This Part of IEC 60317 specifies the requirements of enamelled round aluminium winding wires of class 200 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-imide 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 200 is a thermal class that requires a minimum temperature index of 200 and a heat shock temperature of at least 220 °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: 0,400 mm up to and including 3,150 mm; – Grade 2: 0,400 mm up to and including 5,000 mm. The nominal conductor diameters are specified in Clause 4 of IEC 60317-0-3.