New High Temperature Capacitor For Electric Vehicles

28th August 2013
Jacqueline Regnier

Hybrids and pure electric vehicles rely on high efficiency power conversion and management. The power electronics found in these vehicles require cooling because of limitations in the temperature rating of components such as capacitors, which are used to store electrical energy. This in turns adds weight to the vehicles and drags down their reliability and efficiency.

>Researchers at the National Physical Laboratory (NPL) in the UK have developed a new lead-free, high temperature ceramic capacitor that could improve efficiency and reliability of electric vehicles. Announced in August 2013, the new ceramic capacitor called HITECA (high temperature capacitor) is made of a dielectric material with a high energy density that can run at high temperatures and is capable of reducing cooling needs for hybrid and electric car controls. The new capacitors from NPL reduce the need for cooling and the associated weight of the vehicles. Besides, its high permittivity enables smaller electronic devices and reduces the loss of capacitance with voltage. Also, the new ceramic capacitor dielectric material offers stable capacitance at temperatures of 200 °C and above, while the current technology is restricted to operating at temperatures around 150 °C. The study has been funded by the UK Technology Strategy Board program for Low Carbon Vehicles.
The researchers explored different compositions and different ways of fabricating them. They measured current at a range of high temperatures using advanced measurement techniques. The most promising materials were optimized to achieve the desired properties. The resulting capacitor is created from a ceramic, based on doped-BiFeO3 compound. Other types of capacitors, for example barium titanate capacitors, can lose up to 85% of their capacitance at working voltage. HITECA also manages to outperform other ceramic chip capacitors in temperature range, lower temperature capacitance change, and lower voltage capacitance change.It can be a breakthrough in automotive power electronics, which according to NPL, represents an emerging $61bn global market. Tatiana Correia, who led the work at NPL, said: "Industrial electronics needs to be able to perform in harsh environments in which they operate. The ability of HITECA capacitors to function at higher temperatures than existing capacitors will help make electronic systems more robust and remove barriers for technologies such as electric vehicles that rely on them," said Tatiana Correia, who led the work at NPL. "The opportunities for electric vehicles are huge, both financially and environmentally, but they are currently being held back by a few technical issues. With this high temperature capacitor we believe we have solved an important one of those issues and will play a vital part in the move towards mass market electric vehicles."

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