This part of IEC 60034 describes thermal endurance test procedures for classification of
insulation systems used in a.c. or d.c. rotating electrical machines with indirect cooling and
form-wound windings.
The test performance of a candidate insulation system is compared to the test performance of
a reference insulation system with proven service experience.
The test procedures described in IEC 60034-18-31 are intended to compare the thermal
endurance performance of the mainwall insulation between conductor(s) and ground and,
where required by the design of the coil or bar, the insulation between the turns.
The test is not intended to simulate the in-service mechanical stresses experienced by the
endwinding bracing or support materials. It does not include the evaluation of thermomechanical
deterioration by expansion and contraction of insulation during temperature
cycling.
IEC 60034-18-1 describes general testing principles applicable to thermal endurance testing
of insulation systems used in rotating electrical machines. The principles of IEC 60034-18-1
are followed unless otherwise stated in IEC60034-18-31.
The thermal class for the insulation system refers to its maximum allowed (“hot spot”)
temperature. The average temperature measured in service should not exceed the allowed
temperature rise according to IEC 60034-1.