Efficiency of power inverters in electric/hybrid vehicles

[Ryuk1990]

I am interested in increasing the range of electric/hybrid vehicles. Increasing the energy density of batteries is something chemists, materials scientists, and chemical engineers worry about.

What about from the electrical side though? Can electrical engineers do much to significantly increase range?

Although I am an EE student, I have not taken any classes in power electronics yet so I may no be accurate with what I'm about to say. I could not find any specific numbers on efficiency of power inverters but typically, power inverters reach about 90% (maybe even more) efficiency at their rated power level. Correct?

Now could power inverters ever become extremely efficient (without the use of superconductivity) to the point that they will have greater than 90% efficiency at various power levels? Driving speeds are dynamic and therefore the electric motor(s) require all sorts of power levels depending on the speed and acceleration of the vehicle.

 

[Windadct]

The invertter alone can / should be better then 90% - the losses in the inverter are due to conduction losses - and switching losses. The higher the switching frequency ( not the output freq) the higher the switching losses. There are benefits to high switching frequency - better quality power to the motor ( lower losses, longer life), less filtering ( lower cost, and lower losses in the filter) etc.
So the whole system design is a matter of trade offs.

In the inverter - there is primarily the improvements in the semiconductors ( MOSFETs, IGBTs and Diodes) - but this is incremental, and to a certain extent the module ( packaging ) design to improve cooling, module life, etc- but the mechanical design does have some effect on losses ( The devices have lower losses when they are cooler - for example). There are semiconductors on the horizon like silicon carbide ( which is actually a very old semiconductor technology) - but due to cost / benefit not a lot of commercial use today - but they do look promising for reducing the losses.
Lastly - there is the vehicle market, which has its own expectations - exp for life time.

The key IMO is still better batteries - with only a 30% improvement in energy density/cost/life time - the equation for vehicles will look competitive with gas fueled.