Large aluminum electrolytic capacitors for inverters - News - Global IC Trade Starts Here.

SMD aluminum electrolytic capacitor

Photocoupler

Where: α is the heat dissipation coefficient;
Δt is the difference between the temperature of the capacitor core package and the ambient temperature (temperature rise);
A is the external surface area of ​​the capacitor.

Just proportional. The heat dissipation coefficient α, which includes radiation heat dissipation and convection heat dissipation, is not only related to the temperature difference, diameter, upright or horizontal position of the product surface, but also to the core package structure, the heat conduction inside the capacitor, the heat flow direction, and the core package fixing method. So closely related.
It is known from the equivalent circuit of aluminum electrolytic capacitor
Tanδ=ωCR(2)
Where: R is the equivalent series resistance, which consists of three parts, ie
R=R ₁ +R ₂ +R ₃ (3)
Where: R ₁ is the equivalent series resistance represented by the dielectric loss of the oxide film;
R ₃ is the ohmic resistance of the plate, the conductive layer, and the contact resistance therebetween;
R ₂ is the equivalent series resistance represented by the electrolyte, ie
R ₂ = φ·ρ·d/2s(4)
Where: φ is the permeability coefficient of the electrolytic paper;
ρ is the resistivity of the working electrolyte (Ω·cm);
d is the thickness (cm) of the electrolytic paper;
s is the apparent geometry (cm ² ) of the anode foil.
It can be seen from the above analysis that the selection of the aluminum foil with a small loss of the dielectric film of the oxide film, the selection of the electrolytic paper having a small permeability coefficient and a small thickness, the reduction of the resistivity and viscosity of the working electrolyte, and the improvement of the product structure can significantly reduce the tan δ of the product. By reducing tan δ and increasing the heat dissipation coefficient of the product, the ability of the product to withstand ripple current can be improved, thereby ensuring that the product has a long life requirement.
4 selection of raw materials
4.1 Development of working electrolyte In order to meet the requirements of large ripple current, long life and high reliability, a new high-performance working electrolyte with low resistivity, high flashover voltage, strong forming ability and stable high temperature performance was developed.
4.2 Selection of anode foil and electrolytic paper
The CDC03 type product adopts imported into a foil with high formation voltage, stable oxide film quality and proper specific volume; it has selected high-density, thin-type and high-voltage-resistant electrolytic paper with high comprehensive performance imported from NKK.

5-core package structure and component design
The design of the 5.1 core package structure divides the anode foil evenly, adopts multiple pairs of lead strips and special core package structure, which significantly reduces the equivalent series resistance of the electrode plate and reduces the tan δ of the product, thereby improving the product resistance. The ability to wave current.
5.2 Parts are designed with a new cover and aluminum housing. The new cover plate uses the better performance polyphenylene sulfide engineering plastic as the main material, and adopts the composite structure of the extraction nut to design an explosion-proof valve with better explosion-proof performance, high reliability and good consistency.
6 Hardware Protection In order to ensure high reliability, safety and special core package structure, Cinda has invested heavily in the introduction of large-scale automatic riveting machine and aluminum shell sealing machine, designed and manufactured for special aging and aging. Filter the device.
7 Research, control and guarantee of key processes The cutting burrs and aluminum foil dust are strictly controlled when the aluminum foil is cut. A new riveting process was developed and a special riveting die was made. Special aging and aging screening processes have been developed.
8 Product test situation and user usage According to the above analysis, select the appropriate anode foil and electrolytic paper, impregnate the new working electrolyte, use the newly designed components, and use the special manufacturing process to produce CDC03 400V10000μFφ90×157 products. The test conditions are detailed in Table 4.
9 recommendations
1) At present, the technical quality level of China's aluminum electrolytic capacitors has undergone a qualitative leap. For large-scale aluminum electrolytic capacitors for inverters, it has been indistinguishable from similar foreign products in terms of quality, price and even after-sales service. product.
2) When designing the inverter, it is recommended to properly consider the reliability and redundancy design issues to avoid early failure of such electrolytic capacitors.