Application of Power Film Capacitor and Super Capacitor in New Energy Vehicles

This time we discuss some applications of power film capacitors in new energy vehicles.

Most of what I said earlier are some semiconductor devices, which is very important. Among all the devices, in fact, some other devices are still very important. Its product selection and its characteristics are actually very important for your equipment. I will take a few minutes to introduce our company. In fact, the parent company of Redo Electronics is Fujian Torch Electronics. What everyone sees on the exhibition brand is our company. This company has a history of 25 years. It has been nearly 25 years since its establishment. Redo has also been in the trade part for nearly a decade, and long-term cooperation with us are some big international brands. This is the process of the development of Lei Duo Company. It was established in 1999. We have more than 1,000 long-term cooperation customers in the entire China region. This is relatively well-known in the industry and can be regarded as a benchmark. Of our customers, including CRRC and CSR in the craft category, are customers we have been working with for a long time. This is when I took a moment to introduce Redo.

Let me share with you some basic technologies of power film capacitors and application solutions used in new energy vehicles. In fact, what we have seen on the existing new energy vehicles is that most of the control boxes use film capacitors. For film capacitors, the two most common materials are polypropylene and the other. PET. For high-power power electronics, polypropylene materials are widely used. First, the loss value is very low; second, the insulation voltage per unit thickness can be relatively high, which makes a good early technical reserve for product miniaturization; third, the self-healing performance of this material is very good , Its self-healing characteristics are very good. Therefore, on the high-power lithium-ion electronics, polypropylene materials on film capacitors are used very much. Of course, there are many types of this raw material, but this type means that it will be used in different products, and I will not describe them one by one here. Measure the voltage of the product, we know how high a capacity or high voltage may be said to determine a capacitor, then how do we evaluate how high the voltage I need, and for my product how to reach the voltage required by the customer What? For the unit polypropylene film material, its highest voltage is about 600V per micron, and the insulation voltage it can withstand is 600V. In fact, we will not use its limit value when designing power resistance film capacitor , We will use about 200V to 240V, which is based on the customer's product life requirements or temperature requirements will have a range. In this way, it is an aspect to increase the thickness of the film and so on to meet the high voltage requirements of the product. 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. Just mentioned that it has a very good characteristic self-healing performance, self-healing performance is a characteristic of this material itself. When this product is manufactured, we will spray a layer of metallic aluminum on this metalized round film called a round film. It is a vacuum construction method, which may not be perfect. It will have some defects. When this product comes through a relatively large current or voltage, its heat will actively be on the defective film, it will make The aluminum of the metal layer is volatilized. The volatilization process will absorb a lot of heat, which ensures the safety of the entire capacitor product. This feature is called self-healing on the film capacitance of the power electronics. Another good thing about evaporating this point is to form an insulated protective area around the self-healing point, so let this weak point isolate it, so we can see its insulated area and protective area from under the microscope . This is a very important characteristic for the film capacitors of high-power power electronics, which is based on this characteristic. In the future, the use of film capacitors and the market will become wider and wider. And it makes the product's safety and reliability very high.

The self-healing performance I just mentioned does not mean that all overvoltages or overcurrents can play the role of self-healing. If there is too high voltage or too much overvoltage, this This kind of self-healing absorption energy is not enough to absorb all this large energy, it may cause avalanche self-healing, which we call breakdown. In order to prevent this type of avalanche-type self-healing or breakdown, the capacitor manufacturer has another way to avoid it. This technology is called fragmented film or safety film. In fact, there are many types of structure of the segment film or safety film, and only a few are listed in the picture. How does the safety film make the capacitor safer and prevent excessive overcurrent and overvoltage? We can see a schematic diagram of it, this is an interface, you can think of the blue part with metal spray on it, and the white is to remove the metal with the laser. If you have a relatively large amount of energy coming, because the metal area is the smallest in this place, 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 volatilization, the entire area will be isolated and disconnected. It absorbs a lot of heat during the volatilization process, which ensures the safety of the capacitor. We call it the safety film. This is an equivalent circuit diagram of it. In fact, the structure we specially made just now, when the capacitor is put together, if there is a large amount of energy, it will disconnect this place, then this small piece The failure is similar to the failure I just mentioned. This kind of structure is very much in the whole capacitor, tens of thousands, so because of this structure, it can be said that high-power thin film capacitors rarely see very vicious failure or explosion or breakdown.

The other is what we call a non-metallized film capacitor. Its capacity stability is also very high, but there is a very serious defect that it is not self-healing, so its life is uncontrollable, you do n’t Knowing when it will explode or catch fire, etc. This is an older technology. The current high-power thin-film capacitors are metalized thin-film capacitors. We can control the width and size of the segmented film to ensure the attenuation of its capacity. I just mentioned that there are more and more high-power film capacitor application manufacturers. The important reason is that its reliability and life span are very long, because in some industrial markets, such as wind power or new energy vehicles, etc. Among these industries, it has high requirements on product reliability and life. For high-power thin film capacitors, how do we evaluate its life or guarantee its life? If the customer does not have very special requirements, it is a standard design. We will follow three principles:

First, a one-to-one voltage drop means that the voltage of my capacitor products can be equal to the voltage you apply yourself.

Second, the hotspot temperature of 70 degrees. Of course, I will talk about how to evaluate its hotspot temperature, because measuring the reliability of this product is an important parameter.

Third, the lifespan of 100,000 hours.

What I just said is actually some of the problems that our users or customers are most interested in high-power thin-film capacitors, including its safety, reliability and lifespan. Here are some of its product structure. In fact, all film capacitors can't escape these six winding technologies. The first standard winding type is now among many cars including a famous electric vehicle manufacturer in Shenzhen. All products used are in this way. This is a customized round shape, this can be directly placed on the motor, this is done abroad. This flat can be made into a square shape, which can make the volume smaller. This kind of stacking technology is used very much. In many local standard schemes, the film capacitors are made of this type of stacked film capacitors. I have compared these two, one is the characteristics of streamlined square products and laminated products, in fact, the biggest difference between them, the first is the volume ratio, the volume ratio of the laminated type is almost 100 %, It can be said that there is no waste of space in the middle, but in the popular winding, he has corners when winding, so it has a waste of nearly 5% space.

The second difference is that the voltage of the products produced by this popular winding is very high. According to the current technology, the highest voltage of this product can be 100,000 V. The laminated type requires a single film for the film during the manufacturing process. The body needs 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 achieve more than 1000V. These are the two most important differences. For this square film capacitor, the filling technology is nothing more than these three resins, inert gas and oil, which may be mainly resin in new energy vehicles, because of its voltage level and 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 on the structure of the membrane, there are actually internal protections, such as overpressure or overheating protection structures. When we make this product, we will do physical inside. Some protection.