IEC 62317-4:2005

IEC 62317-4 ®
Edition 1.0 2005-09
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Ferrite cores – Dimensions –
Part 4: RM-cores and associated parts

Noyaux ferrites – Dimensions –
Partie 4: Noyaux RM et pièces associées

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IEC 62317-4 ®
Edition 1.0 2005-09
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Ferrite cores – Dimensions –
Part 4: RM-cores and associated parts

Noyaux ferrites – Dimensions –
Partie 4: Noyaux RM et pièces associées

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX S
ICS 29.100.10 ISBN 978-2-88912-594-4

– 2 – 62317-4  IEC:2005
CONTENTS
FOREWORD . 3

1 Scope . 5

2 Normative references. 5

3 Primary standards . 5

3.1 Pin locations and base outlines . 5

3.2 Dimensions of RM-cores . 5

3.3 Shape of coil former and pin numbering . 6

3.4 Effective parameter values . 6
3.5 Spring recess . 6
3.6 Stud recess . 6
4 Derived standards . 10
5 Main dimensions for coil formers . 13
5.1 RM-cores for primary standard . 13
5.2 RM-cores intended particularly for power applications . 15
Annex A (informative) RM-core design . 18
Annex B (normative) Guidance for measuring clamping forces relevant to RM-core tests . 20
Bibliography . 22

Figure 1 – Dimensions of RM-cores . 7
Figure 2 – Dimensions of low-profile RM-cores . 8
Figure 3 – Dimensions of spring recess . 11
Figure 4 – Dimensions of stud recess . 12
Figure 5 – Main dimensions of coil formers for RM-cores . 13
Figure 6 – Pin locations and base outlines viewed from the underside of the board . 14
Figure 7 – Dimensions of specific features . 16
Figure 8 – Pin locations and base outlines viewed from the underside of the board . 17
Figure B.1 – Mounting device . 20

Table 1 – Dimensions of RM-cores . 7
Table 2 – Dimensions of low-profile RM-cores . 8

Table 3 – Effective parameter and A values for RM-cores . 9
min
Table 4 – Effective parameter and A values for low-profile RM-cores . 9
min
Table 5 – Spring recess . 11
Table 6 – Stud recess . 12
Table 7 – Main dimensions of coil formers for RM-cores . 13
Table 8 – Main dimensions of coil formers for low-profile RM-cores . 13
Table 9 – Dimensions of specific features. 16
Table B.1 – Inner diameters and recommended clamping forces . 21

62317-4  IEC:2005 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION

___________
FERRITE CORES – DIMENSIONS –
Part 4: RM-cores and associated parts

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,
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preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with
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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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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 62317-4 has been prepared IEC technical committee 51: Magnetic
components and ferrite materials.

This international standard cancels and replaces the second edition of IEC 60431 published in
1983, its amendment 1 (1995), and its amendment 2 (1996). This international standard
constitutes a technical revision of IEC 60431.
This bilingual version (2011-07) replaces the English version.
The main changes with respect to the previous edition of IEC 60431 are listed below:
– low-profile RM-cores at present defined in IEC 61860 are added to this standard.
IEC 61860 will eventually be replaced by IEC 62317-9 which is under consideration. IEC 62317-9
will not include the low-profile RM-cores.

– 4 – 62317-4  IEC:2005
The text of this standard is based on the following documents:

FDIS Report on voting
51/833/FDIS 51/839/RVD
Full information on the voting for the approval of this standard can be found in the report on voting

indicated in the above table.
The French version of this standard has not been voted upon.

This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
IEC 62317 consists of the following parts, under the general title Ferrite cores – Dimensions:
Part 1: General (under consideration)
Part 2: Pot cores (under consideration, currently available as IEC 60133)
Part 3: Half pot cores (under consideration, currently available as IEC 62323)
Part 4: RM-cores and associated parts
Part 5: EP-cores (under consideration, currently available as IEC 61596)
Part 6: ETD-cores (under consideration, currently available as IEC 61185)
Part 7: EER-cores
Part 8: E-cores
Part 9: Planar cores
Part 10: PM-cores (under consideration, currently available as IEC 61247)
Part 11: EC-cores (under consideration, currently available as IEC 60647)
Part 12: Uncoated ring cores (under consideration, currently available as IEC 61604)
The committee has decided that the contents of this publication will remain unchanged until the
stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data related to the
specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
The contents of the corrigendum of July 2016 have been included in this copy.

62317-4  IEC:2005 – 5 –
FERRITE CORES – DIMENSIONS –
Part 4: RM-cores and associated parts

1 Scope
This part of IEC 62317 specifies the dimensions that are of importance for mechanical

interchangeability for a preferred range of RM-cores and low-profile RM-cores made of ferrite,
and the locations of their terminal pins on a 2,54 mm printed wiring grid in relation to the base
outlines of the cores. It also specifies the test conditions and clamping forces to be used for
inductance measurement.
The general considerations that the design of this range of cores is based upon are given in
Annex A.
2 Normative references
The following referenced documents are indispensable for the application of this document. For
dated references, only the edition cited applies. For undated references, the latest edition of the
referenced document (including any amendments) applies.
IEC 60097:1991, Grid system for printed circuits
IEC 60205:2001, Calculation of the effective parameters of magnetic piece parts
3 Primary standards
Compliance with the following requirements ensures mechanical interchangeability of complete
assemblies and wound coil formers.
3.1 Pin locations and base outlines
These shall be as shown in Figure 6 and Figure 8 (for power applications), in which the base is
viewed from the pin side, i.e. from the underside of the printed wiring boards.
The pins shall fit into holes according to IEC 60097, the nominal hole diameter being:

– 1 mm when the shortest distance between pins is 2,54 mm;
mm or more.
– 1,3 mm when the shortest distance between pins is 2,54 2
3.2 Dimensions of RM-cores
The dimensions of RM-cores shall be as given in Table 1 and the low-profile RM-cores shall be as
given in Table 2.
– 6 – 62317-4  IEC:2005
3.3 Shape of coil former and pin numbering

When the coil former is viewed from the pin side, the pins shall be numbered in a clockwise

direction. Pin 1 shall be a corner pin, or the pin immediately to the right of a corner, and closest to

the base outline.
For asymmetrical arrangements, pin 1 shall be at the side with the largest number of pins. The

coil former shall show an asymmetry which shall preferably be visible (or detectable) when the

assembled inductor is held with the pins downwards. This asymmetry shall clearly indicate pin 1.

For pin numbering of recommended core patterns and for recommended asymmetrical pin

arrangements, see 3.1.
NOTE It is not required that the pin numbers be marked on the coil former.
3.4 Effective parameter values
The effective parameter values for cores having the dimensions given in 3.2 and 3.5 are as shown
in Table 3 and Table 4.
3.5 Spring recess
RM-cores shall have recesses which allow the core halves to be held together by two spring
clamps snapping into these recesses. The recesses consist of a flat spring rest and a locking
ridge. The dimensions are given in Table 5; the profile of this spring recess is not defined but the
limit dimensions shall be complied with.
3.6 Stud recess
Those RM-cores with centerpost holes may have recesses for the fixed part of the adjusting
device with dimensions in accordance with Table 6. These dimensions are not mandatory for
manufacturers who supply cores with the fixed part of the adjusting device attached.

62317-4  IEC:2005                    – 7 –

The dimensions specified in Table 1 are illustrated in Figure 1.
2B
2D
A
A
A
A
M
G
G
G
G
C
C
C
R
C
Type 4
Type 2
Type 3
Type 1
Section X-X
IEC  1475/05
Figure 1 – Dimensions of RM-cores
Table 1 – Dimensions of RM-cores
a)
A B C D E F G H J R
mm mm mm mm mm mm mm mm mm mm
Size Type
Min. Max. Min. Max. Min. Max. Min. Max. Min. Max. Min. Max. Min. Min. Max. Min. Max. Max.
RM 4 10,6 11,8 5,15 5,25 4,40 4,60 3,50 3,70 7,95 8,35 3,70 3,90 5,80 2,0 2,1 9,40 9,80 0,3 3
RM 5 14,0 14,9 5,15 5,25 6,40 6,80 3,15 3,35 10,2 10,6 4,70 4,90 6,00 2,0 2,1 11,8 12,3 0,3 3
RM 6-S 17,2 18,3 6,15 6,25 7,80 8,20 4,00 4,20 12,4 12,9 6,10 6,40 8,40 3,0 3,1 14,1 14,7 0,3 1
RM 6-R 17,2 18,3 6,15 6,25 7,00 7,40 4,00 4,20 12,4 12,9 6,10 6,40 6,30 3,0 3,1 14,1 14,7 0,3 4
RM 7 19,5 20,3 6,65 6,75 6,95 7,25 4,20 4,45 14,75 15,4 6,95 7,25 9,30 3,0 3,1 16,5 17,2 0,3 2
RM 8 22,3 23,2 8,15 8,25 10,6 11,0 5,40 5,65 17,0 17,7 8,25 8,55 9,50 4,4 4,6 18,9 19,7 0,3 3
RM 10 27,2 28,5 9,25 9,35 13,0 13,5 6,20 6,50 21,2 22,1 10,5 10,9 10,9 5,4 5,6 23,6 24,7 0,3 3
RM 12 36,1 37,4 12,2 12,3 15,6 16,1 8,40 8,70 25,0 26,0 12,3 12,8 12,9 - - 28,7 29,8 0,3 3
RM 14 40,8 42,2 14,4 14,5 18,4 19,0 10,4 10,7 29,0 30,2 14,4 15,0 17,0 5,4 5,6 33,5 34,7 0,3 3
RM 14A 40,8 42,2 15,0 15,1 18,4 19,0 10,4 10,7 29,0 30,2 14,4 15,0 17,0 - - 33,5 34,7 0,3 3
a)
Solid centerpost cores are available for each size.
J
J
J
J
H
F
E
– 8 –                  62317-4  IEC:2005

The dimensions specified in Table 2 are illustrated in Figure 2.
2B
2D
A
A
A
G
G G
C
C C
R
Type 2
Type 1
Section X-X
Type 3
IEC  1476/05
Figure 2 – Dimensions of low-profile RM-cores
Table 2 – Dimensions of low-profile RM-cores
a)
A B C D E F G H J R
mm mm mm mm mm mm mm mm mm mm
Size Type
Min. Max. Min. Max. Min. Max. Min. Max. Min. Max. Min. Max. Min. Min. Max. Min. Max. Max.
RM 4/8 10,6 11,8 3,80 3,90 4,40 4,60 2,15 2,35 7,95 8,35 3,70 3,90 5,8 2,0 2,1 9,40 9,80 0,3 3
RM 5/8 14,0 14,9 3,80 3,90 6,40 6,80 1,80 2,00 10,2 10,6 4,70 4,90 6,0 2,0 2,1 11,8 12,3 0,3 3
RM 6/9 17,2 18,3 4,40 4,50 7,80 8,20 2,25 2,45 12,4 12,9 6,10 6,40 8,4 3,0 3,1 14,1 14,7 0,3 1
RM 7/10 19,5 20,3 4,80 4,90 6,95 7,25 2,35 2,60 14,75 15,4 6,95 7,25 9,3 3,0 3,1 16,5 17,2 0,3 2
RM 8/11 22,3 23,2 5,70 5,80 10,6 11,0 2,95 3,15 17,0 17,7 8,25 8,55 9,5 4,4 4,6 18,9 19,7 0,3 3
RM 10/13 27,2 28,5 6,40 6,50 13,0 13,5 3,35 3,55 21,2 22,1 10,5 10,9 10,9 5,4 5,6 23,6 24,7 0,3 3
RM 12/17 36,1 37,4 8,30 8,40 15,6 16,1 4,50 4,75 25,0 26,0 12,3 12,8 12,9 5,4 5,6 28,7 29,8 0,3 3
RM 14/20 40,8 42,2 10,15 10,25 18,4 19,0 5,55 5,85 29,0 30,2 14,4 15,0 17,0 5,4 5,6 33,5 34,7 0,3 3
a)
Solid centerpost cores are available for each size.

J
J
J
H
F
E
62317-4  IEC:2005 – 9 –
Table 3 – Effective parameter and A values for RM-cores
min
a)
with hole O C C l A V A
1 2 e e e min
Size
–1 –3 2 3 2
no hole  Ø mm mm mm mm mm mm

–3
1,889 4 20,7   10,9   226    8,04
O 172,74 × 10
RM 4
–3
Ø 1,633 0 116,54 × 10 22,9   14,0   321   11,3

–3
O 1,021 0 20,9   20,5   430   14,8
49,866 × 10
RM 5
–3
Ø 0,943 15 39,774 × 10 22,4   23,7   530   18,1

–3
O 0,897 83 27,2   30,3   830   23,4
29,592 × 10
RM 6-S
–3
0,816 68 28,9   35,4  1 020   30,7
Ø 23,099 × 10
–3
O 0,821 49 25,728 × 10 25,7   31,3   810   23,4
RM 6-R
–3
Ø  0,740 34 27,8   37,5  1 040   30,7
19,737 × 10
–3
O 0,720 27 17,389 × 10 29,8   41,4  1 240   32,3
RM 7
–3
Ø  0,672 53 31,2   46,4  1 450   39,6
14,509 × 10
–3
0,685 47 35,5   51,8  1 840   40,0
O 13,238 × 10
RM 8
–3
Ø  0,607 35 9,650 5 × 10 38,2   62,9  2 410   55,0
–3
O 0,504 94 42,3   83,9  3 550   66,0
6,021 9 × 10
RM 10
–3
Ø  0,455 90 4,634 7 × 10 44,8   98,4  4 410   90,0
–3
RM 12 Ø  0,384 35 56,3 147  8 250 125
2,623 1 × 10
–3
0,382 77 67,0 175 11 700 146
O 2,185 7 × 10
RM 14
–3
Ø  0,363 24 1,916 8 × 10 68,8 189 13 000 170
–3
RM 14A Ø  0,351 03 69,7 199 13 900 170
1,766 7 × 10
a)
See 2.2 of IEC 60205 for the definition of A .
min
NOTE The manufacturers may indicate in their catalogues more precise values than those given in the above table.

Table 4 – Effective parameter and A values for low-profile RM-cores
min
a)
with hole O C C l A V A
1 2 e e e min
Size
–1 –3 2 3 2
no hole  Ø mm mm mm mm mm mm
–3
O 1,363 7 15,8 11,6  182    8,04
117,98 × 10
RM 4/8
–3
1,205 0 17,6 14,6   257  11,3
Ø 82,549 × 10
–3
O 0,748 38 34,487 × 10 16,2 21,7   352  14,8
RM 5/8
–3
Ø 0,703 79 17,4 24,7   430  18,1
28,484 × 10
–3
O 0,656 34 20,781 × 10 20,7 31,6   655  23,4
RM 6/9
–3
Ø 0,610 85 22,0 36,0   791  31,2
16,976 × 10
–3
0,528 24 22,8 43,2   987  32,3
O 12,220 × 10
RM 7/10
–3
Ø 0,501 64 10,529 × 10 23,9 47,6  1 140   39,6
–3
O 0,479 06 26,3 54,9  1 440   39,5
8,726 5 × 10
RM 8/11
–3
Ø 0,436 89 6,699 3 × 10 28,5 65,2  1 860   55,4
–3
O 0,359 49 31,4 87,5  2 750   66,2
4,109 9 × 10
RM 10/13
–3
0,333 60 33,4  100  3 340   89,9
Ø 3,331 6 × 10
–3
O 0,295 78 2,227 5 × 10 39,3  133  5 220   99,9
RM 12/17
–3
Ø 0,279 06 41,3  148  6 120 125
1,883 9 × 10
–3
O 0,263 67 1,409 7 × 10 49,3  187  9 920 146
RM 14/20
–3
Ø 0,253 40 50,9  201 10 200 170
1,261 1 × 10
a)
See 2.2 of IEC 60205 for the definition of A
min.
NOTE The manufacturers may indicate in their catalogues more precise values than those given in the above table.

– 10 – 62317-4  IEC:2005
4 Derived standards
Parties interested in making or using RM-cores may find it desirable to lay down local standards

for everyday use. These may show the dimensions in greater detail than Clause 3, and may

correspond to the state of art in that area. When doing so, care should be taken not to exclude any

other type of RM-core which meets the IEC primary standard and which also meets the

requirements of the user.
When a national standard is prepared, the relevant national standardization body is strongly

requested to insert a note stating that:

a) the standard is in accordance with the dimensional standard of this part of IEC 62317 but that
more details are given in order to promote the practical use of the standard;
b) other solutions are possible within the framework of this part of IEC 62317 and should not be
excluded if such cores and formers are functionally interchangeable with those according to
the national standard.
62317-4  IEC:2005 – 11 –
The dimensions specified in Table 5 are illustrated in Figure 3.

G
G
m 1
IEC  1477/05
Figure 3 – Dimensions of spring recess
Table 5 – Spring recess
a)b) a)c) a)d)
H H G G m
3 4 1 2
mm mm mm mm mm
Size
Min. Max. Min. Max. Max. Min. Min.
RM 4   8,75  9,25 0,05 0,15 1,0 1,65 2,5
RM 5   8,75  9,25 0,05 0,15 1,0 1,65 2,5
RM 6  10,09 10,59 0,10 0,20 1,3 2,2 2,5
RM 7  11,09 11,59 0,10 0,20 1,3 2,2 3,3

RM 8  14,05 14,55 0,10 0,20 1,3 2,2 5,0
RM 10  15,95 16,45 0,15 0,25 1,3 2,25 5,0
RM 12 21,4 21,9 0,15 0,25 1,3 3,5 5,0
RM 14  25,55  26,05 0,15 0,25 1,3 3,6 5,6
RM 14A 26,8 27,3 0,15 0,25 1,3 3,6 5,6
a)
Dimensions G and G define the boundaries of the flat spring rest.
1 2
b)
In particular cases, the design of the spring may require the tolerance on H to be smaller.
c)
The form of the locking ridge is not prescribed but it shall be essentially uniform over the width m in order not to
hinder the correct application of the spring. The outer side may be of any form facilitating the introduction of the
spring into the recess; the inner side may be of any form but shall not protrude through a flat plane making an angle
of 120° with the flat spring rest and containing its boundary defined by dimensions G .
d)
The inner side of the spring recess may be of any form but it shall not protrude through a flat plane making an angle
of 120° with the flat spring rest and containing its boundary defined by dimension G .
H
H
H
– 12 – 62317-4  IEC:2005
The dimensions specified in Table 6 are illustrated in Figure 4.

d
IEC  1478/05
Figure 4 – Dimensions of stud recess
Table 6 – Stud recess
d t
Size mm mm
Min. Min. Max.
RM 4 3,0 0,4 0,7
RM 5 3,0 0,4 0,7
RM 6 4,3 0,7 1,0
RM 7 4,3 0,7 1,0
RM 8 6,0 0,7 1,0
RM 10 7,6 0,8 1,1
RM 14 7,6 0,8 1,1
t
62317-4  IEC:2005 – 13 –
5 Main dimensions for coil formers

5.1 RM-cores for primary standard

The dimensions specified in Tables 7 and 8 are illustrated in Figure 5.

H H
5 4
L
H
IEC  1479/05
Figure 5 – Main dimensions of coil formers for RM-cores
Table 7 – Main dimensions of coil formers for RM-cores
D D D H H H L d
1 2 3 2 4 5
Size mm mm mm mm mm mm mm mm
Min. Max. Min. Max. Min. Max. Min. Max. Max. Max. Min. Min. Max.
RM 4 7,65 7,85 4,75 4,95 4,00 4,15 6,65 6,85 0,80 0,50 3,90 0,50 0,60
RM 5 9,90 10,1 5,75 5,95 5,00 5,15 5,95 6,15 0,80 0,55 4,50 0,50 0,60
RM6-R 12,1 12,3 7,20 7,30 6,50 6,60 7,70 7,85 0,80 0,55 4,80 0,58 0,62
RM6-S 12,1 12,3 7,25 7,45 6,50 6,60 7,70 7,85 0,90 0,55 4,30 0,50 0,60
RM 7 14,4 14,66 8,00 8,30 7,30 7,60 8,10 8,25 0,80 0,55 6,6 0,78 0,82
RM 8 16,7 16,9 9,75 9,95 8,70 8,90 10,4 10,65 1,05 0,65 5,00 0,60 0,70
RM 10 20,8 21,0 12,3 12,50 11,1 11,3 12,0 12,25 1,05 0,70 5,35 0,60 0,70
RM 12 24,5 24,7 14,2 14,5 13,0 13,3 16,25 16,5 1,05 0,75 6,00 0,75 0,85

RM 14 28,6 28,8 16,6 16,80 15,2 15,4 20,2 20,5 1,05 0,85 6,10 0,75 0,85

Table 8 – Main dimensions of coil formers for low-profile RM-cores
D D D H H H L d
1 2 3 2 4 5
Size mm mm mm mm mm mm mm mm
Min. Max. Min. Max. Min. Max. Min. Max. Max. Max. Min. Min. Max.
RM 4/8 7,65 7,85 4,75 4,95 4,00 4,15 4,05 4,20 0,80 0,50 3,90 0,50 0,60
RM 5/8 9,90 10,1 5,75 5,95 5,00 5,15 3,35 3,50 0,80 0,55 4,50 0,50 0,60
RM 6/9 12,1 12,3 7,20 7,30 6,50 6,60 4,25 4,40 0,90 0,55 4,80 0,58 0,62
RM 7/10 14,4 14,66 8,00 8,30 7,30 7,60 4,45 4,60 0,80 0,55 6,60 0,78 0,82
RM 8/11 16,70 16,9 9,75 9,95 8,70 8,90 5,55 5,70 1,05 0,65 5,00 0,60 0,70
RM10/13 20,8 21,0 12,3 12,5 11,1 11,3 6,35 6,50 1,05 0,70 5,35 0,60 0,70
RM12/17 24,5 24,7 14,2 14,5 13,0 13,3 8,65 8,80 1,05 0,75 6,00 0,75 0,85
RM14/20 28,6 28,8 16,6 16,8 15,2 15,4 10,75 10,9 1,05 0,85 6,10 0,75 0,85
D
D
D
d
– 14 – 62317-4  IEC:2005
Earth pin
1 1 2
Earth pin
(2×)
6 6 (2×)
5 4
Earth pin
(2×)
RM 5 RM 6
RM 4
Earth pin 1
1 3
Earth pin
(2×)
(2×)
RM 7 with 5 pins RM 7 with 8 pins

1 2 1
Earth pin
12 12 3
Earth pin Earth pin
(2×)
(2×) (2×)
6 8
RM 8 with 8 pins at 2,54     2 mm
RM 8 with 8 pins at 2,54 mm RM 8 with 12 pins

1 2
Earth pin 4
7 5
(2×)
9 6
Earth pin
8 7
(2×)
RM 10 RM 12
IEC  1480/05
Figure 6 – Pin locations and base outlines viewed from the underside of the board

62317-4  IEC:2005 – 15 –
Earth pin
(4×)
RM 14 IEC  1481/05
Figure 6 – Pin locations and base outlines viewed from the underside of the board
(continued)
NOTE To obtain an asymmetrical arrangement, one pin may be omitted on one side from a symmetrical arrangement.
For RM 7, the 5-pin version has an asymmetrical arrangement.
For the other cores, omit:
- for RM 4, RM 5 and RM 6 with 5 pins: No. 4 pin;
- for RM 8 with 11 pins: No. 6 pin;
- for RM 10 with 11 pins: No. 9 pin;
- for RM 12 with 11 pins: No. 10 pin;
- for RM 14 with 10 pins: No. 5 and No. 8 pins.
5.2 RM-cores intended particularly for power applications
These coil formers are intended for use with cores RM 6-S, RM 8, RM 10, RM 12 and RM 14A, all
without centre holes. Each is provided with 12 terminal pins except for the RM 6-S coil former,
which has only eight.
Figure 7 shows the features specific to this format and the corresponding dimensions are given in
Table 9.
– 16 – 62317-4  IEC:2005
D
Marking for pin 1
b
max
D
p
IEC  1482/05
Figure 7 – Dimensions of specific features
Table 9 – Dimensions of specific features
D D D H H H
1 2 3 2 4 5
mm mm mm mm mm mm
Size
Min. Max. Min. Max. Min. Max. Min. Max. Max. Max.
RM 6-S 12,1 12,3  7,25  7,45  6,50  6,60  7,70  7,95 1,05 0,60
RM 8 16,7 16,9  9,75  9,95  8,70  8,90 10,4 10,65 1,20 0,75
RM 10 20,8 21,0 12,3 12,5 11,1 11,3 12,0 12,25 1,30 0,80
RM 12 24,5 24,7 14,2 14,5 13,0 13,3 16,25 16,5 1,30 0,80

RM 14A 28,6 28,8 16,6 16,8 15,2 15,4 20,2 20,5 1,40 0,90

a b c d e p q
max. max.
Size
mm mm mm mm mm mm mm
RM 6-S 16,0 24,9 2,2 2,6 0,3 0,63 3,8
RM 8 23,5 29,9 2,5 3,1 0,3 0,63 3,8
RM 10 23,3 39,4 3,1 3,45 0,3 1,0 3,8
RM 12 28,4 45,2 3,2 3,7 0,3 1,0 4,2
RM 14A 31,4 48,4 4,0 4,4 0,3 1,0 4,2

D
H
H
c
H
a
e
q
max
d
62317-4  IEC:2005 – 17 –
RM 6-S
+0,1
Earth points RM 12
+0,1
Earth points
∅1
0 ∅1,3
No.1
No.8
No.12
No.1
No.5
+0,15
+0,15
∅1,6
∅1
6 × 2,54 = 15,24
No.4
No.7
Earth points
No.6
RM 8
+0,1
∅1,3
No.1
No.12
13 × 2,54 = 33,02
Earth points
RM 14A
+0,1
7,62
∅1,3
No.12
No.1
+0,15
∅1
No.7  0
8 × 2,54 = 20,32
No.6
+0,15
RM 10
Earth points +0,1
∅1,6
∅1,3  0
No.12
No.1
No.6
No.7
14 × 2,54 = 35,56
+0,15
∅1
No.6
No.7
11 × 2,54 = 27,94
IEC  1483/05
Figure 8 – Pin locations and base outlines viewed from the underside of the board
8 × 2,54 = 20,32
8 × 2,54 = 20,32
5 × 2,54 = 12,7
3,81 3,81
5,08
3,81
5,08
5,08
7 × 2,54 = 17,78
10 × 2,54 = 25,4
5 × 5,08 = 25,4
11 × 2,54 = 27,94
– 18 – 62317-4  IEC:2005
Annex A
(informative)
RM-core design
A.1 General
The design of RM-cores standardized by the IEC is based on the following considerations:

a) RM-cores are especially suited for use on printed wiring boards, because it is possible to
solder the wire leads of the coils directly to the pin terminations moulded in the coil former.
Normally, these pins should remain within the outline of the core base.
b) RM-cores are primarily used for inductors and tuned transformers, but they can also be used
for broad-band transformers and in switched mode power supply applications.
For RM-cores which are used for fixed inductors and untuned transformers, where the
adjuster hole is unnecessary, a solid centre pole (no hole) construction may be used. This
gives a higher effective permeability and, in particular, more efficient operation than the
corresponding cores with a hole, an important consideration for power applications.
Cores up to and including RM 10 are specified for both forms of construction, whilst RM 12
and RM 14A are specifically intended for applications requiring a solid centre pole.
The counterpart to RM 14, with an adjuster hole, is a taller core RM 14A with solid centre pole,
whose essential advantage is a thicker base, to permit greater values of A and A to be
e min
achieved, while enabling the ratio A /A to be maintained almost unchanged.
e min
c) The base areas are square with cut-outs for the terminal pins in two opposite corners. The
winding space is annular.
A.2 Pin locations and base outlines
In order to provide for the largest possible number of pins, the shortest distance between pin
centres of 2,54 mm should be chosen. This can be safely handled by modern soldering
techniques for miniature printed wiring. The result is a maximum of 6 pins on the smallest cores
(e.g. base dimensions 10 mm × 10 mm) and up to 12 pins for a large core (base dimensions
20 mm × 20 mm). If the maximum number of pins is not required, the shortest distance between
pin centres can be increased to 2,54 2 mm by omitting certain pins.
When the pins are placed on the primary grid, the sides of the core base are located at half grid
spacing (except for RM 10). This allows the neighbouring pins of adjacent cores when placed side

by side to be located on parallel grid lines which are 2,54 mm apart.
A.3 Design considerations and dimensions
The range of base sizes is compatible with 4, 5, 6, 7, 8, 10 and 14 printed wiring modules of
2,54 mm.
Further aspects of the design are:
– a maximum wall height to thickness ratio of 5:1;
– a thickness of the core base sufficient to accommodate the wires terminated on the pins of the
coil former;
– an adjuster hole diameter in accordance with IEC 60133.

62317-4  IEC:2005 – 19 –
Within these limitations, and assuming acceptable core heights and reasonable cut-out

dimensions, the optimum inner and outer diameters of the winding space can be calculated with

regard to the qualities R /L and hysteresis loss.
dc
For this calculation, currently used wall thicknesses for the coil formers have been taken into

account, for example for RM 6 a flange thickness of approximately 0,5 mm and a cylinder wall

thickness of approximately 0,3 mm. The effect of cut-outs on the optimum dimensions of a core

may be considerable; the calculation has been based on cut-outs which suit most practical

applications.
A.4 Practical considerations
The cut-outs should preferably reach the centre boss so that the inner terminating wire can easily
be led out.
In order to obtain adequate adjuster performance, the tightened tolerance on the centre hole in
accordance with IEC 60133 should be used. For some sizes like RM 5, the adjuster performance
may still be inadequate and a further tightening of the tolerance should then be considered by the
manufacturer.
– 20 – 62317-4  IEC:2005
Annex B
(normative)
Guidance for measuring clamping forces

relevant to RM-core tests
B.1 Test conditions and clamping forces

In order to ensure a good repeatability of the measurements, specially on A values with or
L
without air-gaps, the clamping forces and the relevant clamping procedure are specified.
B.2 Clamping procedure
For every electrical test, the core set should be assembled with the appropriate measuring coil.
During the measurements, a specified clamping force is applied in order to limit the parasitic
air-gap and ensure a good contact between the mating surfaces.

∅D
i
F
Ferrite core
Mating surface
Measuring coil
∅D
i
IEC  1484/05
Figure B.1 – Mounting device
Table B.1 gives the typical inner diameters D for the design of mounting devices, as illustrated in
i
Figure B.1, and gives the recommended minimum and maximum clamping forces to be applied
during the different electrical tests for each RM-core type.

62317-4  IEC:2005 – 21 –
Table B.1 – Inner diameters and recommended clamping forces

Inner diameter Clamping force
D F
i
Size
mm N
Typical Min. Max.
RM 4 8 10 15
RM 5 10 15 25
RM 6 12 25 35
RM 7 15 30 40
RM 8 17 45 55
RM 10 21 45 55
RM 12 25 45 55
RM 14 29 45 55
NOTE For measurement of tanδ, hysteresis constant, and THD , the measurements are sensitive to mechanical
F
stress, and reduced clamping pressures are recommended, 0,2 N/mm , with a relative tolerance of ± 10 %, with force
applied only in a direction perpendicular to the mating surface.

– 22 – 62317-4  IEC:2005
Bibliography
IEC 60133:2000, Dimensions of pot-cores made of magnetic oxides and associated parts

___________
– 24 – 62317-4  CEI:2005
SOMMAIRE
AVANT-PROPOS . 25

1 Domaine d’application . 27

2 Références normatives . 27

3 Normes principales . 27

3.1 Emplacement des broches et périmètre d'embase . 27

3.2 Dimensions des noyaux RM . 27

3.3 Forme de la carcasse et numérotage des broches . 28

3.4 Valeurs des paramètres effectifs . 28
3.5 Encoche pour la bride-ressort . 28
3.6 Encoche pour la pièce filetée . 28
4 Normes dérivées . 32
5 Dimensions principales pour les carcasses . 34
5.1 Noyaux RM pour Norme principale . 34
5.2 Noyaux RM utilisés plus particulièrement dans les applications de puissance . 37
Annexe A (informative) Conception des noyaux RM . 40
Annexe B (normative) Guide pour la mesure des forces d'assemblage relatives aux
essais sur les noyaux RM . 42
Bibliographie . 44

Figure 1 – Dimensions des noyaux RM . 29
Figure 2 – Dimensions des noyaux RM faible hauteur . 30
Figure 3 – Dimensions de l'encoche pour la bride-ressort . 33
Figure 4 – Dimensions de l'encoche pour la pièce filetée . 34
Figure 5 – Dimensions principales des carcasses pour les noyaux RM . 35
Figure 6 – Emplacement des broches et périmètre d'embase vus depuis la face inférieure
de la carte . 36
Figure 7 – Dimensions des caractéristiques spécifiques . 38
Figure 8 – Emplacement des broches et périmètre d'embase vus depuis la face inférieure
de la carte . 39
Figure B.1 – Dispositif d'assemblage . 42

Tableau 1 – Dimensions des noyaux RM . 29
Tableau 2 – Dimensions des noyaux RM faible hauteur . 30
Tableau 3 – Valeurs des paramètres effectifs et A pour noyaux RM . 31
min
Tableau 4 – Valeurs des paramètres effectifs et A pour noyaux RM faible hauteur . 31
min
Tableau 5 – Encoche pour la bride-ressort . 33
Tableau 6 – Encoche pour la pièce filetée . 34
Tableau 7 – Dimensions principales des carcasses pour les noyaux RM . 35
Tableau 8 – Dimensions principales des carcasses pour les noyaux RM faible hauteur . 35
Tableau 9 – Dimensions des caractéristiques spécifiques . 38
Tableau B.1 – Diamètres intérieurs et forces d'assemblage recommandées . 43

62317-4  CEI:2005 – 25 –
COMMISSION ÉLECTROTECHNIQUE INTERNATIONALE

___________
NOYAUX FERRITES – DIMENSIONS –

Partie 4: Noyaux RM e
...