IEC 63093-5:2025

IEC 63093-5 ®
Edition 2.0 2025-12
INTERNATIONAL
STANDARD
REDLINE VERSION
Ferrite cores - Guidelines on dimensions and the limits of surface irregularities -
Part 5: EP-cores and associated parts for use in inductors and transformers
ICS 29.100.10 ISBN 978-2-8327-0952-8
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CONTENTS
FOREWORD. 2
1 Scope . 4
2 Normative references . 4
3 Terms and definitions . 4
4 Primary dimensions . 4
4.1 General . 4
4.2 Dimensions of EP-cores . 5
4.2.1 Principal dimensions . 5
4.2.2 Effective parameter and A values . 5
min
4.3 Dimensional limits for coil formers . 6
4.4 Pin locations and base outlines . 7
5 Limits of surface irregularities . 8
5.1 General . 8
5.2 Examples of surface irregularities . 9
5.3 Chips and ragged edges . 9
5.3.1 General . 9
5.3.2 Chips and ragged edges on the mating surfaces . 9
5.3.3 Chips and ragged edges on the other surfaces . 10
5.4 Cracks . 12
5.5 Flash . 12
5.6 Pull-outs . 12
5.7 Crystallites . 13
5.8 Pores . 14
Annex A (normativeinformative) EP-core design . 15
A.1 General . 15
A.2 Pin location and base outlines . 15
Bibliography .

Figure 1 – Principal dimensions of EP-cores . 5
Figure 2 – Main dimensions of coil formers for EP-cores . 6
Figure 3 – Pin locations (SMD type) viewed from the upper side of the board . 7
Figure 4 – Pin locations (PTH type) viewed from the underside of the board . 8
Figure 5 – Examples of surface irregularities . 9
Figure 6 – Chip and ragged edge location for EP-cores . 10
Figure 7 – Crack flash and pull-out locations for EP-cores . 12
Figure 8 – Crystallite location for EP-cores . 13
Figure 9 – Pore location for EP-cores . 14

Table 1 – Principal dimensions of EP-cores . 5
Table 2 – Effective parameter and A values . 6
min
Table 3 – Dimensional limits for coil formers for EP-cores . 7
Table 4 – Area and length reference for visual inspection . 11
Table 5 – Limits for cracks . 13
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
Ferrite cores - Guidelines on dimensions
and the limits of surface irregularities -
Part 5: EP-cores and associated parts
for use in inductors and transformers

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 63093-5:2018. 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 63093-5 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 2018. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) revision of Table 2 according to IEC 60205:2016.
The text of this International Standard is based on the following documents:
Draft Report on voting
51/1580/FDIS 51/1589/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 63093 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.
1 Scope
This part of IEC 63093 specifies the dimensions that are of importance for mechanical
interchangeability for a preferred range of EP-cores made of ferrite, the essential dimensions
of coil formers to be used with them and the locations of their terminal pins on a 2,50 mm printed
wiring grid in relation to the base outlines of the cores and the effective parameter values to be
used in calculations involving them. It also gives guidelines on allowable limits of surface
irregularities applicable to EP-cores.
The specifications contained in this document are useful in negotiations between ferrite core
manufacturers suppliers and users about surface irregularities.
The general considerations upon which the design of this range of cores is based are as 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, 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 General
Compliance with the following requirements ensures mechanical interchangeability of complete
assemblies and wound coil formers.
4.2 Dimensions of EP-cores
4.2.1 Principal dimensions
The principal dimensions of EP-cores shall be those given in Figure 1 and Table 1.

Figure 1 – Principal dimensions of EP-cores
Table 1 – Principal dimensions of EP-cores
A C K E F 2B 2D
Size mm mm mm mm mm mm mm
Min. Max. Min. Max. Max. Min. Max. Min. Max. Min. Max. Min. Max.
EP5 5,85 6,15 3,70 3,90 1,00 4,25 4,55 1,60 1,80 5,50 5,70 3,80 4,20
EP7 9,00 9,40 6,20 6,50 1,80 7,20 7,60 3,20 3,40 7,30 7,50 5,00 5,40
EP10 11,2 11,8 7,45 7,85 1,95 9,20 9,60 3,15 3,45 10,0 10,4 7,20 7,60
EP13 12,2 12,8 8,60 9,00 2,50 9,70 10,3 4,20 4,50 12,7 13,0 9,00 9,40
EP17 17,6 18,4 10,75 11,25 3,45 11,6 12,4 5,50 5,85 16,6 17,0 11,0 11,6
EP20 23,5 24,5 14,6 15,3 4,70 16,1 16,9 8,50 9,00 21,2 21,6 14,0 14,6
EP30 30,5 31,5 22,6 23,6 7,85 23,6 24,4 14,5 15,0 29,7 30,0 23,0 23,8

4.2.2 Effective parameter and A values
min
The effective parameter values of a pair of cores having the dimensions given in 4.2.1 are as
shown in Table 2. For the definitions of these parameters and their calculations, reference shall
be made to IEC 60205.
Table 2 – Effective parameter and A values
min
a
C C l A V
A
1 2 e e e
min
Size
–1 –3 2 3 2
mm
mm mm mm mm mm
-3
EP5
1 080,4 × 10
3,255 83,205 2 9,819,62 3,013,00 29,628,9 2,27
-3
1 067,8 × 10
-3
EP7
138,76 × 10
1,479 91,451 6 15,815,5 10,7 168166 8,55
-3
135,61 × 10
-3
EP10
152,21 × 10
1,726 51,697 6 19,619,2 11,3 222217 8,55
-3
150,06 × 10
-3
EP13
64,783 × 10
1,264 21,236 6 24,724,2 19,5 481472 14,9
-3
63,296 × 10
-3
EP17
25,187 × 10
0,854 960,839 99 29,028,4 33,9 985964 25,3
-3
24,801 × 10
-3
EP20
6,603 8 × 10
0,518 140,508 19 40,740,0 78,578,7 3 1903 150 60,1
-3
6,456 3 × 10
-3
EP30
1,990 1 × 10
0,353 760,349 37 62,962,6 178179 11 200 128
-3
1,950 6 × 10
When effective parameters are calculated, K(nom.) shall be used. K(nom.) = K(max.) - (K(max.) - F(nom.)/2)/2.
NOTE The above values have been calculated using the method given in IEC 60205.
a
A is selected as the smallest value among A , A , A , A and A using the mean value of each dimension.
min 1 2 3 4 5
4.3 Dimensional limits for coil formers
The main dimensions of coil formers suitable for use with a pair of EP-cores shall be as given
in Figure 2 and Table 3.
Figure 2 – Main dimensions of coil formers for EP-cores
Table 3 – Dimensional limits for coil formers for EP-cores
e f f d s
1 2
Size
mm mm mm mm mm
Min. Max. Min. Max. Min. Max. Min. Max. Min. Max.
EP5 4,00 4,20 2,65 2,85 1,85 2,05 3,50 3,70 0,30 0,50
EP7 6,70 7,00 4,30 4,70 3,60 3,80 4,45 4,75 0,60 0,80
EP10 8,60 9,00 4,65 4,95 3,60 3,80 6,70 7,00 0,50 0,70
EP13 9,30 9,60 5,55 5,85 4,60 4,80 8,60 8,90 0,45 0,65
EP17 11,1 11,4 7,05 7,35 6,00 6,30 10,6 10,9 0,55 0,75
EP20 15,6 15,9 10,0 10,3 9,10 9,40 13,5 13,9 0,55 0,75
EP30 23,1 23,5 16,7 17,0 15,1 15,4 22,5 22,9 0,80 1,00

4.4 Pin locations and base outlines
Pin locations and base outlines shall be as shown in Figure 3, in which the base is viewed in
the mounting direction, i.e. from the upper side of the printed wiring board, and in Figure 4, in
which the base is viewed from the pin side, i.e. from the underside of the printed wiring board.

NOTE All dimensions are expressed in millimetres.
Figure 3 – Pin locations (SMD type) viewed from the upper side of the board
NOTE 2,50 mm grids. Each grid is 2,5 mm.
Figure 4 – Pin locations (PTH type) viewed from the underside of the board
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 5 shows different examples of surface irregularities of an EP-core.

Figure 5 – Examples of surface irregularities
5.3 Chips and ragged edges
5.3.1 General
The minimum area is taken as 0,5 mm , to be distinguishable to the naked eye.
5.3.2 Chips and ragged edges on the mating surfaces
The areas of the chips located on the mating surfaces (Chip 1 and Chip 1' irregularities in
Figure 6) 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 ring and centre pole are considered separately;
– the total length of the ragged edges shall be less than 25 % of the perimeter of the relevant
surface.
5.3.3 Chips and ragged edges on the other surfaces
The allowable areas of chips on the other surfaces are doubled as compared to the limits for
the mating surface of the ring (outer leg), see Figure 6. The rule for ragged edges is the same
as that for the mating surface.

Figure 6 – Chip and ragged edge location for EP-cores
Area and length reference for visual inspection is given in Table 4.
Table 4 – Area and length reference for visual inspection

5.4 Cracks
The limits for cracks at various locations shown in Figure 7 are given in Table 5.
5.5 Flash
There shall be no flash extending from the core into the wire slot (see Figure 7).
5.6 Pull-outs
For EP-cores, the cumulative area of pull-outs of the core shall be less than 25 % of the total
respective surface area (see Figure 7).

Figure 7 – Crack flash and pull-out locations for EP-cores
Table 5 – Limits for cracks
Type Location Limits for single crack Limits for multiple
cracks
S1 Bottom corner of ring and 10 % of the length of 20 % of the length of
back wall bottom corner of ring bottom corner of ring
(outer leg) and back wall (outer leg) and back wall
S2 Mating surface of ring, 50 % of minimum Minimum thickness of ring
angle shape thickness of ring (outer (outer leg)
leg)
S3 Vertical against ring 50 % of minimum Minimum thickness of ring
thickness of ring (outer (outer leg)
leg)
S4 Parallel with ring Minimum thickness of ring 2 × minimum thickness of
(outer leg) ring (outer leg)
S5 Bottom corner of centre 10 % of the length of 20 % of the length of
pole and back wall bottom corner of centre bottom corner of centre
pole and back wall pole and back wall
S6, S7 and S8 Mating surface of centre 20 % of diameter of 40 % of diameter of
pole centre pole centre pole
S8' Side wall of centre pole, 20 % of diameter of 40 % of diameter of
parallel with mating centre pole centre pole
surface
S9 Back wall 50 % of dimension T Dimension T
S10 and S11 Back wall 50 % of dimension T Dimension T
S12 Back surface Dimension T 2 × dimension T

5.7 Crystallites
Figure 8 shows an example of crystallite location on EP-cores:
– a single area of the crystallites 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 8 – Crystallite location for EP-cores
5.8 Pores
Figure 9 shows an example of pore location on EP-cores:
– the number of pores located on the same surface shall not exceed two; the total number of
pores located on all surfaces shall not exceed five;
– a hole with an area larger than 1 mm on any surface is not acceptable.

Figure 9 – Pore location
...