Interpretation sheet 2 - Limits and methods of measurement of radio disturbance characteristics of electrical lighting and similar equipment

Provides guidance to assist in selecting a fuse-link to ensure coordination with contactors or motor-starters (contactors with overload relay).[
]The coordination between motor-starters and the fuses which protect them is covered in IEC standards by test requirements such as those in IEC 60947, in particular parts 1 and 4.[
]Overcurrent protection of other equipment, such as motors, conductors, etc., is not covered by this publication.[
]The contents of the corrigendum of February 2001 have been included in this copy.

Feuille d'interprétation 2 - Limites et méthodes de mesure des perturbations radioélectriques produites par les appareils électriques d'éclairage et les appareils analogues

Les informations données sont destinées à faciliter le choix d'un élément de remplacement pour assurer la coordination avec les contacteurs ou démarreurs (contacteurs avec leurs relais de surcharge).[
]La coordination entre les démarreurs et les fusibles qui les protègent est définie dans les normes CEI par les prescriptions d'essais telles que celles de la CEI 60947, en particulier les parties 1 et 4.[
]La protection contre les surintensités d'autres matériels tels que moteurs, conducteurs, etc., n'est pas traitée dans cette publication.[
]Le contenu du corrigendum de février 2001 a été pris en considération dans cet exemplaire.

Low-voltage fuses - Coordination between fuses and contactors/motor-starters - Application guide

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SIST IEC/TR 61459:1998
Low-voltage fuses - Coordination between fuses and contactors/motor-starters -
Application guide
Low-voltage fuses - Coordination between fuses and contactors/motor-starters -
Application guide
Coordination entre fusibles et contacteurs/démarreurs - Guide d'application
Ta slovenski standard je istoveten z: IEC/TR 61459
29.120.50 9DURYDONHLQGUXJD Fuses and other overcurrent
PHGWRNRYQD]DãþLWD protection devices
SIST IEC/TR 61459:1998 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST IEC/TR 61459:1998
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SIST IEC/TR 61459:1998
Première édition
First edition
Fusibles basse tension
Coordination entre fusibles et
Guide d'application
Low-voltage fuses -
Coordination between fuses and
contactors/motor-starters -
Application guide
Copyright – all rights reserved
© CEI 1996 Droits de reproduction réservés –
of this publication may be reproduced or utilized
Aucune partie de cette publication ne peut être reproduite ni No part
in any form or by any means, electronic or mechanical,
utilisée sous quelque forme que ce soit et par aucun procédé,
including photocopying and microfilm, without permission
électronique ou mécanique, y compris la photocopie et les
microfilms, sans l'accord écrit de l'éditeur. in writing from the publisher
Genève Suisse

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Pour prix, voir catalogue en vigueur
For price, see current catalogue
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SIST IEC/TR 61459:1998
1459 ©IEC:1996
1 Scope 7
2 Reference documents 7
3 Definitions 9
4 Criteria for coordination at the rated conditional short-circuit current ly 9
5 Criteria for coordination at the take-over current lc 11
6 Criteria for coordination at the test current "r"
7 Types of coordination
A Test currents and types of coordination
B Fuse-links suitable for motor protection
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SIST IEC/TR 61459:1998
Page 31
Figure B.3
Replace the existing figure by the following new figure:
Fuses used in successful coordination - International results
10 000
Pre-arc I t
Total I t
10 100 1000
Rated current of the fuse I (A)
IEC 196/01
Février 2001 February 2001
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SIST IEC/TR 61459:1998
1459 ©IEC:1996 – 5 –

1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising

all national electrotechnical committees (IEC National Committees). The object of the 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, the IEC publishes International Standards. 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. The IEC collaborates closely with the International Organization

for Standardization (ISO) in accordance with conditions determined by agreement between the two


2) The formal decisions or agreements of the 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 National Committees.

3) The documents produced have the form of recommendations for international use and are published in the form

s or guides and they are accepted by the National Committees in that sense.
of standards, technical repo rt

4) In order to promote international unification, IEC National Committees undertake to apply IEC International

Standards transparently to the maximum extent possible in their national and regional standards. Any

divergence between the IEC Standard and the corresponding national or regional standard shall be clearly

indicated in the latter.

5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any

equipment declared to be in conformity with one of its standards.

6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject

of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.

The main task of IEC technical committees is to prepare International Standards. In

exceptional circumstances, a technical committee may propose the publication of a technical

report of one of the following types:
• type 1, when the required support cannot be obtained for the publication of an
International Standard, despite repeated efforts;

• type 2, when the subject is still under technical development or where for any other

reason there is the future but no immediate possibility of an agreement on an International


• type 3, when a technical committee has collected data of a different kind from that

which is normally published as an International Standard, for example "state of the art".

Technical reports of types 1 and 2 are subject to review within three years of publication to

decide whether they can be transformed into International Standards. Technical reports of

type 3 do not necessarily have to be reviewed until the data they provide are considered to be

no longer valid or useful.

IEC 1459, which is a technical report of type 3, has been prepared by sub-committee 32B: Low-voltage

fuses, of IEC technical committee 32: Fuses.
The text of this standard is based on the following documents:
Committee draft Report on voting
32B/250/CDV 32B/265/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.
Annexes A and B are for information only.
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SIST IEC/TR 61459:1998
1459 © I EC:1996 – 7 –
1 Scope

The information given in this technical report provides guidance to assist in selecting a fuse-

link to ensure coordination with contactors or motor-starters (contactors with overload relay).

The coordination between motor-starters and the fuses which protect them is covered in IEC

standards by test requirements such as those in IEC 947, in particular parts 1 and 4.

Overcurrent protection of other equipment, such as motors, conductors, etc., is not covered by

this standard.

Tests are specified at three levels of prospective current, according to IEC 947-4-1:

a) in the region of the current le (see clause 5). Tests are made at 0,75 /c when the starter

shall disconnect the current without damage and the fuse does not operate, and at 1,25 /c

when the fuse shall operate before the starter (see annex A, figure A.1);

b) at the appropriate value of prospective current "r" shown in IEC 947-4-1, table XI (see

table A.1 in annex A);

c) at the rated conditional short-circuit current lq , if higher than the test current "r".

The fuse selected is capable of absorbing the surge of current on starting the motor and is

normally selected from the recommendations of the manufacturer or by compliance with

national installation codes and wiring rules.

Studies carried out by IEC committee "Fuses" in collaboration with motor-starter manufacturers

worldwide have revealed that there is no major difficulty in achieving satisfactory coordination

at the most exacting of the levels of type of coordination using selected fuses according to

IEC 269-2 in coordination with modern contactors. A survey is presented in annex B of the

rated currents, 1 2t values and cut-off currents of fuses correctly chosen according to the ratings

of the starters they protect, based on the results of successful type testing throughout the


Examples of suitable fuse-links used for motor protection are also given in annex B.

2 Reference documents

IEC 50(441): 1984, International Electrotechnical Vocabulary (IEV) – Chapter 441: Switchgear,

controlgear and fuses

IEC 269-2: 1986, Low-voltage fuses – Pa rt 2: Supplementary requirements for fuses for use by

authorized persons (fuses mainly for industrial application)

IEC 269-2-1: 1987, Low-voltage fuses – Part 2: Supplementary requirements for fuses for use

by authorized persons (fuses mainly for industrial application) – Section 1: Examples of types

of standardized fuses for use by authorized persons
IEC 947: Low-voltage switchgear and controlgear
IEC 947-1: 1988, Low-voltage switchgear and controlgear – Pa rt 1: General rules

IEC 947-4-1: 1990, Low-voltage switchgear and controlgear – Pa rt 4: Contactors and motor-

starters – Section 1: Electromechanical contactors and motor-sta rters
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SIST IEC/TR 61459:1998
1459 ©IEC:1996 – 9 –
3 Definitions

For the purpose of this technical report the definitions in IEC 269-1 apply together with the

following additional definitions:

3.1 switching device (SD): A device designed to make or break the current in one or more

electric circuits. [IEV 441-14-01]
NOTE — A switching device may perform one or both of these operations.

3.2 short-circuit protective device (SCPD): A device intended to protect a circuit or parts

of a circuit against short circuits by interrupting them.
4 Criteria for coordination at the rated conditional short -circuit current lq
Maximum total operating 1 2t and cut-off current

When a fuse is the SCPD being used, /q can be any value up to 50 kA or more. Under these

conditions, the most important parameters are the total let-through 1 2t of the fuse-link (under

the conditions of the three-phase coordination test with the starter in series with the fuse) and

the maximum cut-off current of the fuse.

Values can be provided for all voltage systems and maximum Pt let-through values corresponding to a

test voltage equivalent to the three-phase coordination test (for example: 400 V/ Ird for a 400 V-

three-phase starter) are to be introduced in IEC 269-2-1.

This will also limit the peak cut-off current, because the values are related. However, until

values are introduced in the standard, it can be reported on the basis of international

coordination tests at prospective currents from 50 kA to 200 kA, that at a prospective current of

1p (A), the cut-off current /o (A) of a fuse-link of rated current l„ (A) is equal to or less than the

value given by the formula:
/o = 20
V ln2/p
Guidance for choosing the maximum rated current of an alternative fuse type
From the successful results of coordination type tests at
/q, the sta rter manufacturer can plot

the curves of the maximum total / 2t withstand of the contactor and the overload relay and the

maximum peak let-through current as a function of the rated operational current of the motor-

starter (le). Such a curve is shown in figure la.

A fuse-link of a different type cannot be used without further testing unless its l et and /o values

are equal to or less than the maximum values observed in the tests used to plot the curves.

However, it may be possible to get from the fuse manufacturer data for total / 2t values and

cut-off currents measured under comparable conditions, (i.e. at an equivalent test voltage and

at a prospective current equal to /q). These will be plotted as a function of rated current /n of

the fuse. Typical curves derived from such data are shown for alternative fuses of type A in

figure 1b and for fuses of type B in figure 1c. These have to be plotted on the same scales as

in figure la.
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SIST IEC/TR 61459:1998
–11 –
1459 ©IEC:1996

We have just seen that without further testing we cannot use a fuse with a bigger 1 2t or a

/e = X (amperes) the maximum
bigger cut-off current. Therefore for a starter rated at
2t of

permissible rated current of fuses of type A is seen to be Y (amperes), see figure 1, the 1

rated current Y((amperes) is acceptable, but the cut-off current would be too high. In the case

of replacement fuses of type B, however, the limiting factor is the 1 2t, and Z'(amperes) is

therefore the highest permissible rated current to achieve predictable coordination with the

starter at Iq (see figure 1).

Fuse-link types A and B could be any of the types used for motor circuit protection listed in

annex B.

This procedure may, however, lead to the choice of fuses of excessively low nominal current,

because it does not take into account the additional impedance of the starter (e.g. in case of

association for which the rated operational current of the starter is lower than 10 A, the

overload relay impedance may have a noticeable influence). In such cases, if the additional

impedance is not taken into account to estimate more precisely the prospective short-circuit

er, direct tests will be needed to verify
current and the suitability of the fuses to protect the sta rt

coordination with fuses of higher ratings than determined by the procedure outlined in this

4.3 Further guidance
In addition to the above, the following points should be noted:

High values of clearing time increase the risk of welding of the contacts of the contactor. In

evaluating the "clearing time" for this purpose we consider that the current is "cleared" when it

becomes a small percentage (ca. 5 %) of its limiting peak value. This value may be difficult to

obtain, and an acceptable alternative method is to assume that the limiting curve is a

s) and the peak let-through current
2t (value = [l et] in A2
sinusoidal waveform and from the total 1
teq given by:
(value = I in A) calculate an "equivalent clearing time"
2 x [l2t]
teq =
teq < 5 ms.
A satisfactory value for this equivalent clearing time has been found to be:
, contacts close again while relatively
NOTE – Risk of contact welding increases when, after being thrown apa rt
high arcing currents remain

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