IEC 62317-12:2016

IEC 62317-12 ®
Edition 1.0 2016-09
INTERNATIONAL
STANDARD
Ferrite cores – Dimensions –
Part 12: Ring cores
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IEC 62317-12 ®
Edition 1.0 2016-09
INTERNATIONAL
STANDARD
Ferrite cores – Dimensions –
Part 12: Ring cores
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.100.10 ISBN 978-2-8322-3642-0

– 2 – IEC 62317-12:2016 © IEC 2016

CONTENTS
FOREWORD .3

1 Scope .5

2 Normative references .5

3 Terms and definitions .5

4 Abbreviated terms .5

5 Primary standards .5

5.1 General .5
5.2 Dimensions of ring-cores .5
5.2.1 Designation of dimensions .5
5.2.2 Identification of standard sizes .6
5.2.3 Effective parameter values .6
5.2.4 Dimensional limits for standard sizes .6
5.3 Coating . 14
Bibliography . 15

Table 1 – Ring core dimension designations .6
Table 2 – Standard ring cores .7
Table 3 – Effective parameters of ring cores .9
Table 4 – Uncoated ring cores recommended dimensional limits . 12

INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________
FERRITE CORES – DIMENSIONS –
Part 12: Ring cores
FOREWORD
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International Standard IEC 62317-12 has been prepared IEC technical committee 51: Magnetic
components, ferrite and magnetic powder materials.

This first edition cancels and replaces the first edition of IEC TR 61604 published in 1997. This
edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to IEC TR 61604:
a) amendment of Clause 5 concerning the relationship between standard of European,
Japanese and U.S.A. sizes;
b) addition of Subclause 5.3 concerning coating.

– 4 – IEC 62317-12:2016 © IEC 2016

The text of this standard is based on the following documents:

CDV Report on voting
51/1128/CDV 51/1143/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 the IEC 62317 series, under the general title Ferrite cores – Dimensions, 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• withdrawn,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.
A bilingual version of this publication may be issued at a later date.

FERRITE CORES – DIMENSIONS –
Part 12: Ring cores
1 Scope
This part of IEC 62317 specifies the dimensions that are of importance for mechanical

interchangeability for a preferred range of ring-cores, also called toroid cores, and the effective
parameter values to be used in calculations involving them.
The selection of core sizes for this document is based on the philosophy of including those sizes
which are industrial standards, meaning that they are in broad-based use within industry. See
IEC 62317-1 for more detail concerning the philosophy of selecting core sizes to be included.
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 60205, Calculation of the effective parameters of magnetic piece parts
3 Terms and definitions
No terms and definitions are listed in this document.
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
4 Abbreviated terms
ID    inside diameter
OD outside diameter
5 Primary standards
5.1 General
Compliance with the following requirements ensures mechanical interchangeability of complete
assemblies and wound coils.
5.2 Dimensions of ring-cores
5.2.1 Designation of dimensions
Table 1 describes the alphabetic character assignments for the dimensions of ferrite ring cores.

– 6 – IEC 62317-12:2016 © IEC 2016

Table 1 – Ring core dimension designations

Letter Dimension description
A Outside diameter
B Inside diameter
C Height
5.2.2 Identification of standard sizes

Table 2 shows the nominal dimensions for the range of standard ring cores. Table 2 also shows,

where applicable, the origin and regional name of each standard size, whether from historical
European sizes, historical Japanese sizes, or historical USA sizes. The previous
IEC Technical Report, 61604, detailed the different ring sizes that were tooled and commonly
used in the three distinct geographic regions. IEC TR 61604 laid the groundwork for the present
standard, which reflects the more global nature of the industry, compared with the time when
ferrite standards were evolving in different parts of the world. Manufacturers tend to have more
globally complete offerings of ring sizes than before, leading to a profusion of different sizes.
The number of different ring sizes used in total is quite large, far in excess of the 82 commonly
known standard sizes shown here, for a couple of reasons: ring cores are relatively inexpensive
to build tooling for, nor does a new ring core require an expensive new coil former to be tooled
up, meaning that custom ring cores are often commercially practical. Ferrite rings, lacking a
residual air gap, such as E-cores and other shapes have at their mating surfaces, exhibit
directly the full magnetic performance possible in the ferrite material, meaning that tooling up
precisely optimal new dimensions can give a significant advantage to a designer who is
optimizing for best possible performance.
5.2.3 Effective parameter values
The effective parameter values for the standard ring cores are given in Table 3. For global
practicality and simplicity, the effective parameters in this document are calculated from the
nominal dimensions assuming cores of rectangular cross section, and are useful for reference
and comparison of cores. For cores having a cross section with an appreciable average
rounding radius, more precise values can be calculated from the method given in IEC 60205, if
required.
5.2.4 Dimensio
...