IEC 62024-2:2008

High frequency inductive components - Electrical characteristics and measuring methods - Part 2: Rated current of inductors for DC to DC converters

IEC 62024-2:2008 specifies the measuring methods of the rated direct current limits for small inductors. Standardized measuring methods for the determination of ratings enable users to accurately compare the current ratings given in various manufacturers' data books. This standard is applicable to leaded and surface mount inductors with dimensions according to IEC 62025-1 and generally with rated current less than 22 A, although inductors with rated current greater than 22 A are available that fall within the dimension restrictions of this standard (no larger than 12 mm x 12 mm footprint approximately). These inductors are typically used in DC to DC converters built on PCB, for electric and telecommunication equipment, and small size switching power supply units. The measuring methods are defined by the saturation and temperature rise limitations induced solely by direct current.

Composants inductifs à haute fréquence - Caractéristiques électriques et méthodes de mesure - Partie 2: Courant assigné des bobines d'induction pour des convertisseurs continus-continus

La CEI 62024-2:2008 spécifie les méthodes de mesure des limites de courant continu assigné pour de petites bobines d'induction. Les méthodes de mesure normalisées pour la détermination des valeurs nominales permettent aux utilisateurs de comparer précisément les valeurs nominales courantes figurant dans les différents recueils de données fabricants. La présente norme s'applique aux bobines d'induction à sorties et pour montage en surface dont les dimensions sont conformes à la CEI 62025-1 et dont généralement le courant assigné est inférieur à 22 A, même si des bobines d'induction de courant assigné supérieur à 22 A sont disponibles et s'intègrent dans les restrictions de dimensions de cette norme (empreinte ne dépassant pas 12 mm x 12 mm, approximativement). Ces bobines d'induction sont typiquement utilisées dans des convertisseurs continus-continus montés sur des cartes à circuit imprimé (CCI), pour des matériels électriques et de télécommunications, ainsi que pour des unités d'alimentation de puissance de commutation de petite taille. Les méthodes de mesure sont définies par les limites de saturation et d'échauffement induites uniquement par le courant continu.

General Information

• Status: Published
• Publication Date: 07-Oct-2008
• ICS: 29.100.10 - Magnetic components
• Technical Committee: TC 51 - Magnetic components, ferrite and magnetic powder materials
• Drafting Committee: WG 9 - TC 51/WG 9
• Current Stage: DELPUB - Deleted Publication
• Start Date: 28-Dec-2018
• Completion Date: 31-Mar-2020

Relations

• Revised: IEC 62024-2:2020 - High frequency inductive components - Electrical characteristics and measuring methods - Part 2: Rated current of inductors for DC-to-DC converters
• Effective Date: 05-Sep-2023

Standards Content (Sample)

IEC 62024-2



Edition 1.0 2008-10



INTERNATIONAL



STANDARD






High frequency inductive components – Electrical characteristics and measuring
methods –
Part 2: Rated current of inductors for DC to DC converters




IEC 62024-2:2008(E)

---------------------- Page: 1 ----------------------
THIS PUBLICATION IS COPYRIGHT PROTECTED

Copyright © 2008 IEC, Geneva, Switzerland



All rights reserved. Unless otherwise specified, 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
 either IEC or IEC's member National Committee in the country of the requester.
If you have any questions about IEC copyright or have an enquiry about obtaining additional rights to this publication,

please contact the address below or your local IEC member National Committee for further information.



IEC Central Office
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Switzerland
 Email: [e-mail]
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About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigenda or an amendment might have been published.
ƒ Catalogue of IEC publications: 2Hwww.iec.ch/searchpub
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in English and French, with equivalent terms in additional languages. Also known as the International Electrotechnical
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Centre FAQ or contact us:
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---------------------- Page: 2 ----------------------
IEC 62024-2



Edition 1.0 2008-10



INTERNATIONAL



STANDARD





High frequency inductive components – Electrical characteristics and measuring
methods –
Part 2: Rated current of inductors for DC to DC converters



INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
Q
ICS 29.100.10 ISBN 978-2-88910-607-3
® Registered trademark of the International Electrotechnical Commission

---------------------- Page: 3 ----------------------
– 2 – 62024-2 © IEC:2008(E)



CONTENTS

FOREWORD.3


1 Scope.5

2 Normative references .5

3 Terms and definitions .5


4 Standard atmospheric conditions.6

4.1 Standard atmospheric conditions for testing .6


4.2 Reference conditions.6

5 Measuring method of DC saturation limited current.6
5.1 General .6
5.2 Test conditions.6
5.3 Measurement circuit and calculation.7
5.4 Attachment jig of inductor.8
5.5 Measuring method.8
5.6 Quality conformance inspection.8
6 Measuring method of temperature rise limited current .8
6.1 General .8
6.2 Test conditions.9
6.3 Measurement jig.9
6.3.1 Printed-wiring board method.9
6.3.2 Lead wire method .11
6.4 Measuring method and calculation .12
6.4.1 Resistance-substitution method .12
6.4.2 Thermo-couple method.13
6.5 Quality conformance inspection.14
7 Determination of rated current .14
8 Information to be given in the detail specification.14
8.1 Measuring method of DC saturation limited current .14
8.2 Measuring method of temperature rise limited current .15
Annex A (informative) Example of recommended description on product specification
sheets and catalogues .16

Figure 1 – Inductance measurement circuit under application of DC saturation

7
condition.
Figure 2a) – Example of printed-wiring board for SMD type .10
Figure 2b) – Example of printed-wiring board for leaded type.11
Figure 2 – Example of printed-wiring board.11
Figure 3 – Temperature rise measurement circuit by resistance substitution method.12
Figure 4 – Temperature rise measurement circuit by thermo-couple method .13

Table 1 – Width of circuits .9
Table 2 – Wire size of circuits .12

---------------------- Page: 4 ----------------------
62024-2 © IEC:2008(E) – 3 –


INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________



 HIGH FREQUENCY INDUCTIVE COMPONENTS –

ELECTRICAL CHARACTERISTICS AND MEASURING METHODS –



Part 2: Rated current of inductors for DC to DC converters






FOREWORD

1) The International Electrotechnical Commission (IEC) 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, 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.
International Standard IEC 62024-2 has been prepared IEC technical committee 51: Magnetic
components and ferrite materials.
The text of this standard is based on the following documents:
FDIS Report on voting
51/937/FDIS 51/941/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.
A list of all parts of IEC 62024 series, under the general title High frequency inductive
components – Electrical characteristics and measuring methods, can be found on the IEC
website.

---------------------- Page: 5 ----------------------
– 4 – 62024-2 © IEC:2008(E)


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.

---------------------- Page: 6 ----------------------
62024-2 © IEC:2008(E) – 5 –


HIGH FREQUENCY INDUCTIVE COMPONENTS –

ELECTRICAL CHARACTERISTICS AND MEASURING METHODS –



 Part 2: Rated current of inductors for DC to DC converters








1 Scope



This part of IEC 62024 specifies the measuring methods of the rated direct current limits for
small inductors.
Standardized measuring methods for the determination of ratings enable users to accurately
compare the current ratings given in various manufacturers’ data books.
This standard is applicable to leaded and surface mount inductors with dimensions according
to IEC 62025-1 and generally with rated current less than 22 A, although inductors with rated
current greater than 22 A are available that fall within the dimension restrictions of this
standard (no larger than 12 mm × 12 mm footprint approximately). These inductors are
typically used in DC to DC converters built on PCB, for electric and telecommunication
equipment, and small size switching power supply units.
The measuring methods are defined by the saturation and temperature rise limitations
induced solely by direct current.
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 60068-1, Environmental testing – Part 1: General and guidance
IEC 62025-1, High frequency inductive components – Non-electrical characteristics and
measuring methods – Part 1: Fixed, surface mounted inductors for use in electronic and
telecommunication equipment
3 Terms and definitions

For the purposes of this document, the following terms and definitions apply.
3.1
DC saturation limited current
allowable value of DC current for which the decrease of the inductance is within the specified
value
3.2
temperature rise limited current
allowable value of DC current for which the self-generation heat of the inductor results in
temperature rise within the specified value

---------------------- Page: 7 ----------------------
– 6 – 62024-2 © IEC:2008(E)


4 Standard atmospheric conditions


4.1 Standard atmospheric conditions for testing


Standard atmospheric conditions for testing shall be as follows (see 5.3.1 of IEC 60068-1):


– temperature: 15 °C to 35 °C;

– relative humidity: 25 % to 75 %;

– air pressure: 86 kPa to 106 kPa.



In the event of dispute or where required, the measurements shall be repeated using the

referee temperatures and such other conditions as given in 4.2.
4.2 Reference conditions
For reference purposes, one of the standard atmospheric conditions for referee tests taken
from 5.2 of IEC 60068-1 shall be selected and shall be as follows:
– temperature: 20 °C ± 2 °C;
– relative humidity: 60 % to 70 %;
– air pressure: 86 kPa to 106 kPa.
5 Measuring method of DC saturation limited current
5.1 General
When alternating current in which DC current is superimposed is supplied to an inductor, the
inductance of the inductor decreases according to the DC current value.
In a typical application, the saturation current results from the peak current of the
superposition of AC on DC current. In this standard, the saturation current is measured as DC
current offsetting a small signal AC current.
NOTE It is not practical to set a standard for AC saturation limited current, because there are an unlimited
number of different ways to apply AC current in an application. Therefore, manufacturers and users have generally
defined DC saturation limited current as a common point of reference. This standard does the same.
5.2 Test conditions
Unless otherwise specified in the detail specification, the test conditions shall be in
accordance with Clause 4.

NOTE The variation of the value of DC saturation limited current, as a function of temperature, is dependent on
the magnetic material and the structure of the magnetic core of the inductor. However, measurement of DC
saturating currents at elevated temperatures is generally not practical for inspection purposes. Therefore, the
measurement at room temperature as provided by this standard is generally applied for specification purposes. De-
rating curves indicating variation of DC saturation limited current as a function of maximum operating temperature
of the inductor can be generated. These curves can be used to correlate the DC saturation limited current at room
temperature to the DC saturation limited current at typical operating temperatures. In some cases, it will become
necessary for the manufacturer and user to agree on an additional specification at a high temperature such as
85 °C, 105 °C or 125 °C.

---------------------- Page: 8 ----------------------
62024-2 © IEC:2008(E) – 7 –


 5.3 Measurement circuit and calculation

a) Measuring circuit


The measuring circuit is as shown in Figure 1.


DC superimposed current supply



Virtual ground



Specimen
I
C
x C I
R
R r
 s
r
C C
–
V
1
OSC f
s
E
1
+
E
V
2
2
IEC  1726/08

Components
R source resistor R = R
s s
R range resistor R = R
r r
V voltmeter V = E
1 1 1
V voltmeter V = E

2 2 2
C DC current blocking capacitor
Supplies
f frequency of source
s
I supplied current to range resistor
r
I supplied current to specimen
x
I = I
x r
Figure
...

IEC 62024-2


®

Edition 1.0 2008-10



INTERNATIONAL



STANDARD



NORME
INTERNATIONALE


High frequency inductive components – Electrical characteristics and measuring
methods –
Part 2: Rated current of inductors for DC to DC converters

Composants inductifs à haute fréquence – Caractéristiques électriques et
méthodes de mesure –
Partie 2: Courant assigné des bobines d’induction pour des convertisseurs
continus-continus


IEC 62024-2:2008

---------------------- Page: 1 ----------------------
THIS PUBLICATION IS COPYRIGHT PROTECTED


Copyright © 2008 IEC, Geneva, Switzerland

All rights reserved. Unless otherwise specified, 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 either IEC or

IEC's member National Committee in the country of the requester.
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Email: [e-mail]
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About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigenda or an amendment might have been published.
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in English and French, with equivalent terms in additional languages. Also known as the International Electrotechnical
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---------------------- Page: 2 ----------------------
IEC 62024-2


®

Edition 1.0 2008-10



INTERNATIONAL



STANDARD



NORME
INTERNATIONALE


High frequency inductive components – Electrical characteristics and measuring
methods –
Part 2: Rated current of inductors for DC to DC converters

Composants inductifs à haute fréquence – Caractéristiques électriques et
méthodes de mesure –
Partie 2: Courant assigné des bobines d’induction pour des convertisseurs
continus-continus


INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
Q
CODE PRIX
ICS 29.100.10 ISBN 978-2-88910-608-0
® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale

---------------------- Page: 3 ----------------------
– 2 – 62024-2 © IEC:2008



CONTENTS

FOREWORD.3


1 Scope.5

2 Normative references .5

3 Terms and definitions .5


4 Standard atmospheric conditions.6

4.1 Standard atmospheric conditions for testing .6

4.2 Reference conditions.6

5 Measuring method of DC saturation limited current.6
5.1 General .6
5.2 Test conditions.6
5.3 Measurement circuit and calculation.7
5.4 Attachment jig of inductor.8
5.5 Measuring method.8
5.6 Quality conformance inspection.8
6 Measuring method of temperature rise limited current .8
6.1 General .8
6.2 Test conditions.9
6.3 Measurement jig.9
6.3.1 Printed-wiring board method.9
6.3.2 Lead wire method .11
6.4 Measuring method and calculation .12
6.4.1 Resistance-substitution method .12
6.4.2 Thermo-couple method.13
6.5 Quality conformance inspection.14
7 Determination of rated current .14
8 Information to be given in the detail specification.14
8.1 Measuring method of DC saturation limited current .14
8.2 Measuring method of temperature rise limited current .15
Annex A (informative) Example of recommended description on product specification
sheets and catalogues .16

Figure 1 – Inductance measurement circuit under application of DC saturation

7
condition.
Figure 2a) – Example of printed-wiring board for SMD type .10
Figure 2b) – Example of printed-wiring board for leaded type.11
Figure 2 – Example of printed-wiring board.11
Figure 3 – Temperature rise measurement circuit by resistance substitution method.12
Figure 4 – Temperature rise measurement circuit by thermo-couple method .13

Table 1 – Width of circuits .9
Table 2 – Wire size of circuits .12

---------------------- Page: 4 ----------------------
62024-2 © IEC:2008 – 3 –


INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________



HIGH FREQUENCY INDUCTIVE COMPONENTS –

ELECTRICAL CHARACTERISTICS AND MEASURING METHODS –



Part 2: Rated current of inductors for DC to DC converters





FOREWORD

1) The International Electrotechnical Commission (IEC) 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, 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.
International Standard IEC 62024-2 has been prepared IEC technical committee 51: Magnetic
components and ferrite materials.
This bilingual version, published in 2009-02, corresponds to the English version.
The text of this standard is based on the following documents:
FDIS Report on voting
51/937/FDIS 51/941/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.

---------------------- Page: 5 ----------------------
– 4 – 62024-2 © IEC:2008


A list of all parts of IEC 62024 series, under the general title High frequency inductive

components – Electrical characteristics and measuring methods, can be found on the IEC

website.


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.

---------------------- Page: 6 ----------------------
62024-2 © IEC:2008 – 5 –


HIGH FREQUENCY INDUCTIVE COMPONENTS –

ELECTRICAL CHARACTERISTICS AND MEASURING METHODS –



Part 2: Rated current of inductors for DC to DC converters








1 Scope


This part of IEC 62024 specifies the measuring methods of the rated direct current limits for
small inductors.
Standardized measuring methods for the determination of ratings enable users to accurately
compare the current ratings given in various manufacturers’ data books.
This standard is applicable to leaded and surface mount inductors with dimensions according
to IEC 62025-1 and generally with rated current less than 22 A, although inductors with rated
current greater than 22 A are available that fall within the dimension restrictions of this
standard (no larger than 12 mm × 12 mm footprint approximately). These inductors are
typically used in DC to DC converters built on PCB, for electric and telecommunication
equipment, and small size switching power supply units.
The measuring methods are defined by the saturation and temperature rise limitations
induced solely by direct current.
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 60068-1, Environmental testing – Part 1: General and guidance
IEC 62025-1, High frequency inductive components – Non-electrical characteristics and
measuring methods – Part 1: Fixed, surface mounted inductors for use in electronic and
telecommunication equipment
3 Terms and definitions

For the purposes of this document, the following terms and definitions apply.
3.1
DC saturation limited current
allowable value of DC current for which the decrease of the inductance is within the specified
value
3.2
temperature rise limited current
allowable value of DC current for which the self-generation heat of the inductor results in
temperature rise within the specified value

---------------------- Page: 7 ----------------------
– 6 – 62024-2 © IEC:2008


4 Standard atmospheric conditions


4.1 Standard atmospheric conditions for testing


Standard atmospheric conditions for testing shall be as follows (see 5.3.1 of IEC 60068-1):


– temperature: 15 °C to 35 °C;

– relative humidity: 25 % to 75 %;

– air pressure: 86 kPa to 106 kPa.


In the event of dispute or where required, the measurements shall be repeated using the

referee temperatures and such other conditions as given in 4.2.
4.2 Reference conditions
For reference purposes, one of the standard atmospheric conditions for referee tests taken
from 5.2 of IEC 60068-1 shall be selected and shall be as follows:
– temperature: 20 °C ± 2 °C;
– relative humidity: 60 % to 70 %;
– air pressure: 86 kPa to 106 kPa.
5 Measuring method of DC saturation limited current
5.1 General
When alternating current in which DC current is superimposed is supplied to an inductor, the
inductance of the inductor decreases according to the DC current value.
In a typical application, the saturation current results from the peak current of the
superposition of AC on DC current. In this standard, the saturation current is measured as DC
current offsetting a small signal AC current.
NOTE It is not practical to set a standard for AC saturation limited current, because there are an unlimited
number of different ways to apply AC current in an application. Therefore, manufacturers and users have generally
defined DC saturation limited current as a common point of reference. This standard does the same.
5.2 Test conditions
Unless otherwise specified in the detail specification, the test conditions shall be in
accordance with Clause 4.

NOTE The variation of the value of DC saturation limited current, as a function of temperature, is dependent on
the magnetic material and the structure of the magnetic core of the inductor. However, measurement of DC
saturating currents at elevated temperatures is generally not practical for inspection purposes. Therefore, the
measurement at room temperature as provided by this standard is generally applied for specification purposes. De-
rating curves indicating variation of DC saturation limited current as a function of maximum operating temperature
of the inductor can be generated. These curves can be used to correlate the DC saturation limited current at room
temperature to the DC saturation limited current at typical operating temperatures. In some cases, it will become
necessary for the manufacturer and user to agree on an additional specification at a high temperature such as
85 °C, 105 °C or 125 °C.

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62024-2 © IEC:2008 – 7 –


5.3 Measurement circuit and calculation

a) Measuring circuit


The measuring circuit is as shown in Figure 1.


DC superimposed current supply



Virtual ground


Specimen
I
C
x C I
R
R r
s
r
C C
–
V
1
OSC f
s
E
1
+
E
V
2
2
IEC  1726/08

Components
R source resistor R = R
s s
R range resistor R = R
r r
V voltmeter V = E
1 1 1
V voltmeter V = E

2 2 2
C DC current blocking capacitor
Supplies
f frequency of source
s
I supplied current to range resistor
r
I supplied current to specimen
x
I = I
x r
Figure 1 – Inductance measurement circuit under
application of DC saturation condition
b) Calculation
Voltages E and E shall be measured when frequency f and voltage E of the signal
1 2 s s
generator are supplied in accordance with the detail specification, and an initial value of the

inductance shall be calculated by the following formulas.
E − E
1 1
Z = = R
x r
I E
r 2
Z = Z cosθ + j Z sinθ
x x x
Z = R + jX
x x x
X X
x x
L = =
x
ω 2πf
s

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– 8 – 62024-2 © IEC:2008


where


R is the resistance of the specimen;
x

X is the reactance of the specimen;
x

Z is the impedance of the specimen;

x

L is the equivalent series inductance of the specimen;
x

E is applied voltage to specimen;
1

E is applied voltage to range resistor (= I R ) (E can be regarded as current);

2 r r 2

θ is phase angle difference between E and E
.
1 2

5.4 Attachment jig of inductor
Attachment jig of specimen shall be specified in the detail specification.
5.5 Measuring method
a) Short compensation shall be done before measurement.
b) The specimen shall be connected to the circuit shown in Figure 1, by using the attachment
jig specified in 5.4.
c) When the specimen is connected by soldering, it shall be left until it becomes cool enough.
d) Voltages E and E shall be measured when frequency f and voltage E of the signal
1 2 s s
generator are supplied in accordance with the detail specification, and an initial value of
the inductance shall be calculated by the formulas of 5.3 b).
e) The value of the DC current that is superimposed on the specimen shall be modulated and
the inductance value shall be measured.
f) The decrease from the initial value of the inductance shall be calculated. DC saturation
limited current shall be determined by measuring the DC current when the decrease in
inductance matches the specified value in the detail specification.
g) The decrease in inductance that is specified in the detail specification should be 10 % or
30 %.
NOTE 10 % is one of the design points typical for sharp-saturating inductors, and 30 % is one of the design points
typical for soft-saturating inductors. See Annex A.
5.6 Quality conformance inspection
The DC current specified in the detail specification shall be supplied to a specimen in

accordance with the methods specified in 5.3 to 5.5, and then inductance shall be measured.
The decrease in inductance shall be within the specified value.

6 Measuring method of temperature rise limited current
6.1 General
When DC current is supplied to an inductor, the inductor generates heat by itself according to
the supplied DC current value because of its DC current resistance.
NOTE 1 Temperature rise results from self-heating of the inductor. The sources of heating are DC copper losses,
AC copper losses and AC core losses. This standard defines the temperature rise induced only by DC currents. In
specific applications, it is necessary to consider AC copper losses and AC core losses for the temperature rise. AC
losses are highly affected by waveform, amplitude and frequency.
NOTE 2 It is not practical to set a standard for AC temperature rise limited current, because there are an
unlimited number of different ways to apply AC current in an application. In DC to DC converters, often AC loss is
far smaller than DC loss. Therefore, manufacturers and users have generally defined DC temperature rise limited
current as a common point of reference. This standard does the same.

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62024-2 © IEC:2008 – 9 –


6.2 Test conditions


Unless otherwise specified in the detail specification, the test conditions shall be in

accordance with Clause 4.


Since the value of DC current resistance increases as a function of temperature, some

applications require a high ambient temperature such as 85 °C, 105 °C or 125 °C for the

temperature rise test.


NOTE 1 The overall power loss of an inductor is a combination of DC power loss due to DC current resistance, as
well as AC power loss due to AC current in the windings and losses due to the corresponding AC flux induced in

the magnetic core. The value of AC and DC current resistance (the conductor resistance) increases with

temperature, thus the power loss associated with conductor resistance increases with temperature. The loss
associated with the magnetic core is all due to AC excitation. The core loss decreases with increasing temperature
up to a temperature typically referred to as the core loss minima temperature, above which point this loss begins to
increase. The minima temperature and magnitude of loss is dependent on the magnetic material type and grade.
Most ferrites exhibit sharp minima temperatures, while powder alloys do not. These considerations must be taken
into account when applying temperature rise currents to applications with high operating temperatures and a non-
trivial amount of AC power loss in addition to DC power loss. The overall total loss at any given temperature may
be dominated by DC loss or AC loss dependent on the power loss distribution at room temperature as well as the
variation of each of these power losses with temperature.
NOTE 2 Regarding DC temperature rise limited currents at high temperatures, the variation in DC temperature
rise limited current with ambient temperature variation can be predicted. Moreover, measurement of DC
temperature rise limited currents at elevated temperatures is generally not practical. Therefore, the measurement
at room temperature as provided by this standard is generally applied.
6.3 Measurement jig
The measurement jig shall be either printed-wiring board method given in 6.3.1 or lead wire
method given in 6.3.2, and shall be specified in the detail specification.
6.3.1 Printed-wiring board method
Printed-wiring board shall be made of epoxide woven glass (FR4). Unless otherwise specified
in the detail specification, the dimensions shall be as shown in Table 1 and Figure 2.
Table 1 – Width of circuits
a
Rated current of inductor Pattern width
I W
A mm
I ≤ 1 1,0 ± 0,2
1< I ≤ 2 2,0 ± 0,2
2 < I ≤ 3 3,0 ± 0,3

3 < I ≤ 5 5,0 ± 0,3
5 < I ≤ 7 7,0 ± 0,5
7 < I ≤ 11 11,0 ± 0,5
11 < I ≤ 16 16,0 ± 0,5
16 < I ≤ 22
22,0 ± 0,5
According to the detail specification
22 < I
a
See Figure 2.

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– 10 – 62024-2 © IEC:2008


Dimension in millimetres





100,0 ± 1,0


10,0 ± 0,5
80,0 ± 1,0






0,035 ± 0,010
2,0 ± 0,1 2,0 ± 0,1
1,0 ± 0,1
2,0 ± 0,1
30,0 ± 0,5
bc
a W
0,2 ± 0,1 0,2 ± 0,1
IEC  1727/08


Figure 2a) – Example of printed-wiring board for SMD type


5,0 ± 0,5
20,0 ± 0,5
40,0 ± 1,0

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62024-2 © IEC:2008 – 11 –


Dimension in millimetres





100,0 ± 1,0

10,0 ± 0,5
80,0 ± 1,0






0,035 ± 0,010
2,0 ± 0,1 2,0 ± 0,1
1,0 ± 0,1
2,0 ± 0,1
30,0 ± 0,5
p
d d
1 2 W
0,2 ± 0,1 0,2 ± 0,1
IEC  1728/08

Figure 2b) – Example of printed-wiring board for leaded type
Key
 solderable areas
 non-solderable areas (covered with non-solderable lacquer)


NOTE 1 a, b, c, d , d and p: according to the detail specification.
1 2
NOTE 2 Materials of substrate: epoxide woven glass (FR4).
NOTE 3 Materials of pattern: copper.
NOTE 4 Thickness of pattern: 0,035 mm ± 0,010 mm.
NOTE 5 Pattern width (W): see Table 1.
Figure 2 – Example of printed-wiring boards
6.3.2 Lead wire method
Unless otherwise specified in the detail specification, the wire diameter of lead wire to
connect the inductor and the measurement circuit shall be in accordance with Table 2.
5,0 ± 0,5
20,0 ± 0,5
40,0 ± 1,0

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– 12 – 62024-2 © IEC:2008


Table 2 – Wire size of circuits


Rated current of inductors Wire size

I
mm AWG (for reference)
A


I ≤ 3 24
0,50 ± 0,05

22
3 < I ≤ 5 0,65 ± 0,05

5 < I ≤ 11 0,8 ± 0,1 20

11 < I ≤ 16 18
1,0 ± 0,1

16
16 < I ≤ 22 1,3 ± 0,1

According to the detail specification
22 < I
NOTE 1 The wire size refers to MIL standard (MIL-PRF-15733).
NOTE 2 AWG is a wire diameter number of American Wire Gauge.

6.4 Measuring method and calculation
Measuring method shall be either the resistance substitution method of 6.4.1 or the thermo-
couple method of 6.4.2, and shall be specified in the detail specification.
6.4.1 Resistance substitution method
a) The specimen shall be connected to the circuit shown in Figure 3, by using the
measurement jig specified in 6.3.

Voltmeter

E
x
V
R
x
Specimen
Ammeter
A
I
x
DC power supply
IEC  1729/08


Figure 3 – Temperature rise measurement circuit by resistance substitution method

b) When the specimen is connected by soldering, it shall be left until it becomes cool enough.
c) The specimen should be measured inside a cubic box of roughly 20 cm on each side to
prevent temperature change from air flow. The box may have some vents in the top to
prevent trapping heat inside.
The specimen shall be measured on the condition that it does not contact directly to the
test board. When it is measured by mounting on the printed-wir
...