Components and System
NREL researchers work to advance power electronics technologies for vehicle components and systems, including power switches, capacitors, and active filters—key components in an inverter.
Power Switch Research
NREL focuses on improving power switches in inverters. The goal is to have a power switch stage that can run a variety of motors and loads. Our engineers and scientists are developing new methods to cool insulated gate biopolar transistors (IGBTs) power switches to more effectively run adjustable speed motors with variable loads. IGBTs are viewed as an effective type of power switch for advanced vehicle power electronic applications. They are controlled electronically by low-power signals.
Capacitor and Active Filter Research
Capacitors account for a major fraction of the weight, volume, and cost of an inverter. NREL experts research and evaluate the performance of capacitors used in motor drives. NREL has developed capacitor testing capabilities, including thermal cycling and accelerated reliability techniques, to test prototypes from industry and other laboratories.
Currently, electrolytic aluminum capacitors are used for voltages lower than 450 V, but they are bulky, have no tolerance for high temperatures, little tolerance for ripple current, short lifetimes, and sometimes fail catastrophically. Two promising alternatives to electrolytic aluminum are polymer-film capacitors and ceramic capacitors. Polymer-film capacitors are used for voltages higher than 450 V and are more streamlined than electrolytic aluminum capacitors, but they also cannot tolerate high temperatures. Research has identified several candidate polymers with higher-temperature capabilities. Further DOE research will look at scaleup and manufacturing technologies, as well as ceramic capacitors, which have the greatest potential for volume reduction and the best ability to tolerate high temperatures. The emphases for ceramic capacitors will be on ensuring a benign failure mode and lowering costs.
NREL is also investigating the potential for active filters to replace passive capacitors. These active filters may have several advantages in the inverter thereby improving motor performance levels and increasing battery or fuel cell lifetimes.