Cartridge capacitor and method of manufacturing the same

Details Cartridge capacitor and method of manufacturing the same Cartridge capacitor and method of manufacturing the same

1999-04-02

2002-04-02

Reichard, Dean A. (Department: 2831)

Electricity: electrical systems and devices

Electrolytic systems or devices

Liquid electrolytic capacitor

C361S520000, C029S025030

Reexamination Certificate

active

06366445

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates to capacitors. More particularly, the invention relates to capacitors that are rolled into cylindrical cartridges.
A capacitor is a standard passive electronic circuit component including, in its simplest form, two conducting electrodes or plates separated by a dielectric insulator. Capacitors are used in various applications. One common application for capacitors is electric motors. “Motor-start capacitors” are coupled in series to an auxiliary winding of an induction motor and the series circuit of the capacitor and auxiliary winding are used to aid starting the motor and disconnected after a startup period. “Motor-run capacitors” are connected together with an auxiliary winding in parallel to the main winding of an induction motor to boost the power factor of the motor. Generally, motor-run capacitors and motor start capacitors must be quite large and thus are expensive to manufacture.
Electrolytic capacitors include an oxide film as a dielectric. The oxide film is formed by anodically oxidizing an electrode foil made of aluminum, tantalum, titanium, niobium, or the like, to make a “formed” foil and placing the formed foil in opposition to an electrolyte, in the form of a paste for example. The electrolyte can be used as the second electrode or the electrolyte can couple the formed foil to another foil or plate to be used as an electrode. Typically, the formed foil is coated with the electrolyte paste and rolled into a cylindrical cartridge of successive turns. Alternatively, the electrolyte can be impregnated in an absorbent layer, such as a paper layer, by dipping the capacitor cartridge in an electrolyte until the electrolyte is absorbed in the absorbent layer. Because the oxide film is tin, a high capacitance value is realized in a small physical volume. In some motor applications having a short operating cycle, robust electrolytic capacitors are used as motor run capacitors to take advantage of their compact dimensions and lower manufacturing cost.
Floating cathode electrolytic capacitors are known in which an electrically movable “unformed” electrode foil, is disposed between two formed electrode foils and coupled to the formed electrode foils by electrolyte layers. The phrase “formed electrode” as used herein refers to an electrode having an oxide formed thereon by application of an external voltage. The phrase “unformed electrode” as used herein refers to an electrode having only a natural oxide film thereon. The phrase “electrically movable”, as used herein, refers to an electrode that is not directly coupled to any source of electric charge but is charged based only on polarization of other elements in the capacitor. Floating cathode electrolytic capacitors reduce harmful cathodic reactions and deterioration of oxide film properties as compared to standard electrolytic capacitors not having a floating cathode. The general construction of floating cathode electrolytic capacitors is well known. For example, published patent application GB 2056774A discloses an example of a floating cathode electrolytic capacitor.
However, electrolytic capacitors and floating cathode electrolytic capacitors exhibit several limitations. First, such capacitors are not suited for heavy duty type motor-start and motor-run applications because of the extended AC cycle times required in most applications. Specifically, electrolytic capacitors and floating cathode electrolytic capacitors have relatively poor heat dissipation because most portions of the electrodes are covered, i.e. are not on the outside of the cylindrical cartridge. The poor heat dissipation characteristics cause overheating in central portions of the capacitor when used at or near its intended rating, thus causing excess drying in central portions of the capacitor and eventually failure of the capacitor. Because of the limitations noted above, conventional electrolytic capacitors must be oversized for motor applications, even when the operating cycle is short.
SUMMARY OF THE INVENTION
The invention relates to a cartridge capacitor having an increased operating life. A first aspect of the invention is a floating cathode electrolytic capacitor of the type having plural layers superposed on one another and subsequently rolled into a cylindrical cartridge. The capacitor comprises a first layer of an electrolyte material, a second layer of a floating cathode, a third layer of an electrolyte material, and a fourth layer of an anode, constructed of an amorphous oxide foil. The first layer, the second layer, the third layer, and the fourth layer are rolled into a cylindrical cartridge of successive turns.
A second aspect of the invention is a floating cathode electrolytic capacitor of the type having plural layers superposed on one another and subsequently rolled into a cylindrical cartridge. The capacitor comprises a first layer of an electrolyte material, a second layer of a floating cathode, a third layer of an electrolyte material, a fourth layer of an anode, and a conductor coupled to said floating cathode. The first layer; the second layer, the third layer, and the fourth layer are rolled into a cylindrical cartridge of successive turns. The conductor couples turns of the cathode to one another.
A third aspect of the invention is a floating cathode electrolytic capacitor of the type having plural layers superposed on one another and subsequently rolled into a cylindrical cartridge. The capacitor comprises a first layer of an electrolyte material, a second layer of a floating cathode, a third layer of an electrolyte material, and a fourth layer of two anodes, a first of said anodes having an area that is greater than an area of a second of said anodes. The first layer, second layer, third layer, and fourth layer are rolled into a cylindrical cartridge of successive turns. The first of the anodes is disposed in inner turns of the cartridge and the second of the anodes is disposed in outer turns of the cartridge.
A fourth aspect of the invention is a method of manufacturing a floating cathode electrolytic capacitor of the type having plural layers superposed on one another and subsequently rolled into a cylindrical cartridge. The method comprises the steps of providing a first layer of an electrolyte material, providing a second layer of a floating cathode, providing a third layer of an electrolyte material, providing a fourth layer of an anode constructed of amorphous oxide foil, superposing the first layer, the second layer, the third layer, and the fourth layer in order on one another, and rolling the first layer, the second layer, the third layer, and the fourth layer into a cylindrical cartridge of successive turns.
A fifth aspect of the invention is a method of manufacturing a floating cathode electrolytic capacitor of the type having plural layers superposed on one another and subsequently rolled into a cylindrical cartridge. The method comprises the steps of providing a first layer of an electrolyte material, providing a second layer of a floating cathode, providing a third layer of an electrolyte material, providing a fourth layer of two anodes, a first of the anodes having an area that is larger than a second of the anodes, superposing the first layer, the second layer, the third layer, and the fourth layer in order on one another, and rolling the first layer, the second layer, the third layer, and the fourth layer into a cylindrical cartridge of successive turns. The first of the anodes is disposed in inner turns of the cartridge and the second of the anodes is disposed in outer turns of the cartridge.
A sixth aspect of the invention is a method of manufacturing a floating cathode electrolytic capacitor of the type having plural layers superposed on one another and subsequently rolled into a cylindrical configuration. The method comprises the steps of, providing a first layer of an electrolyte material, providing a second layer of a floating cathode, providing a third layer of an electrolyte material, providing a fourth layer of an anode, superposing the first layer

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