IEC 60715:2017

Dimensions of low-voltage switchgear and controlgear - Standardized mounting on rails for mechanical support of switchgear, controlgear and accessories

IEC 60715:2017 specifies dimensional and functional requirements for the compatible mounting of switchgear, controlgear and accessories on some types of rails.
This second edition cancels and replaces the first edition published in 1981 and Amendment 1:1995. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous edition:
a) the electrical function of the rail for protective earthing is covered by the relevant product standard.
b) the document has been editorially updated to bring it into compliance with the ISO/IEC Directives, Part 2:2016, and drawings have been updated to bring them in compliance with ISO tolerancing and drawing standards.
It has the status of a horizontal standard in accordance with IEC Guide 108.

Dimensions de l'appareillage à basse tension - Montage normalisé sur profilés-supports pour le support mécanique des appareillages et de leurs accessoires

IEC 60715:2017 spécifie les exigences dimensionnelles et fonctionnelles destinées à assurer la compatibilité du montage des appareillages et de leurs accessoires sur certains types de profilés-supports.
Cette deuxième édition annule et remplace la première édition parue en 1981 et l'Amendement 1:1995. Cette édition constitue une révision technique.
Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
a) la fonction électrique de conducteur de protection du profilé-support est couverte par la norme de produit correspondante.
b) Le document a fait l’objet d’une mise à jour éditoriale visant à le rendre conforme aux Directives ISO/IEC, Partie 2:2016 et les dessins ont fait l’objet d’une mise à jour afin d’être conformes aux normes ISO de tolérancement et de dessin.
Elle a le statut de norme horizontale conformément au Guide IEC 108.

General Information

• Status: Published
• Publication Date: 27-Jul-2017
• ICS: 29.035.01 - Insulating materials in general
• ICS: 29.130.20 - Low voltage switchgear and controlgear
• Technical Committee: SC 121A - Low-voltage switchgear and controlgear
• Current Stage: PPUB - Publication issued
• Start Date: 28-Jul-2017
• Completion Date: 25-Aug-2017

Standards Content (Sample)

IEC 60715 ®
Edition 2.0 2017-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
HORIZONTAL STANDARD
NORME HORIZONTALE
Dimensions of low-voltage switchgear and controlgear – Standardized mounting
on rails for mechanical support of switchgear, controlgear and accessories

Dimensions de l'appareillage à basse tension – Montage normalisé sur profilés-
supports pour le support mécanique des appareillages et de leurs accessoires

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IEC 60715 ®
Edition 2.0 2017-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
HORIZONTAL STANDARD
NORME HORIZONTALE
Dimensions of low-voltage switchgear and controlgear – Standardized mounting

on rails for mechanical support of switchgear, controlgear and accessories

Dimensions de l'appareillage à basse tension – Montage normalisé sur profilés-

supports pour le support mécanique des appareillages et de leurs accessoires

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.130.20 ISBN 978-2-8322-4646-7

– 2 – IEC 60715:2017 © IEC 2017
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 8
4 Functional requirements . 8
5 Standard dimensions . 8
5.1 General . 8
5.2 Top hat section . 9
5.3 "C" section . 10
5.4 "G" section . 13
Annex A (normative)  Specific steel mounting rails . 14
A.1 General . 14
A.2 Top hat section rail TH 15-5,5 . 14
A.2.1 Dimensions . 14
A.2.2 Tolerances . 15
A.3 Top hat section rail TH 35-7,5 and TH 35-15 . 15
A.3.1 Dimensions . 15
A.3.2 Tolerances . 16
A.4 Top hat section rail TH 75-25 . 16
A.4.1 Dimensions . 16
A.4.2 Tolerances . 17
A.5 "C" section rails: C 20, C 30, C 40 and C 50 . 17
A.5.1 Dimensions . 17
A.5.2 Tolerance . 18
A.6 "G" section rail: G 32 . 18
A.6.1 Dimensions . 18
A.6.2 Tolerances . 19
Annex B (informative) Application guide . 20
B.1 General . 20
B.2 Guidance for use of top hat rails . 20
B.2.1 For steel rails in Annex A . 20
B.2.2 For rails other than steel rails . 23
B.3 Guidance for use of "C" section rails . 23
B.3.1 General . 23
B.3.2 For steel rails to Annex A . 23
B.3.3 For rails other than steel rails . 27
Bibliography . 28

Figure 1 – Mounting rail TH 15 . 9
Figure 2 – Mounting rail TH 35 . 9
Figure 3 – Mounting rail TH 75 . 10
Figure 4 – Mounting rail C 20 . 10
Figure 5 – Mounting rail C 30 . 11
Figure 6 – Mounting rail C 40 . 11

Figure 7 – Mounting rail C 50 . 12
Figure 8 – Mounting rail G 32 . 13
Figure A.1 – Top hat rails 15 mm wide for snap-on mounting of equipment . 15
Figure A.2 – Tolerances (TH 15-5,5) . 15
Figure A.3 – Top hat rails 35 mm wide for snap-on mounting of equipment . 16
Figure A.4 – Tolerances (TH 35-7,5 and TH 35-15) . 16
Figure A.5 – Top hat rail 75 mm wide for snap-on mounting of equipment . 17
Figure A.6 – Tolerances (TH 75-25) . 17
Figure A.7 – "C" section rails . 18
Figure A.8 – Tolerances (C 20, C 30, C 40 and C 50) . 18
Figure A.9 – Dimensions of "G" section rails . 19
Figure A.10 – Tolerances (G 32) . 19
Figure B.1 – Assessment of rail deflection . 21
Figure B.2 – Permissible load capacity . 22
M = f(L,h)
E
Figure B.3 – Permissible load capacity M = f(L,h) . 23
E
Figure B.4 – Assessment of rail deflection . 24
Figure B.5 – Permissible load capacity M = f(L) . 25
E
Figure B.6 – Assembly of two identical "C" section rails Assessment of the deflection . 26
Figure B.7 – Assembly of two identical "C" section rails Permissible stress M = f(L)
E
for H = 100 mm . 27

Table A.1 – Dimensions of “C” section rails . 18
Table B.1 – Maximum torque M . 24
max
– 4 – IEC 60715:2017 © IEC 2017
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
DIMENSIONS OF LOW-VOLTAGE SWITCHGEAR AND CONTROLGEAR –
STANDARDIZED MOUNTING ON RAILS FOR MECHANICAL SUPPORT
OF SWITCHGEAR, CONTROLGEAR AND ACCESSORIES

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, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for 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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Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
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4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
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between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
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Publications.
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 60715 has been prepared by subcommittee 121A: Low-voltage
switchgear and controlgear, of IEC technical committee 121: Switchgear and controlgear and
their assemblies for low voltage.
This second edition cancels and replaces the first edition published in 1981 and
Amendment 1:1995. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) the electrical function of the rail for protective earthing is covered by the relevant product
standard.
b) The document has been editorially updated to bring it into compliance with the ISO/IEC
Directives, Part 2:2016, and drawings have been updated to bring them in compliance with
ISO tolerancing and drawing standards.

It has the status of a horizontal standard in accordance with IEC Guide 108.
The text of this International Standard is based on the following documents:
FDIS Report on voting
121A/153/FDIS 121A/163/RVD
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
– 6 – IEC 60715:2017 © IEC 2017
INTRODUCTION
This document is provided as a horizontal standard. It is necessary to define standardized
mounting on rails for mechanical support of low-voltage switchgear and controlgear, electrical
accessories, and similar devices.
The user wants them to be easy to fix, remove and rearrange.
Two methods are used for fixing a device on a rail:
– either directly by clipping on the rail (this method is particularly suitable for "top hat" rails
or "G" rails);
– or by means of a variety of accessories such as sliding nuts and hooked or T-headed bolts
(this method is particularly suitable for "C" rails).
In the case of "G" rails, the first of these methods has been mainly used for mounting terminal
blocks which snap in and out of position and are clamped in rows by adjustable end stops.
The rail can take the form of a standard section as an integral part of the enclosure.
Rails are also available of composite sections that combine, for example, "top hat" and "C"
section sizes thus accepting devices with various arrangements for mounting.
One or more rails can be used as necessary for fixing devices.
Since rail mounting can affect the performance of equipment, it can be advisable for
equipment manufacturers to give guidance in their literature on the suitability for this form of
mounting.
DIMENSIONS OF LOW-VOLTAGE SWITCHGEAR AND CONTROLGEAR –
STANDARDIZED MOUNTING ON RAILS FOR MECHANICAL SUPPORT
OF SWITCHGEAR, CONTROLGEAR AND ACCESSORIES

1 Scope
This document specifies dimensional and functional requirements for the compatible mounting
of switchgear, controlgear and accessories on some types of rails.
The object of this document is to specify those dimensions that are critical for the correct
design of mounting rails and equipment.
The following sections are covered by this document:
– "top hat" section;
– "C" section;
– "G" section.
NOTE 1 Mounting compatibility does not imply functional interchangeability.
Annexes deal with specific steel mounting rails satisfying the requirements of this document,
and give additional dimensional data and loading requirements applicable to such rails.
NOTE 2 The detailed design and material of specific steel rails is given in the annexes.
NOTE 3 Other shapes of rails complying with this document not listed in Annex A can be used.
Mounting rails used as a protective conductor using a conducting connection to a protective
conductor terminal block are specified in IEC 60947-7-2. In other applications where the
mounting rail is used as earthing conductor, the relevant product standard applies.
This document has the status of a horizontal standard in accordance with
IEC Guide 108:2006.
This horizontal standard is primarily intended for use by technical committees in the
preparation of standards in accordance with the principles laid down in IEC Guide 108.
One of the responsibilities of a technical committee is, wherever applicable, to make use of
horizontal standards in the preparation of its publications. The contents of this horizontal
standard will not apply unless specifically referred to or included in the relevant publications.
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 60947-7-2, Low-voltage switchgear and controlgear – Part 7-2: Ancillary equipment –
Protective conductor terminal blocks for copper conductors

– 8 – IEC 60715:2017 © IEC 2017
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
mounting rail
standardized profile of any material used for supporting switchgear, controlgear and
accessories
3.2
reference plane (for measurement)
plane touching the front of the rail
4 Functional requirements
The basic functional requirement of mounting rails is that they shall adequately support
mechanically the electrical equipment.
The rail itself, in combination with the distance between the points of support and the nature
of these supports, shall be of sufficient mechanical strength and stiffness to ensure the
static and dynamic load of the equipment.
Because of the great variety of equipment, and of combinations of equipment, and the spatial
distribution of such equipment, it is not possible to state specific requirements that ensure
proper performance under all conditions; however the detailed dimensions and the strength
requirements given in Annex A and Annex B have been shown by experience to be suitable
for use with a variety of equipment e.g. contactors, fuses, switches, terminal blocks,
accessories and circuit-breakers.
The responsibility for the correct construction and choice of materials lies with the
manufacturer of the complete assembly. Rail mounting affects the performance of equipment,
and it is advisable for product technical committees to give guidance in their publications on
the suitability for mounting on rail.
5 Standard dimensions
5.1 General
Unless otherwise mentioned, dimensions are given in millimetres. Only dimensions and
angles which are critical for the correct design of the rail are specified in Figures 1 to 8.
The indication "burr-free edge" may be made subject to agreement between manufacturer
and user so as to ensure proper fitting in practical cases.

5.2 Top hat section
Reference plane
Reference plane
5,1
1,1
1 ±0,1
10°
R0,4 ±0,1
burr free edges
A
≤3°
≤10°
IEC
IEC
a) Lateral view b) Detail A
Figure 1 – Mounting rail TH 15

Reference plane
7,1
Reference plane
1,04
1 ±0,04
18°
≤R0,2
burr free
A
edges
≤3°
≤18°
IEC IEC
a) Lateral view b) Detail A
Figure 2 – Mounting rail TH 35

3,45
1,8
35,3
15,2
15 ±0,2
35 ±0,3
– 10 – IEC 60715:2017 © IEC 2017
Reference plane
Reference plane
24,6
3 ±0,08
3,08
≤R0,3
burr free edges
6°
A
≤1°
≤6°
IEC IEC
a) Lateral view b) Detail A
Figure 3 – Mounting rail TH 75

In Figures 1 a), 2 a) and 3 a), the cross-hatched area shows the maximum space available for
the rail, its supporting structure and fixing means. The remaining space is the maximum
space which can be counted on as available for the equipment to be mounted on the rail.
Figures 1 b), 2 b) and 3 b) show magnified details of the edge of the rail, including the
manufacturing tolerances. The rails are symmetrical within the given tolerances. The angular
tolerances indicated are one-sided and shall remain between zero and the values indicated.
They include design tolerances.
5.3 "C" section
Reference plane Reference plane
8,15
1,1
A
3°
1 ±0,1
≤3°
IEC
IEC
a) Lateral view b) Detail A
Figure 4 – Mounting rail C 20
0,6 × 45°
9,7
11,5
17,05
75,5
75 ±0,5
11 ±0,3
Reference plane
Reference plane
12,65
1,6
A
3°
1,5 ±0,1
≤3°
IEC
IEC
a) Lateral view b) Detail A
Figure 5 – Mounting rail C 30
Reference plane Reference plane
19,65
6,7
5,5 ±1,2
2,1
A
≤0,5
IEC
IEC
a) Lateral view b) Detail A
Figure 6 – Mounting rail C 40
23,7
0,9 × 45°
14,5
16,5
1,2 × 45°
26,05
35,05
2 ±0,1
18 ±0,5
16 ±0,5
– 12 – IEC 60715:2017 © IEC 2017
Reference plane Reference plane
26,15
8,2
7 ±1,2
3,1
A
≤0,5
IEC IEC
a) Lateral view b) Detail A
Figure 7 – Mounting rail C 50
In Figures 4 a), 5 a), 6 a) and 7 a), the cross-hatched area shows the maximum space
available for the rail and its supporting structure; it does not take into account the fixing
means for the rail. The remaining space is the maximum space which can be counted on as
available for the equipment to be mounted on the rail.
Figures 4 b), 5 b), 6 b) and 7 b) show magnified details of the edge of the rail, including the
manufacturing tolerances. The rails are symmetrical within the given tolerances. The angular
tolerances indicated are one-sided and shall remain between zero and the values indicated.
They include design tolerances.
29,7
20,5
1,8 × 45°
43,05
3 ±0,1
22 ±0,5
5.4 "G" section
Reference plane Reference plane
13,45
6,1
≤3°
1,55
1,5 ±0,05
3°
6 ±0,1
1°
≤1°
A ≤R0,2
Burr free
edge
1,55
1,5 ±0,05
IEC IEC
a) Lateral view b) Detail A
Figure 8 – Mounting rail G 32
In Figure 8 a), the cross-hatched area shows the maximum space available for the rail and its
supporting structure; it does not take into account the fixing means for the rail. The remaining
space is the maximum space which can be counted on as available for the equipment to be
mounted on the rail.
Figure 8 b) shows magnified details of the edge of the rail, including the manufacturing
tolerances. The angular tolerances indicated are one-sided and shall remain between zero
and the values indicated. They include design tolerances.

3,35
1,2 × 45°
16,2
28,6
16,5 –0,3
– 14 – IEC 60715:2017 © IEC 2017
Annex A
(normative)
Specific steel mounting rails
A.1 General
This annex gives specifications for the selection of steel and finish, and specifies the
standards dimension and manufacturing tolerances of specific steel mounting rails which meet
the requirements of this document.
A suitable material is a cold-rolled carbon steel sheet having the following characteristics:
– skin passed after annealing;
– bright surface finish;
2 2
– tensile strength between 320 N/mm and 420 N/mm ;
– elongation at least 30 %;
– 180° bend test horizontally and transversally with regard to the direction of rolling.
A suitable finish is zinc-plating and chromating, with a layer having a thickness of at least
6 µm, except for the cut surfaces resulting from cutting to length.
Other qualities of steel and other finishes may be used by agreement between the
manufacturer and the user.
Unless otherwise stated, dimensions are expressed in millimetres.
The indication "burr free edge" may be made subject to agreement between manufacturer and
user so as to ensure proper fitting in practical cases.
NOTE All symbols in figures are in accordance with ISO 1101.
A.2 Top hat section rail TH 15-5,5
A.2.1 Dimensions
The dimensions stated for such rails are indicated in Figure A.1.
These dimensions apply over the whole length of the top hat but shall not be verified at less
than 10 mm from each end.
5,5 –0,4
Burr free edge
1 ±0,1
0,4 A
R0,2
≤R0,5
A
≤0,3
IEC
Figure A.1 – Top hat rails 15 mm wide for
snap-on mounting of equipment
A.2.2 Tolerances
Mounting rails that are provided as separate components shall respect the additional
tolerances shown in Figure A.2.
2/1 000
2,5/1 000
2,5/1 000
IEC
Figure A.2 – Tolerances (TH 15-5,5)
A.3 Top hat section rail TH 35-7,5 and TH 35-15
A.3.1 Dimensions
Dimensions stated for such rails are indicated in Figure A.3.
These dimensions apply over the whole length of the top hat rail but shall not be verified at
less than 10 mm from the ends.
8,5 ±0,2
15 ±0,2
– 16 – IEC 60715:2017 © IEC 2017
Top hat rail TH 35-7,5 Top hat rail TH 35-15
0 15 –0,4
burr free edge 7,5 –0,4
1 ±0,04
0,6 A
Z
R0,8
15°
R1,2
R0,8
1 ±0,04
R1,2
2,5
A
≤0,3
2,2
Detail Z
IEC
Figure A.3 – Top hat rails 35 mm wide for
snap-on mounting of equipment
A.3.2 Tolerances
Mounting rails that are provided as separate components shall respect the additional
tolerances shown in Figure A.4.
Top hat rail TH 35-7,5 Top hat rail TH 35-15
2/1 000 1/1 000
2/1 000 1/1 000
2/1 000 1/1 000
IEC
Figure A.4 – Tolerances (TH 35-7,5 and TH 35-15)
A.4 Top hat section rail TH 75-25
A.4.1 Dimensions
Dimensions for such rails are indicated in Figure A.5.
These dimensions apply over the whole length of the top hat rail but shall not be verified at
less than 25 mm from the ends.
a
35 ±0,3
a = 27 ±0,2
a = 24 ±0,2
burr free edge
25 –0,4
1 A
R3
R3
A
3 ±0,08 ≤0,3
IEC
Figure A.5 – Top hat rail 75 mm wide for
snap-on mounting of equipment
A.4.2 Tolerances
Mounting rails that are provided as separate components shall respect the additional
tolerances shown in Figure A.6.
1/1 000
1/1 000
1/1 000
IEC
Figure A.6 – Tolerances (TH 75-25)
A.5 "C" section rails: C 20, C 30, C 40 and C 50
A.5.1 Dimensions
Dimensions stated for such rails are indicated in Figure A.7 and Table A.1.
These dimensions apply over the whole length of the "C" section rail but shall not be verified
at less than 10 mm from the ends.
50 ±0,5
75 ±0,5
– 18 – IEC 60715:2017 © IEC 2017
C 20 and C 30 C 40 and C 50
1 A 1 A
R
R
t
≤0,5
s
A s
A
h
h
IEC
Figure A.7 – "C" section rails
Table A.1 – Dimensions of “C” section rails
Type b ± 0,75 h ± 0,75 c R s ± 0,1 t ± 1,2
max
-
C 20 20 10 11 ± 0,3 1 1
-
C 30 30 15 16 ± 0,5 1,5 1,5
C 40 40 22,5 18 ± 0,5 2 2 5,5
C 50 50 30 22 ± 0,5 3 3 7
A.5.2 Tolerance
Mounting rails that are provided as separate components shall respect the additional
tolerances shown in Figure A.8.
2/1 000
2,5/1 000
2,5/1 000
IEC
Figure A.8 – Tolerances (C 20, C 30, C 40 and C 50)
A.6 "G" section rail: G 32
A.6.1 Dimensions
Dimensions stated for such rails are indicated in Figure A.9.
These dimensions apply over the whole length of the "G" section rail but shall not be verified
at less than 10 mm from the ends.
b
c
b
c
1,5 ±0,05
R
6 ±0,1
R
R = 2
+0,5
15 0
IEC
Figure A.9 – Dimensions of "G" section rails
A.6.2 Tolerances
Mounting rails that are provided as separate components shall respect the additional
tolerances shown in Figure A.10.
2,5/1 000
2/1 000 2/1 000
2,5/1 000 2,5/1 000
IEC
Figure A.10 – Tolerances (G 32)

32 ±0,3
16,5 –0,3
– 20 – IEC 60715:2017 © IEC 2017
Annex B
(informative)
Application guide
B.1 General
To determine the permissible load of rails, correctly used, the twisting deflection is always the
most important factor. The sagging stress, on the other hand, is small and can be
disregarded.
When preparing mounting rails for fixing, particular attention should be made about the
possible loss of the rail stiffness and mechanical strength.
B.2 Guidance for use of top hat rails
B.2.1 For steel rails in Annex A
B.2.1.1 General
Research has shown that as a result of the current practice of fixing rails by means of two
screws, a torsion stress τ > 50 N/mm can cause a permanent deflection of the rail. The
maximum permissible torque for that stress is independent of the distance between rail fixing
.
points, for example 750 N mm for a top hat rail TH 35-7,5. For distances between fixing
points used in practice, an excessive deflection occurs generally at this load in the middle of
the top hat rail.
A method for assessing this deflection is shown in Figure B.1.

M
E
L
IEC
Key
M gear torque = weight × distance between the centre of gravity and the mounting plane of the device in
.
N mm (possible supplement to take shock into account)
.
M moment in N mm of the equivalent torque acting in the middle of the rail for a number of individual
E
moments M of similar items of equipment:
∑𝑀
𝑀 =
𝐸
I polar moment of inertia of the rail in mm
E
G sliding modulus (steel plate 80 000 N/mm )
L distance between fixing points
h measure of the deflection of the rail at 50 mm from the fixing surface of the equipment:
𝑀 ×𝐿
𝐸
ℎ = × 50
4 𝐼 ×𝐺
𝐸
Figure B.1 – Assessment of rail deflection
B.2.1.2 Loading of top hat rails
Using this method, the permissible load capacity M , as a function of the distance L between
E
fixing points, has been calculated for three values of deflection h, for both types of rails and is
shown in Figure B.2, for rails TH 35-15 and TH 35-7,5, and in Figure B.3, for rail TH 75-25.
h
– 22 – IEC 60715:2017 © IEC 2017
B.2.1.3 Loading for TH 35-15 and TH 35-7,5 rails
10 000
Permanent deflection of TH 35-15 rail
with τ = 50 N/mm
h = 1,5 mm h = 2 mm
h = 1 mm
5 750
5 000
4 000
3 000
2 000
Permanent deflection of TH 35-7,5 rail
1 000
with τ = 50 N/mm
h = 1 mm h = 1,5 mm h = 2 mm
100 200 300 400 500 1 000 1 500
L  (mm)
IEC
Figure B.2 – Permissible load capacity f(L,h)
M =
E
EXAMPLE 1
.
TH 35-7,5 L = 300 mm may be loaded with M = 330 N mm for h = 1 mm.
E
EXAMPLE 2
It is required to use a rail 800 mm long to support items of equipment having an equivalent torque
.
M = 480 N mm for h = 1 mm.
E
.
First possibility: rail TH 35-15. Figure B.2, shows that L = 800 mm is convenient for M < 2 100 N mm.
E
.
M  (N mm)
E
Rail TH 35-7,5 Rail TH 35-15
.
Second possibility: rail TH 35-7,5. Figure B.2 shows that L = 800 mm is only convenient for M ≤ 120 N mm, but
E
. . .
that L = 400 mm is convenient for M ≤ 250 N mm. As 250 N mm > 480/2 N mm, an intermediate fixing point at
E
L = 400 mm is sufficient.
B.2.1.4 Loading for TH 75-25 rail
Permanent deflection of TH 75-25 rail with τ = 50 N/mm
18 000
h = 1 mm h = 1,5 mm h = 2 mm
16 700
16 000
14 000
12 000
10 000
9 000
8 000
7 000
6 000
5 000
4 000
400 500 600 700 800 900 1 000 1 200 1 400 1 600
L  (mm)
IEC
Figure B.3 – Permissible load capacity M = f(L,h)
E
B.2.2 For rails other than steel rails
For rails of material other than steel, loading data shall be given by the manufacturer in the
form detailed in Figure B.2 and Figure B.3 and based on the methods for assessment of
deflection shown in Figure B.1.
B.3 Guidance for use of "C" section rails
B.3.1 General
To determine the permissible load of rails, correctly used, the twisting deflection is always the
most important factor. The sagging stress, on the other hand, is small and can be
disregarded.
B.3.2 For steel rails to Annex A
B.3.2.1 General
Research has shown that as a result of the current practice of fixing rails by means of two
screws, a torsion stress τ > 50 N/mm can cause a permanent deflection of the rail. The
maximum permissible torque, according to Table B.1 for that stress is independent of the
distance between rail fixing points.
.
M  (N mm)
E
– 24 – IEC 60715:2017 © IEC 2017
Table B.1 – Maximum torque M
max
"C" rail C 20 C 30 C 40 C 50
.
M in N mm 700 2 400 6 400 20 000
max
For distances between fixing points used in practice, with this force, an excessive deflection
occurs generally in the middle of the rail.
A method for assessing this deflection is shown in Figure B.4.
M
E
L
IEC
Key
M gear torque = weight x distance between the centre of gravity and the mounting plane of the device in
.
N mm (possible supplement to take shock into account)
.
M moment in N .mm of the equivalent torque acting in the middle of the rail for a number of individual
E
moments M of similar items of equipment:
∑𝑀
𝑀 =
𝐸
I polar moment of inertia of the rail in mm
E
G sliding modulus (steel plate 80 000 N/mm )
L
distance between fixing points
h deflection of the rail at 100 mm from the fixing surface of the equipment:
𝑀 ×𝐿
𝐸
ℎ = × 100
4 𝐼 ×𝐺
𝐸
Figure B.4 – Assessment of rail deflection
B.3.2.2 Loading of one "C" section rail
Using this method, the maximum permissible torque M , as a function of the distance L
E
between fixing points, has been calculated for the deflection h = 1 mm and is shown in Figure
B.5. For other values of h*, the torque M may be calculated proportionally:
E*
𝑀 ℎ
𝐸
=
∗
𝑀 ℎ
𝐸∗
at any rate without exceeding the value M , to avoid a permanent deflection of the rail.
max
h
In practice, deviations from the theoretical values may occur. Measurements have shown that
the deflection h = 1 mm is reached for moments M shown in Figure B.5, for distances L
E
from 800 mm to 1 000 mm. For shorter distances, the deflection h may be reduced to 0,5 mm
and, for greater distances, increased to 2 mm.
8 000
5 000
C 50
2 000
C 40
1 000
C 30
C 20
200 300 500 1 000 2 000
L  (mm)
IEC
Figure B.5 – Permissible load capacity M = f(L)
E
B.3.2.3 Loading of two "C" section rails
To determine the permissible load capacity of an assembly of two identical "C" section rails,
correctly used, the twisting deflection of the assembly resulting from the horizontal torsion f of
each individual rail is always the most important factor. The vertical deflection, on the other
hand, is small and can be disregarded.
Research has shown that, as a result of the current practice of fixing each rail by two screws,
a torsion stress τ = 50 N/mm can cause a permanent deflection of the rail. The maximum
permissible torque for that stress, according to Figure B.7, is independent from the distance L
between rail fixing points.
A method for assessing the deflection of the assembly is shown in Figure B.6.
.
M  (N mm)
E
– 26 – IEC 60715:2017 © IEC 2017
f
M
E
L
f
IEC
Key
.
M moment in N mm of the equivalent torque acting in the middle of the rail for a number of individual
E
moments M of similar items of equipment:
∑
𝑀
𝑀 =
𝐸
J
moment of inertia of individual rails in mm
E elasticity modulus (steel plate 210 000 N/mm )
L distance between fixing points
H distance between two rails
f deflection of individual rails
h
value of the deflection of the assembly at 100 mm from the fixing surface of the device
Figure B.6 – Assembly of two identical "C" section rails
Assessment of the deflection
Using this method for an assembly with a distance H of 100 mm, the permissible stress M
E
has been calculated and is shown in Figure B.7 as a function of the distance L between
fixing points of rails and for the deflection h = 1 mm.
According to the number, the lateral distance and the quality of the screwed connections
between devices and rails, deflection slightly different from 1 mm can result for the
assembly.
For different distances H*, the permissible stress M and the maximum stress M can be
E* max*
computed by the formula:
𝑀 𝑀 𝐻
𝐸 𝑚𝑚𝑚
= =� �
∗
𝑀 𝑀 𝐻
𝐸∗ max∗
For a smaller or a greater deflection h*, the stress M can be obtained by the ratio:
E*
𝑀 ℎ
𝐸
=
∗
𝑀 ℎ
𝐸∗
still without exceeding the corresponding maximum stress M or M , to avoid any
max max*
permanent deflection of rails.
H
h
B.3.3 For rails other than steel rails
For rails of material other than steel, loading data shall be given in the form detailed in
Figure B.5 and Figure B.7 and based on the methods for assessment of deflection shown in
Figure B.4 and Figure B.6, respectively.
250 000
200 000
C 50
100 000
C 40
50 000
40 000
30 000
C 30
20 000
10 0
...