Inverter with large-scale electrolytic capacitors
Used for the large-scale electrolytic capacitor transducer of technical characteristics, analyzed the impact resistance of these capacitors ripple current capacity factor. Through the choice of appropriate materials, and design, make this type parts etc of product performance parameters of the technical index reached completely, and can meet the needs of users.
1 introduction
Frequency conversion technology is stepless motor shall be born of need. Along with the development of power electronic devices, frequency conversion technology is in progress. Since the 1980s, America, Japan, Germany, England etc of VVVF inverter has developed into the market and get the extensive application. At present, inverter has been widely used in power, energy, metallurgy, mine, petrochemical, and other industries high-power fans and pumps etc. The inverter frequency conversion function, it not only creates obvious economic benefit, but also directly to bring greater macro economic benefit and social benefit.
Low-pressure general converter, its main circuit control mode frequency, generally adopted VVVF inverter, the vector control direct torque control frequency and matrix into control frequency into - etc. Besides using matrix were delivered into the control mode, the other three kinds of frequency inverter control mode of the circuit structure are delivered straight - converter. - Their common point is the input power factor, low harmonic current, dc needs large storage capacitance. And matrix converter into - although omit intermediate dc link, eliminating the large size, expensive capacitors. But the technology has yet to mature, cannot be applied. Therefore in the practical use, inverter large-scale electrolytic capacitors to smooth the input voltage inverter circuits.
2 for large-scale electrolytic capacitor transducer technical requirements
The large-scale electrolytic capacitors is used for the smooth filtering, its main technical requirements are as follows:
1) current,
2), small size, are generally capacitors 2/3-3/4,
3) voltage, large capacity, namely high CV value,
4) long life,
5) high reliability and safety.
3 impact resistance of large-scale electrolytic capacitors ripple current capacity factor
Normally ripple current Ir
Ir = (1)
Type: alpha coefficients for cooling,
Δ t for capacitance core temperature and environmental temperature (package temperature),
For the appearance of A capacitor.
From the type of (1), ripple current Ir and become direct ratio. Heat coefficient of alpha, it includes radiation cooling and heat convection, it not only with the product surface temperature, the diameter size, upright, but also related to lie or core covering structure, capacitors, heat conduction in direction, core packages fixed way so closely related.
The equivalent circuit of aluminum electrolytic capacitors
Tan delta = ω CR (2)
Type: R for equivalent series resistance, it is composed of three parts, namely
R = R1 + R2 + R3 (3)
Type: R1 is oxidation film dielectric loss represents the equivalent series resistor,
R3 is conductive plate, and meantime the ohm resistor layer of contact resistance,
R2 is electrolyte represents the equivalent series resistor, namely
R2 = φ ρ d / 2s (4)
Type: φ for electrolytic paper the permeability coefficient,
For the work of the electrolyte ρ Ω resistivity (cm),
D for electrolytic paper thickness (cm),
S for anode geometry size (the foil cm2) appearance.
By above knowable, selecting oxide film analysis of aluminum foil, dielectric loss small selection of permeability coefficient of electrolysis thickness thin little, paper, reduce working electrolyte resistivity and viscosity, improve product structure can obviously reduce the products are tan delta. By reducing the tan, increase the heat delta product, can improve product coefficient of resistance ripple current capacity, so as to ensure products reach long life.
4 the selection of raw materials
Working electrolyte developed 4.1
To meet the big ripple, long service life, high reliability and low resistivity, developed the high voltage, flash fire, forming ability, high performance and stability of new high performance work electrolyte.
4.2 anode foil and selection of electrolytic paper
CDC03 product chooses the high voltage, oxidation film became stable quality and the appropriate hematocrit imported into foil, Choose from NKK company imported high-density, light-weight resistance, high voltage and excellent performance of the paper.
Five core package structure and component design
The structural design of the core covering 5.1
Will foil, using anode evenly to guide lines drawn and special core packages, obviously reduced the structure of the plate and reduce the resistance equivalent series products, thus improving the tan delta resistant ripple current capacity.
5.2 parts design
Design the new flats and aluminium shell. This new flats used better performance of engineering plastics PPS as main material, and USES the compound structure, design the derivation of the nut explosion-proof more excellent, high reliability and consistency of good explosion-proof valve.
6 the hardware
In order to guarantee the products with high reliability, safety and realize the special structure, the core packages company imported advanced large automatic winder and aluminum rivet machine shell, design and manufacture of special aging and aging screening equipment.
7 key technology research, control and guarantee
In aluminum foil cut, to cut the burrs and aluminum foil with strict control dust. New technology is developed and produced rivet pack pack mould. Special rivet The special aging and aging screening process.
8 proposals
1) current electrolytic capacitors quality level of technology has been a qualitative leap for converter, with large-scale electrolytic capacitors, no matter from quality or price and after-sales service, and international similar products to the same caliber, can completely replace the imported products.
2) in converter design, consider appropriately reliability and redundancy design problems, avoid such capacitors early scrapping
