IEC TR 60943:1998/AMD1:2008

IEC/TR 60943
Edition 2.0 2008-12
TECHNICAL
REPORT
RAPPORT
TECHNIQUE
AMENDMENT 1
AMENDEMENT 1
Guidance concerning the permissible temperature rise for parts of electrical
equipment, in particular for terminals

Guide concernant l’échauffement admissible des parties des matériels
électriques, en particulier les bornes de raccordement

IEC/TR 60943:1998/A1:2008
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IEC/TR 60943
Edition 2.0 2008-12
TECHNICAL
REPORT
RAPPORT
TECHNIQUE
AMENDMENT 1
AMENDEMENT 1
Guidance concerning the permissible temperature rise for parts of electrical
equipment, in particular for terminals

Guide concernant l’échauffement admissible des parties des matériels
électriques, en particulier les bornes de raccordement

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
E
CODE PRIX
ICS 29.020 ISBN 978-2-88910-334-8
– 2 – TR 60943 Amend. 1 © IEC:2008
FOREWORD
This amendment has been prepared by IEC technical committee 32: Fuses.
The text of this amendment is based on the following documents:
DTR Report on voting
32/187/DTR 32/188/RVC
Full information on the voting for the approval of this amendment can be found in the report
on voting indicated in the above table.
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC web site 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• withdrawn;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.
____________
Page 63
Replace the existing Table 6 with the following new table:

TR 60943 Amend. 1 © IEC:2008 – 3 –
Table 6 – Typical values of temperature rise and temperature limits*
Column A Column B
Maximum Maximum
Description of component Remarks
temperature temperature
u
°C
rise K
(Θ = 40 °C)
(Θ = 20 °C)
an
an
Spring Copper and copper alloys

contacts uncoated
p
t 35
– in OG
q
t 75
– in NOG
– in oil 40
t b e
Tinned in OG, NOG , oil 50
b, s b
Nature of Silver- or nickel-plated
a, c, e t t q
contact – in OG or NOG 75
– in oil 50
For contactors, in oil  105 Deterioration of the oil
Bolted Copper, aluminium, and their
connections alloys, uncoated
t q
– in OG 60
q
t
– in NOG
b t
Tinned in OG or NOG 105 Creep point of tin
,
b, s b
Silver- or nickel-plated
t q
– in OG or NOG 75
100 Deterioration of the oil
– in oil
For contactors, in oil 105 Deterioration of the oil
d, f,r
Terminals To be connected to exterior
conductors by screws or bolts
q
Uncoated 60
b
Tinned  105 Creep point of tin
b q
Silver- or nickel-plated 75
g, h
Other contact materials
i
Metallic parts In contact with Insulation class :  Ageing of insulation
Y  90
A 105
E 120
B 130
F 155
H 180
enamel: oil base 100
synthetic 120
j
acting as springs at position of a   Permanent deterioration
k
tin soldering 100 Breaking
l, m
Oil for oil-immersed switchgear 90 Deterioration of the oil
All parts which are metallic or of insulating material in contact with

m
oil, except for contacts
n
Electric motors and resistance
Manual control components  IEC 60364-4-42 :1980
– metallic 55
– non-metallic 65
o
Surfaces Expected to be touched in normal operation but
not to be held continuously in the hand
– metallic 70
– non metallic 80
Accessible, but not designed to be touched in
normal operation
– metallic 80
– non metallic 90
* For notes, see following page.

– 4 – TR 60943 Amend. 1 © IEC:2008
NOTES
a For connection units in vacuum, the limit values of temperature and temperature rise do not apply to the
components in the vacuum. The other components must not exceed the temperature and temperature rise
t
values given in Table 6. Maximum acceptable temperature rises in NOG are the same for silver-plated or
nickel-plated copper as for bare copper, because of the absence of oxygen.
b The following are considered as silver contacts: solid silver contacts, contacts with inlaid silver strips, silver-
plated contacts. In general, for all plated metals, the quality of the plating must be such that a protective layer
remains in the contact zone:
1) after the making and breaking tests (if any);
2) after the permissible short period current test;
3) after mechanical test,
in accordance with the correct specification for each material. If not, the contact must be considered as “bare”.
For nickel-plated contacts, the contact resistance and contact life will be equivalent to those of silver if the
temperature rise is kept within the prescribed limits. This can be achieved by higher contact forces, for
example.
c When engaging parts have different coatings, or one part is of bare metal, the permissible temperatures and
temperature rises shall be:
1) for spring-contacts, those of the surface material having the lowest value permitted in Table 6;
2) for bolted connections, those of the surface material having the highest value permitted in Table 6.
d Values of the tightening torque for screws are given in the appropriate product standard, for example Table IV
of IEC 60947-1:1988.
e For fuses, the temperature rise to be considered can be increased to take into account the proportion of heat
from the fuse element transmitted by conduction to the contacts. Refer to the appropriate specifications for
these components.
f The temperature and temperature rise values are valid even if the conductor connected to the terminals is not
protected by a covering.
g When materials other than those shown in Table 6 are used, their properties shall be taken into consideration.
h Limited by the necessity of not damaging surrounding parts.
i The classification of insulation is given in IEC 60085:1984.
j Temperature shall n
...