This part of IEC 60317 specifies the requirements of enamelled round copper winding wires of class 120 with a sole coating based on polyvinyl acetal or polyvinyl formal resin, which can be modified provided it retains the chemical identity of the original resin and meets all specified wire requirements. NOTE 1 – 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. NOTE 2 – Polyvinyl acetal is a general name for a family of thermoplastic vinyl resins produced by the condensation of polyvinyl alcohol with an aldehyde. Examples are polyvinyl acetal, polyvinyl formal and polyvinyl butyral. The range of nominal conductor diameters covered by this document is: – Grade 1: 0,040 mm up to and including 2,500 mm; – Grade 2: 0,040 mm up to and including 5,000 mm; – Grade 3: 0,080 mm up to and including 5,000 mm. The nominal conductor diameters are specified in Clause 4 of IEC 60317-0-1:2013.