That sounds interesting, is a SiC power transistor a form of battery storage?
No, it refers to the components that the traction package is built from.
Current packages use power transitors built from silicon, which is the first generation semiconductor on which our civilisation has been built. However practical silicon transistors can only hold off a voltage of ~4-6kV with a single device. This means that attempting to build a 'switch' that can convert 25kV from the overheadline into something useful to the motors has to have numerous devices in series, with all the intendant control problems.
Traditional systems overcome this issue by simply having a transformer between the 25kV supply and the actual bus used b the converter pack, which is often near ~3000V.
However the transformer is enormously heavy.
In contrast, SiC (Silicon carbide) transistors will be able to hold off 15-20kV easily, which means that only two modules in series would be able to switch the 25kV overhead line supply without much difficulty.
For a variety of reasons you would still have a transformer (it has important safety values for example) but since you can put a switch on the 'line' side you can convert the 50Hz supply into one with a frequency of up to 50kHz, potentially allowing you to shrink the transformer's enormous metal 'core' a thousandfold (Actual transformer sizes do not shrink that much as you still have to account for the size of the copper windings which don't shrink).
SO instead of a transformer weighing ten tonnes you get one that weighs something like a hundred kilogrammes, with an additional semiconductor switch of about the same weigh, saving you ~90+% of the weight.
That changes the design choices about the positioning and distribution of the transformers rather drastically.
That may reduce the size of the electric traction package but it isn't going to change the diesel one.
No, but it rather drastically affects the design choices that led to the existing diesel package. No heavy transformer means there is no particular reason to have a Pantograph-transformer trailer vehicle any more.
The Pantograph vehicle can hold the transformer, motors and a diesel engine with ease.
That changes the argument about fewer larger engines versus more smaller ones that would be more compact and easily placeable without causing problems with the floor et al.
The HF transformer also removes any benefit in using a 230/400V 1/3-phase AC supply for auxiliaries, better to use the new data-centre standard of 380V DC which saves further weight in air con and lighting controllers. (1200V SiC MOSFETs also remove the need for a central auxiliary converter on third rail units since you can easily built single level inverters running directly from the third rail).
Its a jump similar to the development of the motor-generator in place of series lighting and voltage dividers.
