This part of IEC 60317 specifies the requirements of enamelled round copper winding wire of class 180 with a dual coating. The underlying coating is based on polyester or polyesterimide resin, which may be modified providing it retains the chemical identity of the original resin and meets all specified wire requirements. The superimposed coating is based on polyamide resin. NOTE A modified resin is a resin that has undergone a chemical change, or contains one or more additives to enhance certain performance or application characteristics. Class 180 is a thermal class that requires a minimum temperature index of 180 and a heat shock temperature of at least 200 °C. The temperature in degrees Celsius corresponding to the temperature index is not necessarily that at which it is recommended that the wire be operated and this will depend on many factors, including the type of equipment involved. The range of nominal conductor diameters covered by this standard is as follows: – grade 1: 0,050 mm up to and including 3,150 mm; – grade 2: 0,050 mm up to and including 5,000 mm; – grade 3: 0,250 mm up to and including 1,600 mm. The nominal conductor diameters are specified in Clause 4 of IEC 60317-0-1.