Application of power film capacitors and ultracapacitor in new energy vehicles (II)

The self-healing properties I've just talked about don't really mean that all overvoltages or overcurrents can act as self-healing. If too high a voltage or too high an overvoltage comes, the self-healing energy can't be absorbed enough to absorb all of this energy, it can cause avalanche. Self healing, we call it breakdown. To prevent this avalanche-type self-healing or breakdown, the capacitor manufacturer has another way to avoid it, a technique we call a fragment film or a safety film. In fact, there are a lot of structural types of fragment film or safety membrane. How can the safety membrane be realized to make the capacitor safer and prevent overcurrent and overpressure? We can see a schematic diagram of it. It's an interface. The blue part you can think of is sprayed with metal. The white part is stripped of metal with a laser. If you have more energy coming in, because the metal area is the smallest in this place, so this place has the greatest current density, so most of the heat is concentrated in this place. If the amount of heat accumulated reaches a certain level, he will volatilize the aluminum above, which will cause the entire area to be isolated and disconnected. It absorbs a great deal of heat during the evaporation process to ensure the safety of capacitors, which we call the safety film. This is an equivalent circuit diagram. Actually, as I said earlier, we made this structure deliberately. When the capacitors put it together, if a large amount of energy comes in and disconnects this place, then this small piece will fail, just like what I said earlier. This structure is very large in the entire capacitor, thousands of them, so it is because this structure can be said that high-power thin-film capacitors rarely see very malignant failure or explosion or breakdown.

The other is what we call a non-metallic film capacitor, which has a high stability of capacity, but there is a very serious defect that it is not self-healing, so its life is uncontrollable, you do not know when it will explode or ignite combustion, and so on, this is a relatively old technology. Today's high-power thin-film capacitor is metallized thin-film capacitor, we can control the width and size of its fragments to ensure its capacity decline. I just mentioned that more and more high-power thin-film capacitors are being used. The important reason is that their reliability and lifetime are very long, because in some industrial markets, such as wind power or new energy vehicles and so on, their reliability and lifetime requirements are very high. For high-power thin-film capacitors, how do we evaluate their life or ensure their life, if the customer does not have very special requirements that is standard design, we will follow three principles:

One to one voltage drop means that the voltage of my capacitor product can be equal to that of your own application.

The 70 degree hot spot temperature, of course, I'll talk about how we evaluate the hot spot temperature, because measuring the reliability of this product hot spot temperature is an important parameter.

One hundred thousand hours of life.

What I've just talked about is actually some of the issues that our users or customers are most interested in about high-power thin-film capacitors, including their safety, reliability, and lifetime. Let's talk about some of its product structure. In fact, all thin-film capacitors, nothing more than to escape these six winding technology, the first standard winding, now in many cars, including Shenzhen, a very famous electric car manufacturer, he uses this way of products. This is a custom-made circular, this can be directly set on the motor, this is done abroad. The flat can be made into squares and can make the volume smaller. This stacking technique is very versatile, and in many local standard schemes the membrane capacitor is chosen to be made of this type of laminated film capacitor. I have compared the two, one is the streamlined winding square products and laminated products, in fact, the biggest difference between them, the first is the volume ratio, laminated volume ratio is almost 100%, it can be said that there is no waste of space in the middle, but the popular winding, he winding edges and corners so it There is a waste of nearly 5% space.

The second difference is that this popular winding produces products with very high voltage. The highest voltage of this product can reach 100,000 V by current technology. The laminated winding has to cut the film monomer during the manufacturing process, so there will be some damage. Its voltage is not very high now, it should be. In 630V, there are also more than 1000 V, which are the two most important differences. For this square-shaped thin-film capacitor, the technology now filling is nothing more than these three resins, inert gases and oils, which may be resin-based in new-energy vehicles, because the new-energy vehicles its voltage level and power levels are not very large, compared to other applications in the industrial market for its voltage level. And power are relatively small. In fact, in each filling technology, in addition to the structural protection of the membrane, there is actually internal protection, such as pressure or overheating protection structure, we do this product in the interior of some physical protection.