IEC 63093-9:2026

IEC 63093-9 ®
Edition 2.0 2026-02
INTERNATIONAL
STANDARD
REDLINE VERSION
Ferrite cores - Guidelines on dimensions and the limits of surface irregularities -
Part 9: Planar cores
ICS 29.100.10 ISBN 978-2-8327-1066-1
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CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Primary dimensions . 6
4.1 Planar shapes and dimensions . 6
4.2 Dimensions and effective parameters of planar EL-core and mating PLT-
core . 7
4.3 Dimensions and effective parameters of low-profile E-core and mating PLT-
core . 10
4.4 Dimensions and effective parameters of low-profile ER-core and mating
PLT-core . 12
5 Limits of surface irregularities . 15
5.1 General . 15
5.2 Examples of surface irregularities . 16
5.3 Chips and ragged edges . 16
5.3.1 General . 16
5.3.2 Chips and ragged edges on the mating surfaces . 17
5.3.3 Chips and ragged edges on other surfaces . 18
5.4 Cracks . 20
5.5 Flash . 20
5.6 Pull-outs . 20
5.7 Crystallites . 23
5.8 Pores . 24
Annex A (normativeinformative) Low-profile core design . 26
A.1 General design . 26
A.2 EL-core design. 26
A.3 ER-core design . 27
Annex B (informative) Reference values of allowable areas of chips . 29
Bibliography . 31

Figure 1 – Planar EL-core and mating PLT-core . 7
Figure 2 – Low-profile E-core and mating PLT-core . 10
Figure 3 – Low-profile ER-core and mating PLT-core . 12
Figure 4 – Examples of surface irregularities for planar EL-core . 15
Figure 5 – Examples of surface irregularities for low-profile E-core . 15
Figure 6 – Examples of surface irregularities for low-profile ER-core . 16
Figure 7 – Chip location for planar EL-core . 16
Figure 8 – Chip location for low-profile E-core . 16
Figure 9 – Chip location for low-profile ER-core . 17
Figure 10 – Cracks and pull-out location for planar EL-core . 19
Figure 11 – Cracks and pull-out location for low-profile E-core . 20
Figure 12 – Cracks and pull-out location for low-profile ER-core . 20
Figure 13 – Reference dimensions for EL-core . 20
Figure 14 – Reference dimensions for E-core . 21
Figure 15 – Reference dimensions for ER-core . 22
Figure 16 – Example of the location of a crystallite on planar EL-core . 23
Figure 17 – Example of the location of a crystallite on low-profile E-core . 23
Figure 18 – Example of the location of a crystallite on low-profile ER-core . 23
Figure 19 – Example of the location of a pore on planar EL-core . 24
Figure 20 – Example of the location of a pore on low-profile E-core . 24
Figure 21 – Example of the location of a pore on low-profile ER-core. 24

Table 1 – Dimensions of planar EL-core EL and mating PLT-core . 8
Table 2 – Effective parameter values and A values. 9
min
Table 3 – Dimensions of low-profile E-core and mating PLT-core . 10
Table 4 – Effective parameter values and A values. 11
min
Table 5 – Dimensions of low-profile ER-core and mating PLT-core . 12
Table 6 – Effective parameter values and A values. 14
min
Table 7 – Area and length reference for visual inspection . 18
Table 8 – Limits of cracks for planar EL-core . 21
Table 9 – Limits of cracks for low-profile E-core . 21
Table 10 – Limits of cracks for low-profile ER-core . 22
Table A.1 – Sizes and design ratios for ER-core . 27
Table B.1 – Allowable areas of chips for planar EL-core . 28
Table B.2 – Allowable areas of chips for low-profile E-core . 28
Table B.3 – Allowable areas of chips for low-profile ER-core . 29

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
Ferrite cores -
Guidelines on dimensions and the limits of surface irregularities -
Part 9: Planar cores
FOREWORD
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This redline version of the official IEC Standard allows the user to identify the changes made
to the previous edition IEC 63093-9:2020. A vertical bar appears in the margin wherever a
change has been made. Additions are in green text, deletions are in strikethrough red text.

IEC 63093-9 has been prepared by IEC technical committee 51: Magnetic components, ferrite
and magnetic powder materials. It is an International Standard.
This second edition cancels and replaces the first edition published in 2020. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) correction of some numbers in Table 2;
b) amendment of Table 6 following IEC 60205.
The text of this International Standard is based on the following documents:
Draft Report on voting
51/1587/FDIS 51/1600/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
A list of all parts in the IEC 63211 series, published under the general title Ferrite cores -
guidelines on dimensions and the limits of surface irregularities, 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 webstore.iec.ch in the data related to the
specific document. At this date, the document will be
– reconfirmed,
– withdrawn, or
– revised.
INTRODUCTION
Today, DC-to-DC converter power supplies increasingly employ transformers and chokes, the
windings of which are made of multi-layer printed circuit boards or are constructed in the
motherboard, rather than the transformers wound by conventional copper wires. This document
specifies the optimum shapes and dimensions of cores for surface mounted devices (SMDs)
and of cores for which the windings are constructed in the motherboard. The motherboard has
slots cut out to accept the ferrite cores. This is called the total integration in a multi-layer
motherboard. The core shape specified in this document satisfies the demand for lower profile
as well as for smaller floor space.
The relations between the main dimensions of planar E-, ER- and EL-cores differ from those of
standard cores. For example, the width of planar cores is larger while the total height is much
smaller. Also, the thickness of the legs is in most cases smaller than compared to standard
cores. Therefore, the concept of fixed reference dimensions to determine the length of crack
limits yields crack lengths which are not acceptable for this type of core. This document follows
another concept which relates the crack length to dimensions of the surface on which the crack
occurs.
Also, the concept to determine the maximum area of chips based on the total mating surface
fails in the case of planar cores. The outer legs of planar cores are much thinner than those of
standard cores which makes overlapping and gluing much more difficult. A single chip of
maximum size on the outer leg can affect the functionality of the core set. Therefore, this
document uses as a reference the mating surface on which the chip occurs.
Windings of planar cores are often PCBs which are glued to the inner surfaces of the planar
core. For this reason, it is important that the inner surfaces of the planar cores should have a
better quality than the inner surfaces of standard cores. This was taken into account by reducing
the maximum allowable area of pull-outs in the inner surfaces.

1 Scope
This part of IEC 63093 specifies the shapes and dimensions of ferrite cores for inductive
components (transformers and chokes), whose the coil is typically made of multi-layer boards
(or the coil is part of the motherboard), and the effective parameter values used in calculations
designed to employ coils that are made of multi-layer boards, or coils that are part of the
motherboard, or flat conductor coils that are helically wound. This part also gives the effective
parameter values used in magnetic calculations for such planar cores. In addition, this
document gives guidelines on allowable limits of surface irregularities applicable to for planar-
cores as well.
This document is considered as a sectional specification useful in the negotiation between
ferrite core suppliers and users about surface irregularities.
The general consideration upon which the design of this range of cores is based is given in
Annex A.
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 60205:2016, Calculation of the effective parameters of magnetic piece parts
IEC 60401-1, Terms and nomenclature for cores made of magnetically soft ferrites - Part 1:
Terms used for physical irregularities and reference of dimensions
IEC 60424-1, Ferrite cores – Guidelines on the limits of surface irregularities – Part 1: General
specification
IEC 63093-1, Ferrite cores - Guidelines on dimensions and the limits of surface irregularities -
Part 1: General specification
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60401-1 and
IEC 60424-1 IEC 63093-1 apply.
ISO and IEC maintain terminology databases for use in standardization at the following
addresses:
– IEC Electropedia: available at https://www.electropedia.org/
– ISO Online browsing platform: available at https://www.iso.org/obp
4 Primary dimensions
4.1 Planar shapes and dimensions
The main shapes and dimensions shall be as given in the following figures and tables.
The main shapes, dimensions, and parameters for EL-cores are given in:
– Figure 1 – Planar EL-core- and mating PLT-core;
– Table 1 – Dimensions of planar EL-core and mating PLT-core;
– Table 2 – Effective parameter values and A values.
min
The main shape, dimensions, and parameters for low-profile E-cores are given in:
– Figure 2 – Low-profile E-core and mating PLT-core;
– Table 3 – Dimensions of low-profile E-core and mating PLT-core;
– Table 4 – Effective parameter values and A values.
min
The main shape, dimensions, and parameters for ER-cores are given in:
– Figure 3 – Low-profile ER-core and mating PLT-core;
– Table 5 – Dimensions of low-profile ER-core and mating PLT-core;
values.
– Table 6 – Effective parameter values and A
min
A uniform dimensional nomenclature has been chosen in order to facilitate a comparison of
major physical attributes among the different core shapes.
4.2 Dimensions and effective parameters of planar EL-core and mating PLT-core
For the definitions of effective parameters and their calculations, reference shall be made to
IEC 60205.
Figure 1 – Planar EL-core and mating PLT-core
Table 1 – Dimensions of planar EL-core EL and mating PLT-core
Size B B F F R
A C D E
1 2 1 2 2
EL11 × 2,0 Min. 10,80 1,91 8,60 0,90 8,97 2,68 6,25 0,3
Max. 11,20 2,11 9,00 1,10 9,37 2,88 6,55
EL11 × 3,0 Min. 10,80 2,91 8,60 1,90 8,97 2,68 6,25 0,3
Max. 11,20 3,11 9,00 2,10 9,37 2,88 6,55
PLT11 × 1,0 Min. 10,80 0,96 8,60
Max. 11,20 1,06 9,00
EL13 × 2,2 Min. 12,75 2,09 10,20 0,90 10,63 3,19 7,41 0,3
Max. 13,25 2,29 10,60 1,10 11,03 3,39 7,71
EL13 × 3,2 Min. 12,75 3,09 10,20 1,90 10,63 3,19 7,41 0,3
Max. 13,25 3,29 10,60 2,10 11,03 3,39 7,71
PLT13 × 1,2 Min. 12,75 1,14 10,20
Max. 13,25 1,24 10,60
EL15,5 × 2,9 Min. 15,20 2,82 12,15 1,40 12,67 3,82 8,81 0,3
Max. 15,80 3,02 12,65 1,60 13,17 4,02 9,21
EL15,5 × 4,4 Min. 15,20 4,32 12,15 2,90 12,67 3,82 8,81 0,3
Max. 15,80 4,52 12,65 3,10 13,17 4,02 9,21
PLT15,5 × 1,4 Min. 15,20 1,32 12,15
Max. 15,80 1,52 12,65
EL18 × 3,7 Min. 17,70 3,55 14,15 1,90 14,70 4,45 10,27 0,3
Max. 18,30 3,75 14,65 2,10 15,30 4,65 10,67
EL18 × 5,7 Min. 17,70 5,55 14,15 3,85 14,70 4,45 10,27 0,3
Max. 18,30 5,75 14,65 4,15 15,30 4,65 10,67
PLT18 × 1,7 Min. 17,70 1,55 14,15
Max. 18,30 1,75 14,65
EL20 × 3,8 Min. 19,65 3,73 15,70 1,90 16,37 4,91 11,43 0,5
Max. 20,35 3,93 16,30 2,10 16,97 5,21 11,83
EL20 × 5,8 Min. 19,65 5,68 15,70 3,85 16,37 4,91 11,43 0,5
Max. 20,35 5,98 16,30 4,15 16,97 5,21 11,83
PLT20 × 1,8 Min. 19,65 1,73 15,70
Max. 20,35 1,93 16,30
EL22 × 4,0 Min. 21,60 3,92 17,30 1,90 17,98 5,41 12,54 0,5
Max. 22,40 4,12 17,90 2,10 18,68 5,71 13,04
EL22 × 6,0 Min. 21,60 5,87 17,30 3,85 17,98 5,41 12,54 0,5
Max. 22,40 6,17 17,90 4,15 18,68 5,71 13,04
PLT22 × 2,0 Min. 21,60 1,92 17,30
Max. 22,40 2,12 17,90
EL25 × 4,3 Min. 24,55 4,19 19,65 1,90 20,48 6,17 14,29 0,5
Max. 25,45 4,39 20,35 2,10 21,18 6,47 14,79
EL25 × 6,3 Min. 24,55 6,14 19,65 3,85 20,48 6,17 14,29 0,5
Max. 25,45 6,44 20,35 4,15 21,18 6,47 14,79
PLT25 × 2,3 Min. 24,55 2,19 19,65
Max. 25,45 2,39 20,35
NOTE All dimensions are expressed in millimetres.

Table 2 – Effective parameter values and A values
min
a
C C l A V
Size A Remarks
1 2 e e e min
–1 –3 2 3 2
mm
mm mm mm mm mm
–3
The
EL-EL11 × 4,0 0,826 45 49,923 × 10 13,7 16,5 226 15,9
combination
–3
EL-EL13 × 4,4 0,666 66 28,815 × 10 15,4 23,1 357 22,4
EL-EL refers
to two shorter
–3
EL-EL15,5 × 5,8 0,596 74 18,143 × 10 19,6 32,9 646 31,9
height EL-
cores for
–3
EL-EL18 × 7,3 0,538 30 23,8 44,3 1 050 43,0
12,162 × 10
size-
designation.
–3
EL-EL20 × 7,7 0,468 64 25,6 54,6 1 400 52,9
8,586 6 × 10
–3
EL-EL22 × 8,0 0,412 80 27,3 66,2 1 810 64,2
6,231 4 × 10
–3
EL-EL25 × 8,6 0,350 34 4,094 2 × 10 30,0 85,6 2 570 83,0
The
combination
EL-PLT
refers to one
taller height
–3
EL-PLT11 × 4,0 0,826 4544 13,7 16,5 226 15,9
49,943 × 10
EL core
paired with
one PLT-core
for each size-
designation.
–3
EL-PLT13 × 4,4 0,666 66 15,4 23,1 357 22,4
28,815 × 10
0,569 74
18,143215 ×
EL-PLT15,5 × 5,8 19,6 32,98 646644 31,9
–3
0,5979 3
–3
EL-PLT18 × 7,3 0,538 3031 12,162 × 10 23,8 44,3 1 050 43,0
–3
EL-PLT20 × 7,7 0,468 6465 8,586 6 × 10 25,6 54,6 1 400 52,9
–3
EL-PLT22 × 8,0 0,412 80 6,231 4 × 10 27,3 66,2 1 810 64,2
–3
EL-PLT25 × 8,6 0,350 34 30,0 85,6 2 570 83,0
4,094 2 × 10
–3
EL-PLT11 × 3,0 0,701 7675 11,7 16,6 194 15,9
42,170 × 10
–3
EL-PLT13 × 3,4 0,577 7170 13,4 23,2 312 22,4
24,857 × 10
0,502 96
15,212273 ×
EL-PLT15,5 × 4,3 16,6 33,10 550549 31,9
–3
0,503 97
–3
EL-PLT18 × 5,3 0,445 54 10,011 × 10 19,8 44,5 882 43,0
–3
EL-PLT20 × 5,7 0,392393 32 21,6 54,9 1 180 52,9
7,167 9 × 10
–3
EL-PLT22 × 6,0 0,350 61 23,4 66,6 1 560 64,2
5,264 5 × 10
–3
EL-PLT25 × 6,6 0,302 2223 26,0 86,0 2 230 83,0
3,515 6 × 10
a
IEC 60205:2016 for the definition of A .
min
4.3 Dimensions and effective parameters of low-profile E-core and mating PLT-core
For the definitions of effective parameters and their calculations, reference shall be made to
IEC 60205.
Figure 2 – Low-profile E-core and mating PLT-core
Table 3 – Dimensions of low-profile E-core and mating PLT-core
Size A B B C D E F
1 2
E14 × 3,5 × 5 Min. 13,70 3,40 4,90 1,90 10,75 2,95
Max. 14,30 3,60 5,10 2,10 11,25 3,05
PLT14 × 1,5 × 5 Min. 13,70 1,40 4,90
Max. 14,30 1,60 5,10
E18 × 4 × 10 Min. 17,65 3,90 9,80 1,90 13,70 3,90
Max. 18,35 4,10 10,20 2,10 14,30 4,10
PLT18 × 2 × 10 Min. 17,65 1,90 9,80
Max. 18,35 2,10 10,20
E22 × 6 × 16 Min. 21,40 5,60 15,50 3,10 16,40 4,90
Max. 22,20 5,80 16,10 3,30 17,20 5,10
PLT22 × 2,5 × 16 Min. 21,40 2,40 15,50
Max. 22,20 2,60 16,10
E32 × 6 × 20 Min. 31,10 6,20 19,90 2,95 24,90 6,20
Max. 32,40 6,50 20,75 3,40 26,10 6,50
PLT32 × 3 × 20 Min. 31,10 3,00 19,90
Max. 32,40 3,35 20,75
E38 × 8 × 25 Min. 37,30 8,10 24,85 4,30 30,20 7,40
Max. 38,90 8,40 25,95 4,60 31,40 7,80
PLT38 × 4 × 25 Min. 37,30 3,65 24,85
Max. 38,90 3,95 25,95
E43 × 10 × 28 Min. 42,30 9,35 27,30 5,25 34,70 7,90
Max. 44,10 9,65 28,50 5,55 36,30 8,30
PLT43 × 4 × 28 Min. 42,30 3,95 27,30
Max. 44,10 4,25 28,50
B B
Size A C D E F
1 2
E58 × 11 × 38 Min. 57,20 10,35 37,30 6,35 50,00 7,90
Max. 59,60 10,75 38,90 6,65 52,20 8,30
PLT58 × 4 × 38 Min. 57,20 3,85 37,30
Max. 59,60 4,25 38,90
E64 × 10 × 50 Min. 62,70 10,05 49,70 4,95 52,50 10,00
Max. 65,30 10,35 51,90 5,25 54,70 10,40
PLT64 × 5 × 50 Min. 62,70 4,95 49,70
Max. 65,30 5,25 51,90
E102 × 20 × 38 Min. 100,0 20,10 36,50 12,90 85,00 13,70
Max. 104,0 20,50 38,50 13,40 88,60 14,30
PLT102 × 7 × 38 Min. 100,0 6,95 36,50
Max. 104,0 7,35 38,50
NOTE All dimensions are expressed in millimetres.

Table 4 – Effective parameter values and A values
min
a
C C l A V
Size A Remarks
1 2 e e e min
–1 –3 2 3 2
mm
mm mm mm mm mm
–3
E-E14 1,380 8 20,7 15,0 311 15,0 Combination
92,055 × 10
–3 E-E
E-E18 0,607 08 24,3 40,0 971 40,0
15,177 × 10
–3
0,410 81 32,5 79,0 2 560 79,0
E-E22 5,200 1 × 10
–3
0,324 85 41,8 129 5 370 127
E-E32 2,525 5 × 10
–3
0,276 13 52,8 191 10 100 185
E-E38 1,443 9 × 10
–3
E-E43 0,274 13 61,6 225 13 800 215
1,219 7 × 10
–3
E-E58 0,269 43 81,3 302 24 500 278
0,893 10 × 10
–3
0,153 67 79,9 520 41 500 518
E-E64
0,295 56 × 10
–3
0,273 88 148 540 80 000 525
E-E102 0,506 86 × 10
–3
1,114 2 16,7 15,0 251 15,0 Combination
E-PLT14 74,277 × 10
–3 E-PLT
E-PLT18 0,507 08 20,3 40,0 811 40,0
12,677 × 10
–3
E-PLT22 0,329 80 26,1 79,0 2 060 79,0
4,174 6 × 10
–3
E-PLT32 0,275 28 35,4 129 4 560 127
2,138 6 × 10
–3
0,229 08 43,9 192 8 420 185
E-PLT38 1,195 0 × 10
–3
0,225 10 50,8 226 11 500 214
E-PLT43 0,996 95 × 10
–3
0,225 00 68,3 304 20 800 278
E-PLT58 0,740 83 × 10
–3
E-PLT64 0,134 18 70,0 519 36 200 518
0,258 30 × 10
–3
E-PLT102 0,225 76 122 539 65 600 525
0,418 68 × 10
NOTE Values ignore the effect of radii. These can have some influence on the outcome of the calculation. They
can be incorporated in the formulae as shown in IEC 60205.
a
See IEC 60205:2016 for the definition of A .
min
4.4 Dimensions and effective parameters of low-profile ER-core and mating PLT-core
For the definitions of effective parameters and their calculations, reference shall be made to
IEC 60205.
Figure 3 – Low-profile ER-core and mating PLT-core
Table 5 – Dimensions of low-profile ER-core and mating PLT-core
Size A B B
C D E F G
1 2
ER9,5 × 2,5 × 5 Min. 9,15 2,375 4,80 1,60 7,50 3,25 7,00
Max. 9,55 2,525 5,00 1,75 7,75 3,55 7,40
PLT9,5 × 1 × 5 Min. 9,15 0,70 4,80
Max. 9,55 0,85 5,00
ER11 × 2,5 × 6 Min. 10,65 2,375 5,80 1,50 8,70 4,00 7,90
Max. 11,00 2,525 6,00 1,65 9,00 4,25 8,30
PLT11 × 1 × 6 Min. 10,65 0,80 5,80
Max. 11,00 0,95 6,00
ER13 × 3 × 9 Min. 12,5 2,775 8,45 1,625 10,9 4,85 8,75
Max. 13,1 2,925 8,95 1,875 11,5 5,15 9,35
PLT13 × 1 × 9 Min. 12,5 1,00 8,45
Max. 13,1 1,20 8,95
ER14,5 × 3 × 7 Min. 14,30 2,90 6,60 1,55 11,6 4,60 11,6
Max. 14,70 3,00 6,80 1,75 12,0 4,80 12,0
PLT14,5 × 1 × 7 Min. 14,30 1,20 6,60
Max. 14,70 1,40 6,80
ER18 × 3 × 10 Min. 17,65 3,05 9,5 1,50 15,3 6,05 13,5
Max 18,35 3,25 9,9 1,70 15,9 6,35 14,1
PLT18 × 1,5 × 10 Min. 17,65 1,45 9,5
Max. 18,35 1,65 9,9
ER20 × 6 × 14 Min. 19,65 6,20 13,7 3,95 17,65 8,65 12,51
Max. 20,35 6,40 14,3 4,25 18,35 8,95 13,21
PLT20 × 2 × 14 Min. 19,65 2,25 13,7
Max. 20,35 2,35 14,3
B B
Size A C D E F G
1 2
ER23 × 3,6 × 13 Min. 22,75 3,50 12,25 1,50 19,8 7,8 17,5
Max. 23,65 3,70 12,75 1,70 20,6 8,2 18,2
ER23 × 5 × 13 Min. 22,75 5,00 12,25 3,00 19,8 7,8 17,5
Max. 23,65 5,20 12,75 3,20 20,6 8,2 18,2
PLT23 × 2 × 13 Min. 22,75 1,90 12,25
Max. 23,65 2,10 12,75
ER25 × 8 × 18 Min. 24,6 7,90 17,7 5,00 21,6 10,8 14,5
Max. 25,4 8,10 18,3 5,30 22,4 11,2 14,9
PLT25 × 3 × 18 Min. 24,6 2,75 17,7
Max. 25,4 2,95 18,3
ER25 × 6 × 15 Min. 24,5 5,40 14,5 3,00 21,3 9,20 18,3
Max. 25,5 5,60 15,1 3,20 22,1 9,60 18,7
PLT25 × 2,4 × 15 Min. 24,5 2,30 14,5
Max. 25,5 2,50 15,1
ER25 × 6 × 18 Min. 24,6 5,55 17,7 3,05 21,6 10,8 14,5
Max. 25,4 5,65 18,3 3,35 22,4 11,2 14,9
PLT25 × 2 × 18 Min. 24,6 2,35 17,7
Max. 25,4 2,45 18,3
ER30 × 8 × 20 Min. 29,6 7,85 19,7 5,10 25,6 10,8 19,05
Max. 30,4 8,15 20,3 5,50 26,4 11,2 19,85
PLT30 × 3 × 20 Min. 29,6 2,60 19,7
Max. 30,4 2,80 20,3
ER32 × 5 × 21 Min. 31,4 5,00 20,6 2,6 29,2 11,0 23,0
Max. 32,6 5,20 21,4 2,8 30,2 11,4 24,2
PLT32 × 2 × 21 Min. 31,4 2,3 20,6
Max. 32,6 2,5 21,4
ER32 × 6 × 25 Min. 31,65 5,84 25,0 2,65 26,8 12,15 26,8
Max. 32,75 6,13 25,8 2,91 27,6 12,55 27,6
PLT32 × 3 × 25 Min. 31,65 3,14 25,0
Max. 32,75 3,34 25,8
ER35 × 10 × 26 Min. 34,6 9,90 25,6 5,00 29,6 14,1 26,4
Max. 35,4 10,1 26,4 5,30 30,4 14,7 27,5
PLT35 × 5 × 26 Min. 34,6 4,75 25,6
Max. 35,4 4,95 26,4
ER40 × 10 × 28 Min. 39,6 9,90 27,6 5,00 34,6 14,6 31,5
Max. 40,4 10,1 28,4 5,30 35,4 15,2 32,5
PLT40 × 5 × 28 Min. 39,6 4,75 27,6
Max. 40,4 4,95 28,4
NOTE All dimensions are expressed in millimetres.

Table 6 – Effective parameter values and A values
min
a
C C l A V
Size A Remarks
1 2 e e e
min
–1 –3 2 3 2
mm
mm mm mm mm mm
–3
1,749 4 8,47 125 Combination
ER9,5 × 2,5 × 5 206,64 × 10 14,8 7,60
–3
ER-ER
1,310 6 11,8 182
ER11 × 2,5 × 6 111,23 × 10 15,4 10,3
–3
0,926 0908 20,0 369
ER13 × 3 × 9 46,376 × 10 18,5 19,1
–3
1,133 5 17,5 349
ER14,5 × 3 × 7 64,620 × 10 19,9 17,3
–3
ER18 × 3 × 10 0,746 41 22,7 30,4 691 30,1
24,539 × 10
–3
ER20 × 6 × 14 0,578 88 34,4 59,4 2 040 55,4
9,741 4 × 10
–3
ER23 × 3,6 × 13 0,545 2526 27,5 50,4 1 380 50,0
10,828 × 10
0,660 31 50,65 1 690
13,059130 ×
ER23 × 5 × 13 33,45 50,0
–3
0,662 77
–3
ER25 × 8 × 18 0,430 02 4,302 6 × 10 43,0 99,9 4 300 95,0
–3
0,497 1617 70,7 2 490
ER25 × 6 × 15 7,030 4 × 10 35,2 69,4
–3
0,374 1112 91,9 3 160
ER25 × 6 × 18 4,070 1 × 10 34,4 86,4
–3
ER30 × 8 × 20 0,440 78 47,5 108 5 110 95,0
4,094 1 × 10
–3
ER32 × 5 × 21 0,400 06 40,2 100 4 030 98,5
3,985 5 × 10
0,300 89
2,099110 3 × 143 6 180170 121
ER32 × 6 × 25 43,12
–3
0,301 81
10 120
0,274 12 200 10 900
1,372 5 369 7 ×
ER35 × 10 × 2726 54,7 163
–3
0,273 80
–3
ER40 × 10 × 28 0,272 7172 59,3 217 12 900 174
1,254 8 × 10
–3
ER9,5 × 2,5 × 5 / 1,394 3 11,5 8,25 95,0 7,60 Combination
168,95 × 10
PLT9,5 × 1 × 5
ER-PLT
–3
ER11 × 2,5 × 6 / 1,082 4 12,4 11,4 141 10,3
94,686 × 10
PLT11 × 1 × 6
0,760 7877
ER13 × 3 × 9 / 38,520519 × 15,0 19,8 297 19,1
–3
PLT13 × 1 × 9 10
–3
ER14,5 × 3 × 7/ 0,947 19 16,6 17,5 290 17,3
54,097 × 10
PLT14,5 × 1 × 7
–3
ER18 × 3 × 10 / 0,643 2726 19,5 30,3 592 30,1
21,212 × 10
PLT18 × 1,5 × 10
–3
ER20 × 6 × 14 / 0,433 67 26,3 60,6 1 590 55,4
7,153 7 × 10
PLT20 × 2 × 14
0,480 86 9,557 1 600 5 × 24,23 50,3 1 220 50,0
ER23 × 3,6 × 13 /
–3
0,482 58
PLT23 × 2 × 13
0,539 38 27,23 50,4 1 370 50,0
ER23 × 5 × 13 / 10,699 751 ×
–3
PLT23 × 2 × 13 0,541 34
–3
ER25 × 8 × 18 / 0,325 66 32,7 100 3 280 95,0
3,243 7 × 10
PLT25 × 3 × 18
0,413 16 5,888 5 782 4 × 29,0 70,28 2 030050 69,4
ER25 × 6 × 15 /
–3
0,409 21
PLT25 × 2,4 × 15
–3
ER25 × 6 × 18 / 0,309 2728 28,0 90,6 2 540 86,4
3,412 1 × 10
PLT25 × 2 × 18
–3
ER30 × 8 × 20 / 0,345 32
37,1 108 4 000 95,0
3,210 0 × 10
PLT30 × 3 × 20
–3
ER32 × 5 × 21 / 0,346 0403 34,8 100 3 490 98,5
3,444 8 × 10
PLT32 × 2 × 21
a
C C l A V
Size A Remarks
1 2 e e e
min
–1 –3 2 3 2
mm
mm mm mm mm mm
0,255 6596 37,78 148 5 570580 121
ER32 × 6 × 25 / 1,731 3 733 5 ×
–3
PLT32 × 3 × 25
0,214 13 1,022 2 020 4 × 44,98 209 210 9 400 163
ER35 × 10 × 26 /
–3
0,213 92
PLT35 × 5 × 26
0,216 83 49,5 228 11300 174
ER40 × 10 × 28 / 0,950 50 51 ×
–3
PLT40 × 5 × 28 10
NOTE Values ignore the effect of radii. These can have some influence on the outcome of the calculation. They
can be incorporated in the formulae as shown in IEC 60205.
a
See IEC 60205:2016 for the definition of A .
min
5 Limits of surface irregularities
5.1 General
Surface irregularities are defined in IEC 60424-1 IEC 63093-1.
5.2 Examples of surface irregularities
Figure 4 shows different examples of surface irregularities for a planar EL-core.

Figure 4 – Examples of surface irregularities for planar EL-core
Figure 5 shows different examples of surface irregularities for a low-profile E-core.

Figure 5 – Examples of surface irregularities for low-profile E-core
Figure 6 shows different examples of surface irregularities for a low-profile ER-core.
Figure 6 – Examples of surface irregularities for low-profile ER-core
5.3 Chips and ragged edges
5.3.1 General
Chips and ragged edges are shown in Figure 7, Figure 8 and Figure 9.
5.3.2 Chips and ragged edges on the mating surfaces
The areas of the chips located on the mating surfaces (C1 and C1' irregularities in Figure 7,
Figure 8 and Figure 9) shall not exceed the following limits:
– the cumulative area of the chips shall be less than 4 % of the relevant mating surface. The
mating surface of each outer leg and centre post is considered separately. The minimum
area is taken as 0,5 mm to be distinguishable to the naked eye;
– the total length of the ragged edges shall be less than 25 % of the perimeter of the relevant
mating surface.
Figure 7 – Chip location for planar EL-core

Figure 8 – Chip location for low-profile E-core
Figure 9 – Chip location for low-profile ER-core
5.3.3 Chips and ragged edges on other surfaces
For chips and ragged edges located on the surfaces:
– the allowable chipping areas are doubled as compared to the limits for the whole mating
surfaces;
– the total length of the ragged edges shall be less than 25 % of the perimeter of the smaller
adjoining surface;
– chips and ragged edges are not acceptable on the inner edges of the wire slot area
(see C2 irregularity in Figure 8 and Figure 9).
Area and length reference for visual inspection are given in Table 7. Reference values of
allowable areas of chips are given in Annex B.
Table 7 – Area and length reference for visual inspection

5.4 Cracks
Different cracks are shown in Figure 10, Figure 11 and Figure 12. In principle three different
types of cracks can be distinguished.
a) Cracks which are parallel to the magnetic flux path (S1, S2, S5, S5', S5''). These cracks are
magnetically not critical. The maximum length of a single crack is 33 % (1/3) of the
dimension of the relevant surface which is parallel to the crack. In the case of multiple cracks
the maximum cumulative length doubles.
b) Cracks which are perpendicular to the magnetic flux path (S3, S3', S3'', S4, S4'). These
cracks are magnetically critical. They can reduce the relative cross-section of the magnetic
flux or add an additional air gap into the magnetic circuit. The maximum total length of
cracks is 20 % (1/5) of the dimension of the relevant surface which is parallel to the crack.
c) Cracks which go from one edge to another edge (S6). These cracks can cause chipping
during the operation in the circuit. The loose particles can cause malfunctions in the circuit.
Therefore, this type of crack is not acceptable in any case.
The reference dimensions are given in Figure 13, Figure 14 and Figure 15.
The limits for cracks are given in Table 8, Table 9 and Table 10.
5.5 Flash
There shall be no flash extending from the core into the wire slot.
5.6 Pull-outs
The pull-outs are applicable only for the inner surface where the PCB is seated (as shown in
Figure 10, Figure 11 and Figure 12).
For planar EL-cores, low-profile E-cores and low-profile ER-cores, the cumulative area of pull-
outs of the core shall be less than 20 % of the total respective surface area.

Figure 10 – Cracks and pull-out location for planar EL-core
Figure 11 – Cracks and pull-out location for low-profile E-core

Figure 12 – Cracks and pull-out location for low-profile ER-core

Figure 13 – Reference dimensions for EL-core
Table 8 – Limits of cracks for planar EL-core
a b
Limits for single crack Limits for multiple cracks
Type Reference dimension
S1 F 33 % (1/3) of reference dim. 66 % (2/3) of reference dim.
S2 (A-E)/2 33 % (1/3) of reference dim. 66 % (2/3) of reference dim.
S3 F 20 % (1/5) of reference dim. 20 % (1/5) of reference dim.
S3' F 20 % (1/5) of reference dim. 20 % (1/5) of reference dim.
S3'' C 20 % (1/5) of reference dim. 20 % (1/5) of reference dim.
S4 B – D 20 % (1/5) of reference dim. 20 % (1/5) of reference dim.
S4' B – D 20 % (1/5) of reference dim. 20 % (1/5) of reference dim.
S5 B 33 % (1/3) of reference dim. 66 % (2/3) of reference dim.
S5' A 33 % (1/3) of reference dim. 66 % (2/3) of reference dim.
S5" A 33 % (1/3) of reference dim. 66 % (2/3) of reference dim.
S6 Multiple edges No cracks allowed
a
See Figure 10.
b
See Figure 13.
Figure 14 – Reference dimensions for E-core
Table 9 – Limits of cracks for low-profile E-core
a b
Limits for single crack Limits for multiple cracks
Type Reference dimension
S1 F 33 % (1/3) of reference dim. 66 % (2/3) of reference dim.
S2 (A-E)/2 33 % (1/3) of reference dim. 66 % (2/3) of reference dim.
S3 C 20 % (1/5) of reference dim. 20 % (1/5) of reference dim.
S3' F 20 % (1/5) of reference dim. 20 % (1/5) of reference dim.
S3'' C 20 % (1/5) of reference dim. 20 % (1/5) of reference dim.
S4 B – D 20 % (1/5) of reference dim. 20 % (1/5) of reference dim.
S4' B – D 20 % (1/5) of reference dim. 20 % (1/5) of reference dim.
S5 B 33 % (1/3) of reference dim. 66 % (2/3) of reference dim.
S5' A 33 % (1/3) of reference dim. 66 % (2/3) of reference dim.
a b
Limits for single crack Limits for multiple cracks
Type Reference dimension
S5" A 33 % (1/3) of reference dim. 66 % (2/3) of reference dim.
S6 Multiple edges No cracks allowed
a
See Figure 11.
b
See Figure 14.
Figure 15 – Reference dimensions for ER-core
Table 10 – Limits of cracks for low-profile ER-core
a b
Limits for single crack Limits for multiple cracks
Type Reference dimension
S1 F 33 % (1/3) of reference dim. 66 % (2/3) of reference dim.
S2 (A-G)/2 33 % (1/3) of reference dim. 66 % (2/3) of reference dim.
S3 F 20 % (1/5) of reference dim. 20 % (1/5) of reference dim.
S3'' C 20 % (1/5) of reference dim. 20 % (1/5) of reference dim.
S4 B – D 20 % (1/5) of reference dim. 20 % (1/5) of reference dim.
S4' B – D 20 % (1/5) of reference dim. 20 % (1/5) of reference dim.
S5 B 33 % (1/3) of reference dim. 66 % (2/3) of reference dim.
S5' A 33 % (1/3) of reference dim. 66 % (2/3) of reference dim.
S5" A 33 % (1/3) of reference dim. 66 % (2/3) of reference dim.
S6 Multiple edges No cracks allowed
a
See Figure 12.
b
See Figure 15.
5.7 Crystallites
An example of the location of a crystallite on the planar core is shown in Figure 16, Figure 17
and Figure 18:
– the single area of the crystallite located on any surface shall be less than 2 % of the
respective surface area;
– the cumulative area of the crystallites located on any surface shall be less than 4 % of the
respective surface area.
Figure 16 – Example of the location of a crystallite on planar EL-core

Figure 17 – Example of the location of a crystallite on low-profile E-core

Figure 18 – Example of the location of a crystallite on low-profile ER-core
5.8 Pores
An example of the location of a pore on the planar core is shown in Figure 19, Figure 20 and
Figure 21.
The number of pores and the area of the pores shall not exceed the following limits.
If the A dimension ( see Figure 13, Figure 14 and Figure 15) is shorter than 20 mm:
– the number of pores located on the same surface shall not exceed one; the numbers of
pores located on all surfaces shall not exceed three;
– a pore with an area larger than 0,5 mm on any surface is not acceptable.
...