That ability to absorb and release energy quickly is what makes capacitors so useful in power electronics applications, including the drive systems of electric vehicles. Large capacitors perform multiple functions in modern electric vehicles. They smooth the flow of energy through the circuits that convert direct current from the battery to alternating current at the motor, for example.
And they can act as a buffer at times of high demand, absorbing excess energy during regenerative braking or discharging to boost acceleration. Making capacitors that perform well in electric mobility applications is tricky. The storage capacity of a device is closely related to the area of its conductive plates, but engineers need compact, robust components they can easily integrate into their designs. One way to do that is to make the plates and insulating layer from thin, flexible materials that can be rolled up into a small package.
Today’s component makers are taking that approach to extremes. Ultra-thin film capacitors, which are common in automotive applications, use oriented polypropylene (OPP) or polyester (PET) films as their insulators. “In automotive applications, we see film thicknesses down to 1.2 micrometers,” says Michael Mücke, Head of R&D and Product Management for Bühler Leybold Optics’ Flexible segment, the part of the business that makes the machines that apply coatings of conductive material onto the insulator material.