This test procedure specifies, in accordance with the provisions of IEC Publication 216-1, a method for evaluating the temperature index of round enamelled winding wires. It is not applicable to rectangular winding wires or to fibre-insulated winding wires. In order to avoid undue fragility of the test specimens, experience has shown that sizes from 0.8 mm to 1.5 mm are generally found convenient to handle and test.