IEC 62024-2:2020

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

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

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
• 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: 19-Dec-2024
• Completion Date: 30-Dec-2021

Relations

• Revises: IEC 62024-2:2008 - 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
• Revised: IEC 62024-2:2024 - 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 2.0 2020-03
REDLINE VERSION
INTERNATIONAL
STANDARD
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inside
High frequency inductive components – Electrical characteristics and measuring
methods –
Part 2: Rated current of inductors for DC-to-DC converters

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IEC 62024-2 ®
Edition 2.0 2020-03
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
High frequency inductive components – Electrical characteristics and measuring

methods –
Part 2: Rated current of inductors for DC-to-DC converters

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.100.10 ISBN 978-2-8322-8136-9

– 2 – IEC 62024-2:2020 RLV © IEC 2020
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Standard atmospheric conditions . 7
4.1 Standard atmospheric conditions for testing . 7
4.2 Reference conditions . 7
5 Measuring method of DC saturation limited current . 7
5.1 General . 7
5.2 Test conditions . 7
5.3 Measurement Measuring circuit and calculation . 8
5.3.1 Measuring circuit . 8
5.3.2 Calculation . 8
5.4 Attachment jig of inductor . 9
5.5 Measuring method . 9
5.6 Quality conformance inspection . 9
6 Measuring method of temperature rise limited current. 9
6.1 General . 9
6.2 Test conditions . 10
6.3 Measurement Measuring jig . 10
6.3.1 General . 10
6.3.2 Printed-wiring board method . 10
6.3.3 Lead wire method . 13
6.4 Measuring method and calculation . 14
6.4.1 General . 14
6.4.2 Resistance substitution method . 14
6.4.3 Thermo-couple method . 15
6.5 Quality conformance inspection . 17
7 Determination of rated current . 17
8 Information to be given in the detail specification . 17
8.1 General . 17
8.2 Measuring method of DC saturation limited current . 17
8.3 Measuring method of temperature rise limited current . 17
Annex A (informative) Example of recommended description on product specification
sheets and catalogues . 18
Bibliography . 19

Figure 1 – Inductance measurement measuring circuit under application
of DC saturation condition . 8
Figure 2 – Example of printed-wiring boards . 13
Figure 3 – Temperature rise measurement measuring circuit by resistance substitution
method . 14
Figure 4 – Temperature rise measurement measuring circuit by thermo-couple method . 16

Table 1 – Width of circuits . 10

Table 2 – Circuit pattern width and thickness . 11
Table 3 – Wire size of circuits . 14

– 4 – IEC 62024-2:2020 RLV © IEC 2020
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
HIGH FREQUENCY INDUCTIVE COMPONENTS –
ELECTRICAL CHARACTERISTICS AND MEASURING METHODS –

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

FOREWORD
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This redline version of the official IEC Standard allows the user to identify the changes
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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
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.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
– 6 – IEC 62024-2:2020 RLV © IEC 2020
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
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 5.3.1 of 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 5.2 of 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.

– 8 – IEC 62024-2:2020 RLV © IEC 2020
5.3 Measurement 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
s
I supplied current to range resistor
r
I supplied current to specimen
x
I = I
x r
Figure 1 – Inductance measurement 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
xr
IE
r 2
Z Z cosθθ+ jZ sin
xx x
Z R+ jX
xx x
XX
xx
L
x
ωπ2 f
s
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 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. In
specific applications, it is necessary to consider 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. 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 document does the same.

– 10 – IEC 62024-2:2020 RLV © IEC 2020
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.
Most Some ferrites exhibit sharp minima temperatures, while powder alloys do not. These considerations must be
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 may 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 predicted modeled. 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. 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 Measurement Measuring jig
6.3.1 General
The measurement 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
a
Rated current of inductor Pattern width
Rated current class
I W
A mm
I
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
According to the detail specification
22 < I
a
NOTE See Figure 2a).
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)

– 12 – IEC 62024-2:2020 RLV © IEC 2020

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)
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 substrate: epoxide woven glass (FR4).
NOTE 3 Material of patterned areas: copper.
NOTE 4 Thickness of pattern: 0,035 mm ± 0,010 mm.
NOTE 54 Pattern width (W): see Table 1 and Table 2.

NOTE 5 e , e , e , f , f , f , f and f : according to the detail specification

1 2 3 1 2 3 4 5
Figure 2 – Example of printed-wiring boards
6.3.3 Lead wire method
Unless otherwise specified in the detail specification, the wire diameter of the lead wire to
connect the inductor and the measurement measuring circuit shall be in accordance with
Table 3.
– 14 – IEC 62024-2:2020 RLV © IEC 2020
Table 3 – Wire size of circuits
Rated current of inductors Wire size
I
mm AWG (for reference)
A
I ≤ 3 0,50 ± 0,05
3 < I ≤ 5 0,65 ± 0,05 22
5 < I ≤ 11 0,8 ± 0,1 20
11 < I ≤ 16 1,0 ± 0,1
16 < I ≤ 22 1,3 ± 0,1 16
22 < I According to the detail specification
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
6.4.1 General
The measuring method shall be either the resistance substitution method of 6.4.2 or the
thermo-couple method of 6.4.3, and shall be specified in the detail specification.
6.4.2 Resistance substitution method
a) The specimen shall be connected to the circuit shown in Figure 3, by using the
measurement measuring jig specified in 6.3.

Figure 3 – Temperature rise measurement measuring circuit
by resistance substitution method
b) When the specimen is connected by soldering, it shall be left until it becomes cool enough
cools to the test ambient.
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 with the
test board. When it is measured by mounting on the printed-wiring board, the printed-
circuit board on which the specimen is mounted shall not contact directly with the test
board.
d) The resistance value of the specimen and ambient temperature t shall be measured
a1
before DC current is supplied.

e) DC current shall be supplied to the specimen from a direct power supply. After the DC
voltage value of the specimen becomes steady, DC current value I and DC voltage value
x
E shall be measured by the ammeter and the voltmeter, and also ambient temperature ta2
x
shall be measured. Then the resistance value R shall be calculated by the following
x
formula.
E
x
R =
x
I
x
where
I is the DC current value;
x
E is the DC voltage;
x
R is the resistance of the specimen.
x
f) The temperature rise value t of the specimen shall be calculated by the following formula,
by using the resistivity coefficient of the metal and the resistance of the specimen.
t – t  shall be 5 °C or less.
a1 a2

R −R
t=t− t = Ct+ +−t t
( )
2 a2  a1 a1 a2
R
1
where
t is the temperature rise value (°C);
t is the temperature of the specimen when DC current is supplied (°C);
t is the initial ambient temperature (°C);
a1
t is the ambient temperature when DC current is supplied (°C);
a2
R is the resistance of winding at temperature t = t (Ω);

1 1 a1
R is the resistance of winding at temperature t (Ω);
2 2
C is a material constant. C for copper = 234,5.
g) The value of the supplied DC current shall be modulated and the temperature rise value
shall be measured.
h) The temperature rise limited current shall be determined by measuring DC current when
the temperature rise value becomes the specified value in the detail specification. Two
consecutive temperature readings are made, 1 min apart and shown not to vary by more
than 1°.
i) The temperature rise value that is specified in the detail specification should be 20 °C or
40 °C.
6.4.3 Thermo-couple method
a) The specimen shall be connected to the circuit shown in Figure 4, by using the
measurement measuring jig specified in 6.3.

– 16 – IEC 62024-2:2020 RLV © IEC 2020

Figure 4 – Temperature rise measurement measuring circuit by thermo-couple method
b) When the specimen is connected by soldering, it shall be left until it becomes cool enough
cools to the test ambient.
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 with the
test board. When it is measured by mounting on the printed-wiring board, the printed-
wiring board on which the specimen is mounted shall not contact directly with the test
board.
d) Consideration shall be given to the correct measurement measuring position of the
thermo-couple for the temperature measurement. It should be placed at the location where
the maximum temperature of the inductor will occur. The best location may be direct
contact at the surface of the specimen, or within the coil by placing the thermo-couple
inside, or under the coil by positioning it prior to winding.
The measurement measuring position shall be specified in the detail specification.
e) The temperature of the specimen t and ambient temperature t shall be measured
1 a1
before DC current is supplied.
f) DC current shall be supplied to the specimen from a DC power supply. After the
temperature of the specimen becomes steady, the temperature of the specimen t and
ambient temperature t shall be measured again.
a2
Criteria of temperature stability: ∆T <1 (°C /min).
g) The value of the supplied DC current shall be modulated and the temperature rise value
shall be calculated by the following formula.
t= t− t − tt−
( ) ( )
2 a2 1 a1
where
t is the temperature rise value (°C);
t is the initial temperature of the specimen (°C);
t is the temperature of the specimen when DC current is supplied (°C);
t is the initial ambient temperature (°C);
a1
t is the ambient temperature when DC current is supplied (°C).
a2
h) The temperature rise limited current shall be determined by measuring DC current when
the temperature rise value becomes the specified value in the detail specification. Two
consecutive temperature readings are made, 1 min apart and shown not to vary by more
than 1°C.
i) The temperature rise value that is specified in the detail specification should be 20 °C or
40 °C.
6.5 Quality conformance inspection
The DC current specified in the detail specification shall be supplied to a specimen in
accordance with the methods specified in 6.3 to 6.4, and then the temperature rise value shall
be measured.
The temperature rise value of the specimen shall be within the specified value.
7 Determination of rated current
For any inductor that is given a current rating, a DC saturation limited current value or a
temperature rise limited current value, whichever is less, defined and measured as shown in
this document, shall be adopted as the rated current.
8 Information to be given in the detail specification
8.1 General
The following information shall be given in the detail specification.
8.2 Measuring method of DC saturation limited current
a) Frequency f and voltage E (see 5.3.2, 5.5 d)).
s s
b) Attachment jig (see 5.4).
c) Allowable decrease in inductance (see 5.5 f)).
d) DC saturation limited current (see 5.6).
8.3 Measuring method of temperature rise limited current
a) Measurement Measuring jig (see 6.3).
b) Measuring method (see 6.4).
c) Temperature rise value (see 6.4.2 h), 6.4.3 h)).
d) Measurement Measuring position (if thermo-couple method applied) (see 6.4.2 d)), 6.4.3
d)).
e) Temperature rise limited current (see 6.5).

– 18 – IEC 62024-2:2020 RLV © IEC 2020
Annex A
(informative)
Example of recommended description on product
specification sheets and catalogues
Both the DC saturation limited current value and the temperature rise limited current value
should be described on product specification sheets and catalogues.
It should be specified whether the DC saturation limited current value is determined when the
allowable decrease in inductance value is at 10 % or 30 %.
Sharp saturation is defined as inductance that decreases by more than 8 % for a 10 %
increase in bias current, measured where bias current has already reduced the inductance by
30 % compared with the unbiased inductance. Soft saturation is defined as inductance that
decreases by less than 8 % for a 10 % increase in bias current, measured where bias current
has already reduced the inductance by 30 % compared with the unbiased inductance.
Sharp saturating inductors have a steep drop in inductance beyond an inflection point, and
therefore they are specified and designed to operate at load currents that are less than the
current at the inflection point. 10 % is used for a standard specification point because it is a
typical design point. Other values, such as 20 % or 30 %, may be used by mutual agreement
between manufacture and user.
Soft saturating inductors have a continual and gradual drop in inductance, without a well-
defined inflection point, and therefore they are specified and designed to operate at load
currents that typically push inductance down by 20 % to 50 %, or even more as the
application allows. 30 % is used for a standard specification point because it is a typical
design point (but not necessarily a requisite design point). Other values, such as 20 % or
50 %, may be used by mutual agreement between manufacturer and user.
It should be specified whether the temperature rise limited current value is determined when
the temperature rise of the inductor is 20 °C or 40 °C.
When the definition called a rated current is used, it should be the lower one of the DC
saturation limited current values and the temperature rise limited current values.
NOTE Unless otherwise specified in the detail specification, the operating temperature is the ambient temperature
plus the temperature rise of the inductors.

Bibliography
MIL-PRF-15733, Filters and Capacitors, Radio Frequency Interference, General Specification
for
___________
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
– 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 .
...

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
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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
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.100.10 ISBN 978-2-8322-7995-3
– 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

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
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agreement between the two organizations.
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6) All users should ensure that they have the latest edition of this publication.
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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.
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
– 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.
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
– 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.

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
s
I supplied current to range resistor
r
I supplied current to specimen
x
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
xr
IE
r 2
Z Z cosθθ+ jZ sin
xx x
Z R+ jX
xx x
XX
xx
L
x
ωπ2 f
s
where
==
=
=
==
– 8 – IEC 62024-2:2020 © IEC 2020
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 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.

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
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).
– 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)

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)

– 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 substrate: epoxide woven glass (FR4).
NOTE 3 Material of patterned areas: copper.
NOTE 4 Pattern width (W): see Table 1 and Table 2.

NOTE 5 e , e , e , f , f , f , f and f : according to the detail specification

1 2 3 1 2 3 4 5
Figure 2 – Example of printed-wiring boards
6.3.3 Lead wire method
Unless otherwise specified in the detail specification, the wire diameter of the lead wire to
connect the inductor and the measuring circuit shall be in accordance with Table 3.
Table 3 – Wire size of circuits
Rated current of inductors Wire size
I
mm AWG (for reference)
A
I ≤ 3 0,50 ± 0,05
3 < I ≤ 5 0,65 ± 0,05
5 < I ≤ 11 0,8 ± 0,1 20
11 < I ≤ 16 1,0 ± 0,1
16 < I ≤ 22 1,3 ± 0,1
22 < I According to the detail specification
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
6.4.1 General
The measuring method shall be either the resistance substitution method of 6.4.2 or the
thermo-couple method of 6.4.3, and shall be specified in the detail specification.
6.4.2 Resistance substitution method
a) The specimen shall be connected to the circuit shown in Figure 3, by using the measuring
jig specified in 6.3.
Figure 3 – Temperature rise measuring circuit
by resistance substitution method
b) When the specimen is connected by soldering, it shall be left until it cools to the test
ambient.
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 with the
test board. When it is measured by mounting on the printed-wiring board, the printed-
circuit board on which the specimen is mounted shall not contact directly with the test
board.
d) The resistance value of the specimen and ambient temperature t shall be measured
a1
before DC current is supplied.
e) DC current shall be supplied to the specimen from a direct power supply. After the DC
voltage value of the specimen becomes steady, DC current value I and DC voltage value
x
E shall be measured by the ammeter and the voltmeter, and also ambient temperature t
a2
x
shall be measured. Then the resistance value R shall be calculated by the following
x
formula.
E
x
R =
x
I
x
where
I is the DC current value;
x
is the DC voltage;
E
x
R is the resistance of the specimen.
x
f) The temperature rise value t of the specimen shall be calculated by the following formula,
by using the resistivity coefficient of the metal and the resistance of the specimen.
t – t  shall be 5 °C or less.
a1 a2
R −R
t=t− t = Ct+ +−t t
( )

2 a2 a1 a1 a2
R

where
t is the temperature rise value (°C);
t is the temperature of the specimen when DC current is supplied (°C);
– 14 – IEC 62024-2:2020 © IEC 2020
t is the initial ambient temperature (°C);
a1
t is the ambient temperature when DC current is supplied (°C);
a2
R is the resistance of winding at temperature t = t (Ω);

1 1 a1
R is the resistance of winding at temperature t (Ω);
2 2
C is a material constant. C for copper = 234,5.
g) The value of the supplied DC current shall be modulated and the temperature rise value
shall be measured.
h) The temperature rise limited current shall be determined by measuring DC current when
the temperature rise value becomes the specified value in the detail specification. Two
consecutive temperature readings are made, 1 min apart and shown not to vary by more
than 1°.
i) The temperature rise value that is specified in the detail specification should be 20 °C or
40 °C.
6.4.3 Thermo-couple method
a) The specimen shall be connected to the circuit shown in Figure 4, by using the measuring
jig specified in 6.3.
Figure 4 – Temperature rise measuring circuit by thermo-couple method
b) When the specimen is connected by soldering, it shall be left until it cools to the test
ambient.
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 with the
test board. When it is measured by mounting on the printed-wiring board, the printed-
wiring board on which the specimen is mounted shall not contact directly with the test
board.
d) Consideration shall be given to the correct measuring position of the thermo-couple for the
temperature measurement. It should be placed at the location where the maximum
temperature of the inductor will occur. The best location may be direct contact at the
surface of the specimen, or within the coil by placing the thermo-couple inside, or under
the coil by positioning it prior to winding.
The measuring position shall be specified in the detail specification.
and ambient temperature t shall be measured
e) The temperature of the specimen t
1 a1
before DC current is supplied.
f) DC current shall be supplied to the specimen from a DC power supply. After the
temperature of the specimen becomes steady, the temperature of the specimen t and
ambient temperature t shall be measured again.
a2
Criteria of temperature stability: ∆T <1 (°C /min).

g) The value of the supplied DC current shall be modulated and the temperature rise value
shall be calculated by the following formula.
t= t− t − tt−
( ) ( )
2 a2 1 a1
where
t is the temperature rise value (°C);
t is the initial temperature of the specimen (°C);
t is the temperature of the specimen when DC current is supplied (°C);
t is the initial ambient temperature (°C);
a1
t is the ambient temperature when DC current is supplied (°C).
a2
h) The temperature rise limited current shall be determined by measuring DC current when
the temperature rise value becomes the specified value in the detail specification. Two
consecutive temperature readings are made, 1 min apart and shown not to vary by more
than 1°C.
i) The temperature rise value that is specified in the detail specification should be 20 °C or
40 °C.
6.5 Quality conformance inspection
The DC current specified in the detail specification shall be supplied to a specimen in
accordance with the methods specified in 6.3 to 6.4, and then the temperature rise value shall
be measured.
The temperature rise value of the specimen shall be within the specified value.
7 Determination of rated current
For any inductor that is given a current rating, a DC saturation limited current value or a
temperature rise limited current value, whichever is less, defined and measured as shown in
this document, shall be adopted as the rated current.
8 Information to be given in the detail specification
8.1 General
The following information shall be given in the detail specification.
8.2 Measuring method of DC saturation limited current
a) Frequency f and voltage E (see 5.3.2, 5.5 d)).
s s
b) Attachment jig (see 5.4).
c) Allowable decrease in inductance (see 5.5 f)).
d) DC saturation limited current (see 5.6).
8.3 Measuring method of temperature rise limited current
a) Measuring jig (see 6.3).
b) Measuring method (see 6.4).
c) Temperature rise value (see 6.4.2 h), 6.4.3 h)).
d) Measuring position (if thermo-couple method applied) (see 6.4.2 d)), 6.4.3 d)).
e) Temperature rise limited current (see 6.5).

– 16 – IEC 62024-2:2020 © IEC 2020
Annex A
(informative)
Example of recommended description on product
specification sheets and catalogues
Both the DC saturation limited current value and the temperature rise limited current value
should be described on product specification sheets and catalogues.
It should be specified whether the DC saturation limited current value is determined when the
allowable decrease in inductance value is at 10 % or 30 %.
Sharp saturation is defined as inductance that decreases by more than 8 % for a 10 %
increase in bias current, measured where bias current has already reduced the inductance by
30 % compared with the unbiased inductance. Soft saturation is defined as inductance that
decreases by less than 8 % for a 10 % increase in bias current, measured where bias current
has already reduced the inductance by 30 % compared with the unbiased inductance.
Sharp saturating inductors have a steep drop in inductance beyond an inflection point, and
therefore they are specified and designed to operate at load currents that are less than the
current at the inflection point. 10 % is used for a standard specification point because it is a
typical design point. Other values, such as 20 % or 30 %, may be used by mutual agreement
between manufacture and user.
Soft saturating inductors have a continual and gradual drop in inductance, without a well-
defined inflection point, and therefore they are specified and designed to operate at load
currents that typically push inductance down by 20 % to 50 %, or even more as the
application allows. 30 % is used for a standard specification point because it is a typical
design point (but not necessarily a requisite design point). Other values, such as 20 % or
50 %, may be used by mutual agreement between manufacturer and user.
It should be specified whether the temperature rise limited current value is determined when
the temperature rise of the inductor is 20 °C or 40 °C.
When the rated current is used, it should be the lower one of the DC saturation limited current
values and the temperature rise limited current values.
NOTE Unless otherwise specified in the detail specification, the operating temperature is the ambient temperature
plus the temperature rise of the inductors.

Bibliography
MIL-PRF-15733, Filters and Capacitors, Radio Frequency Interference, General Specification
for
___________
– 18 – IEC 62024-2:2020 © IEC 2020
SOMMAIRE
AVANT-PROPOS . 20
1 Domaine d'application . 22
2 Références normatives . 22
3 Termes et définitions . 22
4 Conditions atmosphériques normales . 23
4.1 Conditions atmosphériques normales pour les essais . 23
4.2 Conditions de référence . 23
5 Méthode de mesure du courant continu limité en saturation . 23
5.1 Généralités . 23
5.2 Conditions d'essai . 23
5.3 Circuit de mesure et calcul . 24
5.3.1 Circuit de mesure . 24
5.3.2 Calcul . 24
5.4 Gabarit de fixation de la bobine d'induction . 25
5.5 Méthode de mesure . 25
5.6 Contrôle de conformité de la qualité . 25
6 Méthode de mesure du courant limité en échauffement . 26
6.1 Généralités . 26
6.2 Conditions d'essai . 26
6.3 Gabarit de mesure . 26
6.3.1 Généralités . 26
6.3.2 Méthode de la carte à circuit imprimé . 26
6.3.3 Méthode du fil de sortie . 30
6.4 Méthode de mesure et calcul . 31
6.4.1 Généralités . 31
6.4.2 Méthode par substitution de résistance . 31
6.4.3 Méthode du couple thermoélectrique . 32
6.5 Contrôle de conformité de la qualité . 34
7 Détermination du courant assigné. 34
8 Informations devant figurer dans la spécification particulière . 34
8.1 Généralités . 34
8.2 Méthode de mesure du courant continu limité en saturation . 34
8.3 Méthode de mesure du courant limité en échauffement . 34
Annexe A (informative) Exemple de description recommandée dans les fiches de
spécification produits et les catalogues . 35
Bibliographie . 36

Figure 1 – Circuit de mesure de l'inductance sous application de la condition de
saturation en courant continu . 24
Figure 2 – Exemple de cartes à circuits imprimés .
...