Silicone carbide (SiC) wide bandgap (WBG)
materials are one of the most promising solution
to reduce the size and weight of the
power semiconductor modules. Such modules
are able to tolerate high voltages and
currents, temperatures and switching frequencies.
One of the high voltage applications
(10 kV) that they are envisoned to be
widely used in the future is railways. However,
the high operating voltage can be an
obstacle for using WBG-based power modules.
The increased blocking voltage enhances
the local electric field that may become
large enough to induce partial discharges
(PDs) within the SiC module. High
PD activity accelerates the ageing of the
insulating silicone gel, shortening the lifetime
of the whole module dramatically. In
this study, the electrical insulation of 1.2 kV
SiC MOSFET module has been evaluated.
In FEM simulation the highest electric field
strength was seen at the interface between
the silicone gel and the metalized ceramic.
PRPD measurements showed that a surface
discharge was likely to occur at this point.
Lastly, the electric field control methods in
the SiC MOSFET module were proposed.