IEC TR 61624:1997 pdf download – Guidance on the development of listsof maximum allowable temperaturesfor polymeric compounds used in electrotechnical equipment

IEC TR 61624:1997 pdf download – Guidance on the development of listsof maximum allowable temperaturesfor polymeric compounds used in electrotechnical equipment.
This technical report gives guidance to technical committees wishing to develop lists of maximum allowable temperatures for polymei*c compounds under normal and abnormal operating conditions.
It discusses and makes recommendations concerning:
a) the factors which influence the choice of an appropriate method of describing polymeric compounds, bearing In mind the complex recipes of many compounds and the resulting wide ranging properties (see 5.1);
b) the factors which influence the selection of data for inclusion in lists of maximum allowable temperatures for polymeric compounds under normal operating conditions (see 5.2 and 5-3):
C) lists for the maximum allowable temperatures for polymeric compounds under abnormal operating conditions (see clause 6).
In this report the term •temperature is used, although it is realized that it is customary to use temperature rise for practical reasons. One may be converted into the other, given an appropriate reference point, e.g. 25 C.
2 NormatIve references
The following normative documents contain provisions which, through reference In this text. constitute provisions of this technical report. At the time of publication, the editions indicated were valid- All normative documents are subject to revision, and parties to agreements based on this technical report are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. Members of IEC and ISO maintain registers of currently valid International Standards.
lC 60216 Guide for the aeterminalion of thermal endurance properties of electrical insulating materials (being revised)
IEC 60335-1: 1991, Safety of household and similar electrical appliances — Part 1: General requirements
IEC 60695-2-1/0: 1994. Fire hazard testing — Part 2: Test methods — Section 1/sheet 0: Glow- wire test methods — General
lEG 60695-2-1)1: 1994, Fire hazard testing — Part 2: Test methods — Section 1/sheet 1: Glow- wire end-product test and guidance
IEC 60695-2-1/2: 1994. Fire hazard testing — Part 2: Test methods — Section 1/sheet 2: Glow- wire flammability test on materials
IEC 60707: 1981. Methods of test for the determination of the flammability of solid electrical insulating materials when exposed to an igniting source
ISO 75-2: 1993. Plastics — Determination of temperature of deflection under load — Part 2:
Plastics and ebonite
ISO 178: 1993, Plastics — Determination of flexural properties
3.4 long term: A period of time of the same magnitude as the expected operational life of the equipment, for example for household appliances, in the range 50 h to 8 000 h.
3.5 short term: A period of time that is much less than the expected operational life of the equipment.
3.6 general electrotechnical applications: Use of an electrotechnical product in an environment, where the predominant type of long-term degradation 01 the product is the result of thermally activated chemical reactions.
4 General discussion
41 Background
The plastics industry worldwide manufactures upwards of one million different polymeric compounds, many of which find use in electrotechnical equipment as moulded. cast or machined parts.
The range and magnitude of temperature/time exposure over which these parts may be used are dependent upon the properly levels that have to be retained for safe storage, handling and use. The properties of these types of materials change with time and temperature with the rate of change also being dependent on temperature. The different properties may change at different rates. Frequently the mode of use and the local environmental conditions also lead to additional stresses which have an effect on the useful life 01 the materialsiparts.
A number of IEC committees have used normative lists of maximum allowable temperatures for parts made of insulating materials under normal operation for many years with apparent success and safety. However, these lists consisted of data for either products manufactured to other IEC standards which gave limiting conditions of use, or parts based on recognized and proven insulation systems, for example motor windings, o insulating materials of the thermosetting type. Thermoplastic insulating materials were specifically excluded from these lists.