IEC 61858 pdf download Electrical insulation systems – Thermal evaluation of modifications to an established wire-wound EIS
5 Evaluation of the change of thickness of an EIM
5.1 Samples Representative samples of the established EIS (the reference EIS) and of the EIS with reduced EIM thickness(es) (the candidate EIS) shall be evaluated in accordance with Clause 1 0.
5.2 Acceptance A candidate EIS that meets the acceptance criteria according to Clause 1 0 shall be assigned the same thermal class as the established EIS. If the results of the candidate EIS testing are outside the acceptance criteria according to Clause 1 0, then full thermal ageing in accordance with IEC 61 857-1 shall be conducted in order to establish its thermal class. NOTE Full thermal ageing may be accomplished by testing at additional temperatures, according to IEC 61 857-1 .
6 Substitution of winding wire
6.1 General Substitution of a winding wire evaluated in the established EIS can be made without additional testing when one or more of the following conditions have been met:
a) the winding wire conforms to an IEC 6031 7 specification having the same chemical composition, according to the Annex A groupings, as the winding wire evaluated in the established EIS but is of a different size or shape;
b) the winding wire conforms to an IEC 6031 7 specification having the same chemical composition, according to the Annex A groupings, as the winding wire evaluated in the established EIS and has an equal or higher thermal class;
c) the winding wire is a bare conductor insulated with one of the EIM evaluated as part of the established EIS in accordance with IEC 61 857-1 . The thickness to be used shall be such that the electrical stress per unit thickness is not greater than the stress to which the EIM was subjected during the ageing test.
NOTE For substitution of an alternate EIM, refer to Clause 8.
6.2 Substitution of enamel For chemical composition substitution criteria, refer to Annex A.
6.3 Substitution of conductor material An established EIS, which has been evaluated with copper as the conductor, may use either copper or aluminium conductor. An established EIS, which has been evaluated with aluminium as the conductor, may use either aluminium or copper conductor, provided the thermal performance of the substitute winding wire has been established to be equal to or better than the winding wire evaluated.
6.4 Alternate winding wire Winding wires that do not meet the criteria in 6.1 or 6.2 shall be evaluated in accordance with IEC 61 857-1 . Examples would include either bondable winding wire, conductor insulated with an EIM not included in the established EIS, or lead wire used as an alternate winding wire.