IEC 60034-18-41: a new draft technical specification for qualification and acceptance tests of inverter duty motor insulation

A new International Electro-technical Commission (IEC) Technical Specification (TS) is being developed to define the requirements for qualification of insulation systems to be used in machines supplied by voltage converters. Currently being prepared, it is much more inclusive than NEMA MG-I part 31 (Definite-Purpose Inverter-Fed Polyphase Motors). Once approved, it will significantly influence the development of applicable North American specifications. The TS defines qualification and acceptance tests for inverter duty motor insulation systems It applies to random wound and form wound machines, and contains a very good informative section on drive-related insulation issues. The TS applies to insulation systems for bars and coils in both rotors and stators, but this paper addresses only stator windings. Many manufacturers today are working to develop insulation systems that will meet the stringent requirements of the Technical Specification. This paper presents the highlights of the draft document and how it relates to the current methods of specifying machine insulation systems with non-sinusoidal power supplies. Changes to the way inverter-duty insulation systems are qualified as a result of this specification is discussed and evaluated.