IEC 60424-8:2015

IEC 60424-8 ®
Edition 1.0 2015-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Ferrite cores – Guidelines on the limits of surface irregularities –
Part 8: PQ-cores
Noyaux ferrites – Lignes directrices relatives aux limites des irrégularités de
surface –
Partie 8: Noyaux PQ
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IEC 60424-8 ®
Edition 1.0 2015-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Ferrite cores – Guidelines on the limits of surface irregularities –

Part 8: PQ-cores
Noyaux ferrites – Lignes directrices relatives aux limites des irrégularités de

surface –
Partie 8: Noyaux PQ
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.100.10 ISBN 978-2-8322-2803-6

– 2 – IEC 60424-8:2015 © IEC 2015

CONTENTS
FOREWORD . 3

1 Scope . 5

2 Normative references . 5

3 Terms and definitions . 5

4 Limits of surface irregularities . 6

4.1 Chips and ragged edges . 6

4.1.1 Chips and ragged edges located on the mating surface . 6
4.1.2 Chips located on other surfaces . 6
4.2 Cracks . 9
4.3 Pull-out . 10
4.4 Crystallites . 10
4.5 Flash . 11
4.6 Pores . 11
Bibliography . 13

Figure 1 – Examples of surface irregularities . 5
Figure 2 – Chips and ragged edges location . 6
Figure 3 – Cracks location . 9
Figure 4 – Reference dimensions for PQ-cores . 9
Figure 5 – Pull-out location . 10
Figure 6 – Crystallites location . 11
Figure 7 – Flash location. 11
Figure 8 – Pores location . 12

Table 1 – Limits for allowable chipping areas . 7
Table 2 – Area and length reference of irregularities for visual inspection . 8
Table 3 – Limits for cracks . 10

INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________
FERRITE CORES –
GUIDELINES ON THE LIMITS OF SURFACE IRREGULARITIES –

Part 8: PQ-cores
FOREWORD
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International Standard IEC 60424-8 has been prepared by technical committee 51: Magnetic
components and ferrite materials.
The text of this standard is based on the following documents:
CDV Report on voting
51/1078/CDV 51/1084/RVC
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

– 4 – IEC 60424-8:2015 © IEC 2015

A list of all parts in the IEC 60424 series, published under the general title Ferrite cores –

Guidelines on the limits of surface irregularities, can be found on the IEC website.

Future standards in this series will carry the new general title as cited above. Titles of existing

standards in this series will be updated at the time of the next edition.

The committee has decided that the contents of this publication will remain unchanged until

the stability date indicated on the IEC website 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.
FERRITE CORES –
GUIDELINES ON THE LIMITS OF SURFACE IRREGULARITIES –

Part 8: PQ-cores
1 Scope
This part of IEC 60424 gives guidance on allowable limits of surface irregularities applicable
to PQ-cores in accordance with the relevant generic specification.
This standard is considered as a sectional specification useful in the negotiation between
ferrite core manufacturers and users about surface irregularities.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60401-1, Terms and nomenclature for cores made of magnetically soft ferrites – Part 1:
Terms used for physical irregularities
IEC 60424-1, Ferrite cores – Guide on 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 60424-1 and
IEC 60401-1, as well as the following apply.
3.1
pores
holes left on the surface of cores after sintering and surface finishing
SEE: Figure 1.
IEC
Figure 1 – Examples of surface irregularities

– 6 – IEC 60424-8:2015 © IEC 2015

4 Limits of surface irregularities

4.1 Chips and ragged edges
4.1.1 Chips and ragged edges located on the mating surface

The areas of the chips located on the mating surface (see C1 and C1’ irregularities in Figure 2)

shall not exceed the following limits:

– the cumulative area of the chips located on the mating surface shall be less than 4 % of

the total mating surface;
– the cumulative area of the chips located on the centre post mating surface shall be less
than 2 % of the total mating surface;
– the cumulative area of the chips located on the mating surface of one outer leg shall be
less than 1 % of the total mating surface;
The total length of the ragged edges shall be less than 25 % of the perimeter of the relevant
mating surface.
4.1.2 Chips located on other surfaces
The areas of the chips located on the other surfaces (see C2, C2’, C3 and C3’ irregularities in
Figure 2) shall not exceed the following limits:
– the allowable chipping areas are doubled as compared to the limits for the whole mating
surfaces (see Table 1);
– the rule for the ragged edges is the same as for the mating surfaces;
– chips and ragged edges are not acceptable on the inner edges of the wire slot area.

IEC
Figure 2 – Chips and ragged edges location
The limits of allowable chipping areas shall be in accordance with Table 1.

Table 1 – Limits for allowable chipping areas

Unit: mm
Chipping on Chipping on
Overall chipping Overall chipping

Core size mating surface of mating surface of
on mating surface on other surfaces
one outer leg centre post
PQ20/16
< 1,0 < 2,0 < 4,5 < 9,0
PQ20/20 < 1,0 < 2,0 < 4,5 < 9,0

PQ26/20
< 2,0 < 4,5 < 9,5 < 19,0
PQ26/25
< 2,0 < 4,5 < 9,5 < 19,0
PQ32/20 < 3,0 < 6,0 < 12,0 < 24,0
PQ32/30 < 3,0 < 6,0 < 12,0 < 24,0
PQ35/35
< 3,0 < 6,5 < 13,0 < 26,0
PQ40/40 < 3,5 < 7,0 < 14,0 < 28,0
PQ50/50 < 6,0 < 12,5 < 25,0 < 50,0
NOTE For the relevant core sizes refer to IEC 62317-13.

The area and length reference of irregularities for visual inspection are given in Table 2.

– 8 – IEC 60424-8:2015 © IEC 2015

Table 2 – Area and length reference of irregularities for visual inspection

IEC
4.2 Cracks
Figure 3 shows examples of cracks location on PQ-cores:

– a single crack which intersects the perimeter of the relevant surface at two points is not
acceptable (see S1 in Figure 3);

– the number of the cracks located on the same surface shall not exceed 3.

The limits of cracks at various locations shown in Figure 3 are given in Table 3.

IEC
Key
S1 to S8: types of cracks (for limits for cracks, see Table 3)
Figure 3 – Cracks location
The reference dimensions for PQ-cores given in Figure 4 correspond to the cores defined in
IEC 60401-2.
IEC
Key
A Overall length of the core back
B Outside leg length of core
C Core width
D Inside leg length or available bobbin depth
F Centre post diameter
Figure 4 – Reference dimensions for PQ-cores
...