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

IEC 62024-2:2020 is available as IEC 62024-2:2020 RLV which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition.
IEC 62024-2:2020 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 document 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 document (no larger than a 12 mm x 12 mm footprint approximately). These inductors are typically used in DC-to-DC converters built on PCBs, 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. This edition includes the following significant technical changes with respect to the previous edition:
- addition of Table 2 and Figure 2 b).

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

IEC 62024-2:2020 est disponible sous forme de IEC 62024-2:2020 RLV qui contient la Norme internationale et sa version Redline, illustrant les modifications du contenu technique depuis l'édition précédente.
L'IEC 62024-2:2020 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 caractéristiques assignées permettent aux utilisateurs de comparer avec précision les caractéristiques assignées courantes figurant dans les différents recueils de données fabricants. Le présent document s'applique aux bobines d'induction à sorties et pour montage en surface dont les dimensions sont conformes à l'IEC 62025-1 et dont le courant assigné est généralement inférieur à 22 A, même si des bobines d'induction de courant assigné supérieur à 22 A sont disponibles et respectent les restrictions de dimensions de ce document (empreinte ne dépassant pas environ 12 mm x 12 mm). Ces bobines d'induction sont habituellement utilisées dans des convertisseurs continu-continu 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. Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
- ajout du Tableau 2 et de la Figure 2 b).

General Information

Status
Published
Publication Date
30-Mar-2020
Current Stage
PPUB - Publication issued
Completion Date
31-Mar-2020
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IEC 62024-2
Edition 2.0 2020-03
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
continu-continu
IEC 62024-2:2020-03(en-fr)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC 62024-2
Edition 2.0 2020-03
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
continu-continu
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.100.10 ISBN 978-2-8322-7995-3

Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 3 ----------------------
– 2 – IEC 62024-2:2020 © IEC 2020
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 Measuring circuit and calculation ............................................................................ 7

5.3.1 Measuring circuit ............................................................................................. 7

5.3.2 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 Measuring jig .......................................................................................................... 9

6.3.1 General ........................................................................................................... 9

6.3.2 Printed-wiring board method ............................................................................ 9

6.3.3 Lead wire method .......................................................................................... 12

6.4 Measuring method and calculation ........................................................................ 12

6.4.1 General ......................................................................................................... 12

6.4.2 Resistance substitution method ..................................................................... 12

6.4.3 Thermo-couple method .................................................................................. 14

6.5 Quality conformance inspection ............................................................................ 15

7 Determination of rated current ....................................................................................... 15

8 Information to be given in the detail specification ........................................................... 15

8.1 General ................................................................................................................. 15

8.2 Measuring method of DC saturation limited current ............................................... 15

8.3 Measuring method of temperature rise limited current ........................................... 15

Annex A (informative) Example of recommended description on product specification

sheets and catalogues .......................................................................................................... 16

Bibliography .......................................................................................................................... 17

Figure 1 – Inductance measuring circuit under application of DC saturation condition ............ 7

Figure 2 – Example of printed-wiring boards ......................................................................... 12

Figure 3 – Temperature rise measuring circuit by resistance substitution method ................ 13

Figure 4 – Temperature rise measuring circuit by thermo-couple method .............................. 14

Table 1 – Width of circuits ...................................................................................................... 9

Table 2 – Circuit pattern width and thickness ........................................................................ 10

Table 3 – Wire size of circuits ............................................................................................... 12

---------------------- Page: 4 ----------------------
IEC 62024-2:2020 © IEC 2020 – 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 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

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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

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between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in

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assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any

services carried out by independent certification bodies.

6) All users should ensure that they have the latest edition of this publication.

7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and

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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, ferrite and magnetic powder materials.

This second edition cancels and replaces the first edition published in 2008. This edition

constitutes a technical revision.

This edition includes the following significant technical changes with respect to the previous

edition:
a) addition of Table 2 and Figure 2 b).
The text of this International Standard is based on the following documents:
CDV Report on voting
51/1303/CDV 51/1325/RVC
---------------------- Page: 5 ----------------------
– 4 – IEC 62024-2:2020 © IEC 2020

Full information on the voting for the approval of this International Standard can be found in

the report on voting indicated in the above table.

This document has been drafted in accordance with the ISO/IEC Directives, Part 2.

A list of all parts of IEC 62024 series, published 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 document will remain unchanged until the

stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to

the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
---------------------- Page: 6 ----------------------
IEC 62024-2:2020 © IEC 2020 – 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 document 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

document (no larger than a 12 mm × 12 mm footprint approximately). These inductors are

typically used in DC-to-DC converters built on PCBs, 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 documents are referred to in the text in such a way that some or all of their

content constitutes requirements 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 60068-1:2013, 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.

ISO and IEC maintain terminological databases for use in standardization at the following

addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
DC saturation limited current

allowable value of DC current for which the decrease of the inductance is within the specified

value
---------------------- Page: 7 ----------------------
– 6 – IEC 62024-2:2020 © IEC 2020
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
4 Standard atmospheric conditions
4.1 Standard atmospheric conditions for testing

Standard atmospheric conditions for testing shall be as follows (see IEC 60068-1:2013, 4.3):

– 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 IEC 60068-1:2013, 4.2, 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 document, 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 is 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 document 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 document 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 ----------------------
IEC 62024-2:2020 © IEC 2020 – 7 –
5.3 Measuring circuit and calculation
5.3.1 Measuring circuit
The measuring circuit is as shown in Figure 1.
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
I supplied current to range resistor
I supplied current to specimen
I = I
x r
Figure 1 – Inductance measuring circuit under
application of DC saturation condition
5.3.2 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 formulae.
E −E
ZR
r 2
Z Z cosθθ+ jZ sin
xx x
Z R+ jX
xx x
ωπ2 f
where
---------------------- Page: 9 ----------------------
– 8 – IEC 62024-2:2020 © IEC 2020
R is the resistance of the specimen;
X is the reactance of the specimen;
Z is the impedance of the specimen;
L is the equivalent series inductance of the specimen;
E is the applied voltage to the specimen;

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

2 r r 2
θ is the phase angle difference between E and E
1 2
5.4 Attachment jig of inductor

The attachment jig of the specimen shall be specified in the detail specification.

5.5 Measuring method
a) 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 formulae of 5.3.2.

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 document defines the temperature rise induced only by DC currents.

AC copper losses and AC core losses are considered 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 is an unlimited

number of different ways to apply AC current in an application. Therefore, manufacturers and users have generally

defined DC temperature rise limited current as a common point of reference. This document does the same.

---------------------- Page: 10 ----------------------
IEC 62024-2:2020 © IEC 2020 – 9 –
6.2 Test conditions

Unless otherwise specified in the detail specification, for example an elevated ambient

temperature, 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 are dependent on the magnetic material type and grade.

Some ferrites exhibit sharp minima temperatures. These considerations are 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 can be dominated by DC loss or

AC loss depending 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 modeled. Measurement at room temperature is

commonly applied for detail specifications. In any event, the ambient temperature for the test is specified in the

detail specification.
6.3 Measuring jig
6.3.1 General

The measuring jig shall be either printed-wiring board method given in 6.3.2 or lead wire

method given in 6.3.3, and shall be specified in the detail specification.
6.3.2 Printed-wiring board method

The 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, Table 2 and

Figure 2.
Table 1 – Width of circuits
Rated current class Rated current of inductor Pattern width
I W
A mm
I ≤ 1 1,0 ± 0,2
class A
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
22 < I According to the detail specification
NOTE See Figure 2a).
---------------------- Page: 11 ----------------------
– 10 – IEC 62024-2:2020 © IEC 2020
Table 2 – Circuit pattern width and thickness
Rated current Pattern width Pattern thickness Example application
class W t
mm µm
I (1,0 to 22,0) ± 0,2 35 ± 10 Consumer application (single-sided printed circuit
class A
to 0,5 boards application)
I 40 ± 0,2 35 ± 10 Consumer application (double-sided printed circuit
class B
boards application)
I 40 ± 0,2 105 ± 10 Consumer application (multilayer printed circuit
class C
boards application)
I 40 ± 0,2 1000 ± 50 Automotive or large current power line application
class D
NOTE 1 I : see Figure 2a).
class A
NOTE 2 I I I : see Figure 2b).
class B, class C, class D
Dimensions in millimetres
a) Example of printed-wiring board for SMD type (I class A)
---------------------- Page: 12 ----------------------
IEC 62024-2:2020 © IEC 2020 – 11 –
b) Example of printed-wiring board for SMD type (I class B,C,D)
Dimensions in millimetres
c) Example of printed-wiring board for leaded type
Key

Solderable areas (only the recommended land pattern should be covered by soldering)

---------------------- Page: 13 ----------------------
– 12 – IEC 62024-2:2020 © IEC 2020
Current applying connection areas
Voltage measuring areas

(Voltage should be measured at the product's electrodes in case the DC resistance of the

product is lower than the pattern resistance)
Non-solderable areas (covered with non-solderable lacquer)
Cu areas
NOTE 1 a, b, c, d , d and p: according to the detail specification.
1 2
NOTE 2 Material of sub
...

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