铝电解电容器应用手册

铝电解电容器应用手册

Application Guide This Application Guide

This guide is a full handbook on aluminum electrolyticapplication for the major aluminum electrolytic types capacitors, of course with emphasis on Cornell made worldwide. We encourage you to tell us what more Dubilier’s types. It covers construction in depth and you’d like to know, so we can improve this guide.discloses the latest information on performance and

Aluminum Electrolytic Capacitor Overview

Except for a few surface-mount technology (SMT) alu-minum electrolytic capacitor types with solid electro-lyte systems an aluminum electrolytic capacitor con-sists of a wound capacitor element, impregnated with liquid electrolyte, connected to terminals and sealed in a can. The element is comprised of an anode foil, paper separators saturated with electrolyte and a cathode foil. The foils are high-purity aluminum and are etched with billions of microscopic tunnels to increase the surface area in contact with the electrolyte.

They are polar devices, having distinct positive and neg-ative terminals, and are offered in an enormous va-riety of styles which include molded and can-style SMT devices, axial and radial-leaded can styles, snap-in ter-minals styles and large-can, screw terminal styles. Rep-resentative capacitance-voltage combinations include

330 µF at 100 V and 6800 µF at 10 V for SMT devices

100 µF at 450 V, 6,800 µF at 50 V and 10,000 µF at 10 V for miniature-can styles,1200 µF at 450 V and 39,000 µF at 50 V forsnap-in can styles and

9000 µF at 450 V and 390,000 µF at 50 V forlarge-can, screw-terminal styles.

While it may appear that the capacitance is between the two foils, actually the capacitance is between the anode foil and the electrolyte. The positive plate is the anode foil; the dielectric is the insulating aluminum oxide on the anode foil; the true negative plate is the conductive, liquid electrolyte, and the cathode foil merely connects

to the electrolyte.

This construction delivers colossal capacitance because

etching the foils can increase surface area more than 100 times and the aluminum-oxide dielectric is less than a micrometer thick. Thus the resulting capacitor has very large plate area and the plates are awfully close together.

If two, same-value, aluminum electrolytic capacitors are connected in series, back-to-back with the positive ter-minals or the negative terminals connected, the result-ing single capacitor is a non-polar capacitor with half the capacitance. The two capacitors rectify the applied voltage and act as if they had been bypassed by diodes. When voltage is applied, the correct-polarity capacitor

These capacitors routinely offer capacitance values from gets the full voltage. In non-polar aluminum electrolytic 0.1 µF to 3 F and voltage ratings from 5 V to 550V. capacitors and motor-start aluminum electrolyte capaci-tors a second anode foil substitues for the cathode foil to

achieve a non-polar capacitor in a single case.

Capacitor Construction

Rilled

Construction

CDM Cornell Dubilier 140 Technology Place Liberty, SC 29657 Phone: (864)843-2277 Fax: (864)843-3800 http://

铝电解电容器应用手册

Application Guide Capacitor Construction

Lead Wire

Terminal

RubberTopDiscPhenolicDisc

AluminumTabsRubber

AluminumTabsCapacitorElementTape

SleeveCanCapacitorElement

CanSleeve

as much as 100 times for foil in low-voltage capacitors and 20 to 25 times for high-voltage capacitors. Forming

The anode foil carries the capacitor’s dielectric. The di-electric is a thin layer of aluminum oxide, Al2O3, that is chemically grown on the anode foil during a process called “formation.” Formation is accomplished by pull-ing the anode foil on rollers through an electrolyte bath and continuously applying a DC voltage between the bath and the foil. The voltage is 135% to 200% of the nal capacitor’s rated voltage. The thickness of the alu-minum oxide is about 1.4 to 1.5 nm for each volt of the formation voltage, e.g., the anode foil in a 450 V capacitor may get a formation voltage in excess of 600 V and have an oxide thickness of about 900 nm. That’s less than a hundredth the thickness of a human hair.

Miniature,

Radial-Leaded Type

Snap-in Type

Formation reduces the effective foil surface area be-cause the microscopic tunnels are partially occluded by the oxide. The tunnel etch pattern is adjusted by choice of foil and etching process so that low-voltage anodes have dense tunnel patterns compatible with thin oxide and high-voltage anodes have coarse tunnel patterns

Conventional Cornell Dubilier

compatible with thick oxide. The cathode foil is not

Construction Thermal Pak

formed and it retains its high surface area and dense

These gures show typical constructions of the etch pattern.non-surface-mount aluminum electrolytic capacitors.

Most Cornell Dubilier capacitors use compression- t Slittingconstruction so there is no thermoplastic potting com-Foil is etched and formed in jumbo rolls of 40 to 50 cm

pound to interfere with safety-vent operation. Thermal

wide and then slit into various widths according to the

Pak and Rilled are Cornell Dubilier’s unique con-lengths of the nal capacitors.

structions for computergrade, screw terminal capaci-tors. Compared to conventional, potted construction, Windingthey operate cooler, provide longer life, withstand

higher shock and vibration, deliver more reliable safe-The capacitor element is wound on a winding machine

with spindles for one-to-four separator papers, the an-ty vent operation and are lighter weight.

ode foil, another set of one- …… 此处隐藏：62947字，全部文档内容请下载后查看。喜欢就下载吧 ……