740-1  IEC:2005 – 13 –
4 Materials and lamination thicknesses
4.1 Materials
Laminations are made from one of the materials specified in Table 1.
Table 1 – Preferred magnetic steel and alloys used for laminations
Designation
Approximate
Density
Material composition in IEC 60404-8-4
kg/dm IEC 60404-1
addition to iron
IEC 60404-8-7
M 270-35A 5
7,65 M 330-35A 5
M 330-50A 5
Non-oriented
1 % to 3 % silicon C 21
silicon steel
M 400-50A 5
7,7
M 530-50A 5
7,8 M 800-50A 5
Grain-oriented
3,2 % silicon 7,65 C 22 M 165-35S 5
silicon steel
72 % to 83 % nickel 8,7 E 1
45 % to 50 % nickel
Nickel-iron
(both oriented and 8,25 E 3
alloys ____
non-oriented)
35 % to 40 % nickel 8,15 E 4
Cobalt-iron 47 % to 50 % cobalt
F 1
alloys (isotropic)
4.2 Nominal lamination thickness
Lamination thickness shall be selected from one of the values specified in Table 2, according
to the material in use.
Table 2 – Material and lamination thickness
Thickness
Material designation mm
0,5 0,38 0,35 0,3 0,2 0,1 0,05
C 21 o - o - - - -
C 22 - - o - - - -
E 1 - x x o o o x
E 3 non-oriented - x x o o o x
E 3 grain-oriented - - - - - o x
E 4 - x x o o o x
F 1 - - x o o o x
NOTE o: preferred value, x: usual, -: not usual.

– 14 – 60740-1  IEC:2005
The allowed tolerance of the thickness of the laminations in Table 3 is corresponding to the
appropriate value taken from IEC 60404-8-4 and IEC 60404-8-7.
Table 3 – Tolerance of the thickness of laminations
Tolerances
Material designation mm
Thickness 0,5 mm Thickness 0,35 mm
C 21 ± 0,04 ± 0,028
C 22 - ± 0,03
4.3 Minimum stacking factor
The minimum stacking factor  for usual materials and thickness shall be not lower than the
values shown in Table 4. They are valid for uniform stacks with a minimum height of 10 mm
subjected to a uniform pressure of 15 kN/m perpendicular to the lamination.
Table 4 – Lamination thickness and stacking factor
Minimum stacking factor 
Lamination
Non-oriented Grain oriented Nickel-iron and
thickness
silicon steel silicon steel cobalt-iron alloys
mm
C 21 C 22 E, F
0,5 0,95 – –
0,35 0,94 0,95 0,94
0,30 – – 0,92
0,20 - – 0,9
0,10 0,9 0,9 0,85
0,05 - 0,88 0,8
5 Designation of laminations and lamination strips
The designation contains all information needed to describe the laminations sufficiently and
unmistakably.
5.1 Specified complete shapes
5.1.1 Lamination outline shapes

LAM IEC 60740-1 YUI 1-50 H M 530-50A 5
Lamination
Number of this specification
Sign, that this designation is different from
eventual used national designations
Shape and size according to 13.3 to 13.10
Sign for holes, H with holes, X without holes
Material in accordance with Table 1
IEC  1195/05
60740-1  IEC:2005 – 15 –
5.1.2 Specified shape with lamination strips

LAM IEC 60740-1 YSUI 1-50 X M 165-35S 5
Lamination
Number of this standard
Sign, that this designation is different from eventual
used national designations
Sign, that the shape is made of lamination strips
Shape and size according to 13.4.2 or 13.5.2
Sign for holes, H with holes, X without holes
Material in accordance with Table 1
IEC  1196/05
5.2 Lamination strips for specified shapes
5.2.1 Lamination strips for yokes

LAM IEC 60740-1 YSUI 1-50 Y X M 165-35S 5
Lamination
Number of this standard
Sign, that this designation is different from eventual
used national designations
Sign, that the shape is made of lamination strips
Shape and size according to 13.4.2 or 13.5.2
Sign for lamination strips for yokes
Sign for holes, H with holes, X without holes
Material in accordance with Table 1
IEC  1197/05
5.2.2 Lamination strips for limbs

LAM IEC 60740-1 YSUI 1-50 L X M 165-35S 5
Lamination
Number of this standard
Sign, that this designation is different from eventual
used national designations
Sign, that the shape is made of lamination strips
Shape and size according to 13.4.2 or 13.5.2
Sign for lamination strips for limbs
Sign for holes, H with holes, X without holes
Material in accordance with Table 1
IEC  1198/05
– 16 – 60740-1  IEC:2005
5.3 Lamination strips for non-specified laminations

LAM IEC 60740-1 YS100  500 X M 165-35S 5
Lamination
Number of this standard
Sign, that this designation is different from eventual
used national designations
Lamination strips according to 13.2
Width of the lamination strip in mm
Length of the lamination strip in mm
Sign for holes, H with holes, X without holes
Material in accordance with Table 1
IEC  1199/05
6 Packing and marking
The laminations shall be packed for transit in such a manner that no deterioration will occur.
Unless otherwise specified, all parts designing a layer of lamination shall be packed in one
packaging unit.
All packages shall be marked with the following information:
– lamination designation;
– quantity by mass or by number;
– the manufacturer’s lot identification or date of manufacture;
– manufacturer.
Example of marking:
– lamination: LAM IEC 60740-1 YEI 1-40 H M 330-35A 5
– quantity:
– date of manufacture:
– manufacturer:
7 Electrical tests
7.1 General
Electrical tests for stacked laminations shall be carried out for the appropriate materials
specified in Table 1 according to the test parameters specified in Tables 5, 6 and 7. Effective
parameters see 7.2 to 7.4.
7.2 Core constants
The core constants of laminations are calculated as follows:
l
Fe
C  (7)
A
Fe
l
Fe
C  (8)
A
Fe
60740-1  IEC:2005 – 17 –
where
–1
is the core constant 1, in mm ;
C
–3;
C is the core constant 2, in mm
l is the magnetic path length, in mm, calculated as in 7.3;
Fe
A is the core cross-section, in mm , taking into account the stacking factor η, see 7.4.
Fe
Further, the core volume, in mm , and the core mass, in kg, are calculated as follows:
V = l · A (9)
Fe Fe Fe
m = V · ρ (10)
Fe Fe
where ρ is the density of the alloy, in kg/dm .
The effective parameters of laminated cores with square cross-section and a stacking factor
of 0,95 are shown in Tables 17, 18, 19, 20, 21, 22, 23, 24, 25, 26 and 27. For the laminations
in 13.3, 13.4.1 and 13.5.1 the equations for the core constants are given subsequent to the
associated tables.
7.3 Magnetic path length
The magnetic path length l is calculated as the arithmetic mean of the longest and the
Fe
shortest path length of the core neglecting radii.
NOTE For details on the calculation for each core, see 13.3, 13.4.1 and 13.5.1.
7.4 Core cross-section
The core cross-section is calculated as the product of (centre) limb width, stack height and
stacking factor:
A = d · h · η (11)
Fe p
where
A is the core cross-section, in mm ;
Fe
d is the limb width, in mm;
h is the stack height, in mm;
p
 is the stacking factor.
For cores with square stack (h = d) shown in Tables 17, 18, 19, 20, 21, 22, 23, 24, 25, 26
p
and 27 and with η = 0,95, the core cross-section is:
A = 0,95 · d (12)
Fe
For other stack heights and stacking factors differing from Table 4, the values for A and C
Fe 1
shall be corrected by multiplying with the following factors:
h 
p
The factor for A is:
Fe
d 0,95
d 0,95
The factor for C is:
h 
p
– 18 – 60740-1  IEC:2005
NOTE Alternatively, for a given core stack, the core cross-section may be determined as follows:
m
Fe
For YEI, YEx, YUI and YM: A  (13)
Fe
l 
Fe
8 General conditions for electrical measurements
8.1 Atmospheric conditions
Unless otherwise stated, all tests shall be carried out at room temperature.
8.2 Test coils
The electrical tests in Clauses 15 and 16 are valid for the square stack. The stack height of
the test coil and of the core may be changed, if the values are not changed. However, the
test coils shall be suitable to the stack of laminations to be tested. The voltage winding N
shall be the inner winding and be as close as possible to the core, and its resistance R shall
be small compared to the resistance of its load.
The resistance in the supply circuit, including the coil resistance R and the resistance of the
current measuring device (current meter, current amplifier or precision resistor), shall be
small, so that they do not result in any appreciable distortion of the voltage.
8.3 Test cores
The laminations shall physically be in accordance with the requirements of Clauses 4 and 13
and shall be selected at random from those which are fully processed for the end application.
They shall be interleaved as a stack and shall consist of equal numbers of all necessary parts
designing a complete layer of lamination.
NOTE Using grain-oriented and non-oriented silicon steel the laminations may be interleaved equilateral. Only in
case of arbitration they shall be interleaved one by one throughout the stack.
Test cores made of lamination strips are a matter of agreement between customer and
manufacturer.
8.4 Harmonic content of the voltage
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