Equivalent thermal conductivity determination of winding insulation system by fast experimental approach

One of the main issues to be faced during the implementation of thermal model for electrical machines is the correct selection of some thermal parameters that cannot be computed using analytical equations. The paper is focused on the thermal conductivity of the winding insulation system, which depends on the used insulation materials and on the insulation manufacturing process. A short-time thermal transient test is adopted to evaluate the thermal resistance between winding and stator lamination as well as the equivalent thermal conductivity of the insulation. In addition, the method is extended for evaluating the specific heat of the insulation system. The procedure has been tested on a set of four industrial induction motors with rated power ranging from 1.5 kW up to 4 kW.