Effect of Titania Nanofiller on Electrical Tree of Silicone Gel

Silicone gel is used for an encapsulating material in power electronic modules. However, the voltage endurance of silicone gel is substantially reduced due to the generation of an electrical tree, which refers to a deterioration involving internal cavities that spread similar to trees. In this study, we investigated the breakdown voltage of silicone gel caused by electrical treeing (treeing breakdown voltage) and the suppression of treeing due to the addition of nanofillers to the silicone gel. To evaluate the breakdown voltage, we constructed needle-plane electrodes molded with a silicone gel. Breakdown tests revealed that the breakdown voltage of the silicone gel depended on the rate of increase of the applied voltage
$(\mathrm{V}_{\mathrm{r}\mathrm{a}\mathrm{t}\mathrm{e}})$
. The breakdown voltage of the silicone gel with added
$\text{TiO}_{2}$
nanofillers (NC) was compared to that of neat silicone gel at
$\mathrm{V}_{\mathrm{r}\mathrm{a}\mathrm{t}\mathrm{e}}=10\text{kV}_{\mathrm{p}\mathrm{e}\mathrm{a}\mathrm{k}}/\mathrm{s}$
. It was observed that NC had a higher breakdown voltage than neat silicone gel. Furthermore, optical microscope observation revealed that the development of electrical trees in the silicone gel was suppressed by the addition of TiO2 nanofillers. These results indicate that the addition of
$\text{TiO}_{2}$
nanofillers to silicone gel can enhance the treeing breakdown voltage.