A new possibility to improve thermal properties and lifetime of electrical machines is adding some micro-or nano-particles to the epoxy resin and improve the heat dissipation of the machine. This will reduce the temperature in a stator winding. The paper reviews actual work in the field of epoxy materials enriched with aluminum nitride (AlN) or boron nitride (BN). Properties of the particles are described, same as preparation process and influence of usage of coupling agents that creates a bond between particles and epoxy. Brief introduction to the thermal aging of insulation is presented same as influence of the temperature reduction on lifetime of the winding insulation. Further suggestions for improvements and trends are established in discussion.

No abstract

This paper is focused on the determination of thermal parameters (thermal conductivity, thermal diffusivity, and specific heat capacity) of electrical insulating paper from various producers. The transient step-wise method was used to determine all thermal parameters simultaneously. Evaluation was carried out using the differential method. Thermal conductivity was determined from the steady-state temperature response on thickness (corresponding to the number of paper layers), while thermal diffusivity and specific heat capacity was obtained from the dependence of derivative maximum and the corresponding temperature on thickness. Four electro insulating papers differing by composition and thickness: materials NKN (Nomex-Kapton-Nomex), DMD (Dacron-Mylar-Dacron), TFT (TufQUIN TFT 50) and TVAR (ThermaVolt AR) were studied. As a result, the highest value of thermal conductivity (0.17 W/m/K) was determined for the DMD. Remaining three materials possessed thermal conductivity about 0.12 W/m/K. However, differences in specific heat capacity and thermal diffusivity were found to be significantly higher. The lowest specific heat capacity was found for the DMD sample (1200 J/kg/K), while the highest specific heat capacity was found for TVAR sample (4000 J/kg/K).