BS IEC 61624:1997 pdf download – Guidance on the development of lists ofmaximum allowabletemperatures for polymeric compoundsused in electrotechnical equipment

BS IEC 61624:1997 pdf download – Guidance on the development of lists ofmaximum allowable temperatures for polymeric compounds used in electrotechnical equipment.
This technical report gives guidance to technical committees wishing to develop lists of maximum allowable temperatures for polymeric 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 JEC and ISO maintain registers of currently valid International Standards.
IEC 60216. (;uide for the determination 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.
IKC 60695.2.1/0:1994. Fire hazard testing — Part 2: Test methods — Section 1/sheet 0: Glow.wire test methods — General.
IEC 60695.2-1/1:1994, Fire hazard testing Part 2: Test methods — Section 1/sheet 1: Glow-wire end.product test and guidance.
3.6
general electrotechn ical applications use of an electrotechnical product in an environment, where the predominant type of long-term degradation of the product is the result of thermally activated chemical reactions
4 General discussion
4.1 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 ternperatureltirne exposure over which these parts may be used are dependent upon the property 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 heing 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 of the materials/parts.
A number of IKC 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 IKC standards which gave limiting conditions of use, or parts based on recognized and proven insulation systems, for example motor windings, or insulating materials of the thermosetting type. Thermoplastic insulating materials were specifically excluded from these lists.
Part.s made from thermoplastic materials were required to he tested separately with requirements being based on actual temperatures that had been measured during normal and abnormal operation. The question has now to be asked whether these lists can be safely extended to include thermoplastic materials as well as a wider selection of thermosetting types.