This article discusses some applications of power film capacitors in new energy vehicles.

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Most of the previous ones are some semiconductor devices, which are very important. In all devices, in fact, some other devices are still very important. Its product selection, its characteristics are good or bad, in fact, the impact on your equipment is also very important. I will take a few minutes to introduce our company. In fact, the parent company of Leidu Electronics is Torch Electronics of Fujian. Everyone sees our company on the exhibition sign. This company has a history of 25 years. Founded until now nearly 25 years. Leidu has also been in the trade for nearly a decade, and long-term cooperation with us is some of the major international brands. This is the development process of Leidu Company. It was established in 1999. We have more than 1,000 long-term cooperation customers in the whole of China. This is quite famous in the industry, and they can all be called benchmarks. Our customers, in the craft category including North and South, are our long-standing customers. This is what I spent a little time introducing the company.

Let me share with you some basic technologies of power film capacitors and applications for new energy vehicles. In fact, we have seen that in the existing new energy vehicles, most of its control boxes use film capacitors. For film capacitors, the most common two materials, one is polypropylene, the other is PET. For high-power power electronics, polypropylene materials are used extensively. First, the loss value is very low. Second, the insulation voltage that the unit thickness can withstand is relatively high, which makes a good technical reserve for the miniaturization of the product volume. Third, the self-healing performance of this material is very good. Its self-healing features are very good. Therefore, on the high-power lithium battery, the polypropylene material on the film capacitor is used very much. Of course, there are many types of such raw materials, but this type, that is, it will be used in different products, not described here. Measuring the voltage of the product, we know that determining a capacitor may say how high or how high the voltage is, so how do we evaluate how high the voltage I need, how to reach the voltage that the customer needs for my product. What? For a unit of polypropylene film material, its current maximum voltage is about 600V, and the insulation voltage that can withstand is 600V. In fact, we will not use its limit when designing the power resistor film capacitor. We will use between about 200V and 240V, depending on the customer's requirements for product life or temperature requirements. In this way, increasing the thickness of the film and the like to achieve the high voltage requirement of the product is one aspect. Second, if the voltage is too high, I may have some structure in series in the capacitor to increase the voltage.

For high-power power electronic film capacitors, it uses polypropylene. It has just been mentioned that it has a very good self-healing property, and self-healing properties are a property of the material itself. When this product is manufactured, we will spray a layer of metallic aluminum on the metallized film called the round film. It is a way of vacuum construction, it may not be perfect, it will have some defects. When the product comes over a relatively large current or voltage, its heat will actively be on the defective film, it will make this The aluminum of the layer metal volatilizes, and the volatilization process absorbs a large amount of heat, which ensures the safety of the entire capacitor product. This characteristic is called self-healing on the membrane capacitance of power electronics. Another good thing to volatilize this point is to form an insulating protection zone around the self-healing point. Let's say that this weak point isolates it, so we can see its insulated area and protected area from under the microscope. . This is an important characteristic for the membrane capacitors of high-power power electronics. Based on this characteristic, the range and market of membrane capacitors will become wider and wider in the future, and many of them are based on this self-healing performance. And it makes the product's safety and reliability very high.

The self-healing performance I just talked about is actually not that all overvoltage or overcurrent can play this self-healing effect. If there is too high voltage or too much overvoltage, this The self-healing energy is not enough to absorb all of this large energy, it may cause avalanche-like self-healing, which we call breakdown. In order to prevent this avalanche-type self-healing or breakdown, the capacitor manufacturer has another way to avoid it. This technique is called a fragment film or a safety film. In fact, there are many types of structure of the segment film or the security film, and only a few are listed in the picture. How does the safety film make the capacitor safer and prevent excessive overcurrent and overpressure? We can look at the graphics of a principle, this is an interface, you can think that there is a metal spray on the blue part, and the white one is to use a laser to remove the metal. If you have a relatively large amount of energy coming in, because in this place, its metal area is the smallest, so the current density is the largest in this place, so most of the heat is concentrated in this place. If the accumulation of heat reaches a certain level, he will volatilize the aluminum above, and after evaporation, the entire area is isolated and disconnected. It absorbs a lot of heat during the volatilization process, ensuring the safety of the capacitor, which we call a safety film. This is an equivalent circuit diagram. In fact, I just said that we have done this kind of structure. When the capacitor is put together, if there is a big energy coming over, this place will be disconnected. It is invalid, it is similar to the failure I just mentioned. This structure is very numerous among the entire capacitors, tens of thousands, so it is because of this structure that high-power film capacitors rarely see very vicious failure or explosion or breakdown.

The other is what we call a non-metallized membrane capacitor. Its capacity is also very stable, but there is a very serious flaw. It is not self-healing, so its life is uncontrollable, you are not at all Knowing when it will explode or burn, etc., this is an older technology. Today's high-power film capacitors are metallized film capacitors. We can control the attenuation of its capacity by controlling the width and size of its segment film. I have just mentioned that there are more and more application manufacturers of high-power film capacitors. The important reason is that its reliability and longevity are very long, because in some industrial markets, like wind power or new energy vehicles, etc. Among these industries, it has high requirements for product reliability and longevity. For high-power film capacitors, how do we evaluate its life or ensure its life? If the customer does not have very specific requirements, it is a standard design, we will follow three principles:

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

Second, the 70-degree hot spot temperature, of course, I personally talk about how we evaluate its hot spot temperature, because measuring the reliability of this product hot spot temperature is an important parameter.

Third, 100,000 hours of life.

What I just said is actually some of the problems that our users or customers are most interested in in their high-power film capacitors, including its safety, reliability and longevity. Here are some of its product structure. In fact, all the film capacitors are nothing more than the six winding technologies that can't escape. The first standard winding type is now among many manufacturers of electric cars including Shenzhen's famous electric car. The products used are all in this way. This is a custom round shape, which can be placed directly on the motor. This is what foreign countries do. This flat shape can be made into a square shape, which can make the volume smaller. This lamination technique is used in many ways, and in many local standard schemes, the film capacitors are selected by this stacked film capacitor. I have compared the two types, one is the product of the streamlined winding and the characteristics of the stacked product. In fact, the biggest difference between them is that the first one is the volume ratio, and the stacked volume ratio is almost 100. %, it can be said that there is no waste of space in the middle, but the popular winding, he has angular edges when winding, so it has a waste of nearly 5% space.

The second difference is that the voltage produced by this popular winding is very high. According to the current technology, the highest voltage of this product can reach 100,000 V. The laminated type requires a single film in the manufacturing process. The body has to be cut, so there will be some damage. Its voltage is not very high now. It should be at 630V, and some people can do more than 1000V. This is the two most important differences. For this kind of square-shaped film capacitor, the technology of filling now is nothing more than these three kinds of resin, inert gas and oil. In new energy vehicles, it may be resin-based, because of the voltage level of new energy vehicles. The power is not very large, and its voltage level and power are relatively small compared to other applications in the industrial market. In fact, in every filling technology, in addition to the protection of the structure of the membrane, there is actually internal protection, such as over-pressure or overheating protection structure. We will do physical work inside when we do this product. Some protection.

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