This part of IEC 60317 specifies the requirements of enamelled rectangular copper winding wire of class 120 with a sole coating based on polyvinyl acetal resin, which may be modified providing it retains the chemical identity of the original resin and meets all specified wire requirements. 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 120 is a thermal class that requires a minimum temperature index of 120 and a heat shock temperature of at least 155 °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 dimensions covered by this standard is as follows: − width: minimum 2,0 mm; maximum 16,0 mm; − thickness: minimum 0,80 mm; maximum 5,60 mm. Wires of grade 1 and grade 2 are included in this specification and apply to the complete range of conductors. The specified combinations of width and thickness as well as the specified ratio width/ thickness are given in IEC 60317-0-2.