IEC 63093-5:2025

Ferrite cores - Guidelines on dimensions and the limits of surface irregularities - Part 5: EP-cores and associated parts for use in inductors and transformers

IEC 63093-5:2025 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 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.
This edition includes the following significant technical changes with respect to the previous edition:
a) revision of Table 2 according to IEC 60205:2016.

Noyaux ferrites - Lignes directrices relatives aux dimensions et aux limites des irrégularités de surface - Partie 5: Noyaux EP et pièces associées utilisés dans les inductances et transformateurs

General Information

• Status: Published
• Publication Date: 14-Dec-2025
• ICS: 29.100.10 - Magnetic components
• Technical Committee: TC 51 - Magnetic components, ferrite and magnetic powder materials
• Drafting Committee: WG 1 - TC 51/WG 1
• Current Stage: PPUB - Publication issued
• Start Date: 15-Dec-2025
• Completion Date: 02-Jan-2026

Relations

• Revises: IEC 63093-5:2018 - Ferrite cores - Guidelines on dimensions and the limits of surface irregularities - Part 5: EP-cores and associated parts for use in inductors and transformers
• Effective Date: 22-Dec-2023

Overview

IEC 63093-5:2025 - "Ferrite cores - Guidelines on dimensions and the limits of surface irregularities - Part 5: EP‑cores and associated parts for use in inductors and transformers" defines mechanical and visual requirements for a preferred range of EP‑cores (sizes EP5 to EP30) made of ferrite. The standard specifies the principal dimensions that ensure mechanical interchangeability, essential coil‑former dimensions, terminal‑pin locations on a 2.50 mm printed wiring grid, and the effective magnetic parameters to be used in calculations. It also gives illustrated guidance and numerical limits for allowable surface irregularities (chips, cracks, flash, pull‑outs, crystallites, pores) useful in supplier–user negotiations.

Key topics and technical requirements

• Mechanical interchangeability: Principal dimensions and tolerances for EP‑core sizes (EP5…EP30) to ensure assemblies and wound coil formers fit across suppliers.
• Coil former dimensions: Essential limits for formers that mate with EP‑cores (see main dimensions and tables for e, f, d, s, etc.).
• Pin locations and base outlines: Terminal pin coordinates referenced to a 2.50 mm PCB grid for both SMD and PTH versions, with base outlines relative to mounting direction.
• Effective parameters: Effective magnetic parameters and A‑values are tabulated (Table 2) and calculated per IEC 60205; the standard instructs use of K(nom.) for those calculations.
• Surface irregularities: Definitions, examples (figures), and numerical acceptance criteria:
  • Minimum visually distinguishable area: 0.5 mm²
  • For chips on mating surfaces, cumulative chip area must be < 4% of the relevant mating surface (ring and centre pole considered separately)
  • Detailed limits for cracks, flash, pull‑outs, crystallites and pores with inspection reference areas and visual limits are provided.

Applications and users

This part of IEC 63093 is intended for:

• Ferrite core manufacturers and suppliers - to dimension products and set acceptable surface quality.
• Designers of inductors, transformers and magnetic assemblies - to select cores and coil formers that guarantee mechanical interchangeability.
• PCB and component layout engineers - for correct pin‑grid placement (2.50 mm grid) and footprint design.
• Procurement and quality engineers - for supplier agreements, inspection criteria and acceptance testing of ferrite EP‑cores.

Practical benefits include reduced redesign risk, consistent assembly fit, reliable electromagnetic parameter use in calculations, and clearer supplier–user quality agreements.

Related standards

• IEC 60205 - Calculation of the effective parameters of magnetic piece parts (referenced for parameter computations).
• IEC 60401‑1 - Terms and nomenclature for ferrite cores (physical irregularities and dimensions).
• IEC 63093‑1 - General specification for ferrite cores (definitions and general limits of surface irregularities).

Keywords: IEC 63093-5:2025, ferrite cores, EP‑cores, surface irregularities, coil formers, inductors, transformers, mechanical interchangeability, effective parameters, 2.50 mm PCB grid.

Standards Content (Sample)

IEC 63093-5 ®
Edition 2.0 2025-12
INTERNATIONAL
STANDARD
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 978-2-8327-0907-8

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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 (informative) EP-core design. 15
A.1 General . 15
A.2 Pin location and base outlines . 15

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. 6
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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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 51/15
...