Electrolytic capacitor

[0001] This application is a continuation application and claims priority under 35 USC §120 to U.S. patent application Ser. No. 11/966,358, filed on Dec. 28, 2007 (U.S. Pat. No. 7,952,854 to be issued on May 31, 2011), which claims priority to U.S. Provisional Patent Application Ser. No. 60/882,813, filed on Dec. 29, 2006, the entire contents of which are hereby incorporated by reference.

[0002] This disclosure relates to a capacitor. More specifically it relates to a capacitor with multiple capacitor sections selectively connectable to match the capacitance or capacitances of one or more capacitors being replaced.

[0003] One common use for capacitors is in connection with the motors of air-conditioning systems. The systems often employ two capacitors, one used in association with a compressor motor and another smaller value capacitor for use in association with a fan motor. Air-conditioning systems of different BTU capacity, made by different manufacturers or being a different model may use capacitors having different values. These capacitors have a finite life and may fail, causing the system to become inoperative.

[0004] A serviceman making a service call usually does not know in advance whether a replacement capacitor is necessary to repair an air-conditioning system, or what value capacitor or capacitors might be needed for the repair. Often, the serviceman carries a large number of capacitors of different values in the service truck, but it is difficult and expensive to maintain such an inventory, especially because there can be a random need for several capacitors of the same value on the same day. Sometimes, the serviceman returns to the shop or visit a supplier to pick up a replacement capacitor of the required value. This is inefficient as the travel time to pick up parts greatly extends the overall time necessary to complete a repair, and detrimental if there is a backlog of inoperative air-conditioning systems on a hot day. A similar situation may occur is other applications such as refrigeration and heating systems, pumps, and manufacturing systems that utilize compressors.

[0005] By providing a single capacitor adapted to replace any one of a large number of capacitors, a serviceman may carry the capacitor on a service call and, upon encountering one or more failed capacitors, the serviceman can utilize the capacitor to replace the failed capacitor or capacitors.

[0006] In general, the replacement capacitor is connectable to an electric circuit with selectable capacitance values. The capacitor provides multiple capacitance values that may be connected in the field to replace the capacitance value or values of a failed capacitor or capacitors.

[0007] In one aspect, an apparatus is disclosed which includes an electrolytic capacitive element with multiple capacitor sections.

[0008] In another aspect, the disclosure features a system that provides a plurality of selectable capacitance values. The system includes a electrolytic capacitive element that has a plurality of capacitor sections. Each capacitor section has a capacitance value and a capacitor section terminal at a first end. The electrolytic capacitive element has a common element terminal at a second end. The system also includes a plurality of insulated capacitor section wires each connected at one end to a respective section terminal of one of the plurality of capacitor sections, and an insulated common conductor connected at one end to the common element terminal of the capacitor element. The system also includes a case having a side wall, a bottom wall and an open top. The electrolytic capacitive element and the insulated wires and insulated conductor connected thereto are received in the case with the common element terminal adjacent to and insulated from the bottom wall. The system also includes a pressure interrupter cover assembly that includes a deformable cover, a common cover terminal mounted to the deformable cover generally at the center of the cover, a plurality of capacitor section cover terminals mounted to the deformable cover at spaced apart positions generally surrounding the common cover terminal, and connections connecting the terminal post of the common cover terminal to the conductor extending from the common element terminal, and connections respectively connecting the plurality of capacitor section wires to a corresponding terminal post of the plurality of capacitor section cover terminals. The deformable cover has a peripheral edge sealingly secured to an upper end of the case. The common cover terminal has a contact extending upwardly from the cover and a terminal post extending downwardly from the cover to a distal end. Each capacitor section cover terminal has at least two contacts extending upwardly from the cover and a terminal post extending downwardly from the cover to a distal end thereof. Selectable capacitance values are provided by connecting selected cover terminals to place the corresponding capacitor sections in one or more electric circuits and wherein failure of the electrolytic capacitive element causes the deformable cover to deform.

[0009] In another aspect, the disclosure features a system that provides a plurality of selectable capacitance values. The system includes an electrolytic capacitive element having a plurality of capacitors, a plurality of insulated capacitor wires each connected at one end to a respective capacitor terminal of the capacitors, and an insulated common conductor connected at one end to the common element terminal of the electrolytic capacitive element, a case having a side wall, a bottom wall and an open top, and a pressure interrupter cover assembly. Each capacitor has a capacitance value and a capacitor terminal at a first end. The electrolytic capacitive element has a common element terminal at a second end. The electrolytic capacitive element, the insulated wires, and insulated conductor are received in the case with the common element terminal adjacent to and insulated from the bottom wall of the case. The pressure cover assembly includes a deformable cover, a common cover terminal mounted to the deformable cover generally at the center of the cover, a plurality of capacitor cover terminals mounted to the deformable cover at spaced apart positions generally surrounding the common cover terminal, and connections connecting the terminal post of the common cover terminal to the conductor extending from the common element terminal, and connections respectively connecting the plurality of capacitor wires to a corresponding terminal post of the plurality of capacitor cover terminals. The deformable cover has a peripheral edge sealingly secured to an upper end of the case. The common cover terminal has a contact extending upwardly from the cover and a terminal post extending downwardly from the cover to a distal end. Each capacitor cover terminal has at least two contacts extending upwardly from the cover and a terminal post extending downwardly from the cover to a distal end thereof. The selectable capacitance values are provided by connecting selected cover terminals to place the corresponding capacitors in one or more electric circuits and wherein failure of the electrolytic capacitive element causes the deformable cover to deform.

[0010] In another aspect, the disclosure features a system that provides a plurality of selectable capacitance values. The system includes an electrolytic capacitive element having a plurality of capacitors, a plurality of insulated capacitor wires each connected at one end to a respective first capacitor terminal of one of the capacitors, and an insulated common conductor connected at one end to all of the second capacitor terminals of all capacitors, a case having a side wall, a bottom wall and an open top, a pressure interrupter cover assembly, and connections connecting the terminal post of the common cover terminal to the conductor extending from the second capacitor terminals, and connections respectively connecting the plurality of capacitor wires to a corresponding terminal post of the plurality of capacitor cover terminals. Each capacitor has a capacitance value and a first capacitor terminal at a first end of each capacitor and a second capacitor terminal at a second end of each capacitor. The electrolytic capacitive element and the insulated wires and insulated conductor connected thereto are received in the case. The pressure interrupter cover assembly includes a deformable cover, a common cover terminal mounted to the deformable cover generally at the center of the cover, a plurality of capacitor cover terminals mounted to the deformable cover at spaced apart positions generally surrounding the common cover terminal, and connections connecting the terminal post of the common cover terminal to the conductor extending from the second capacitor terminals, and connections respectively connecting the plurality of capacitor wires to a corresponding terminal post of the plurality of capacitor cover terminals. The deformable cover has a peripheral edge sealingly secured to an upper end of the case. The common cover terminal has a contact extending upwardly from the cover and a terminal post extending downwardly from the cover to a distal end. Each capacitor cover terminal having at least two contacts extending upwardly from the cover and a terminal post extending downwardly from the cover to a distal end thereof. The selectable capacitance values are provided by connecting selected cover terminals to place the corresponding capacitors in one or more electric circuits and wherein failure of the electrolytic capacitive element causes the deformable cover to deform.

[0011] In another aspect, the disclosure features a system that provides a plurality of selectable capacitance values. The system includes an electrolytic capacitive element having a plurality of capacitors, a plurality of insulated capacitor wires each connected at one end to a respective first capacitor terminal of the capacitors, and an insulated common conductor connected at one end to all of the second capacitor terminals of all capacitors, a case having a cylindrical side wall, a bottom wall and an open top, a cover assembly, and connections connecting the terminal post of the common cover terminal to the conductor extending from the second capacitor terminals, and connections respectively connecting the other ends of the capacitor wires to a corresponding terminal post of the capacitor cover terminals. Each capacitor has a capacitance value and a first capacitor terminal at a first end of each capacitor and a second capacitor terminal at a second end of each capacitor. The electrolytic capacitive element, the insulated wires, and insulated conductor are received in the case. The cover assembly includes a deformable cover, a common cover terminal mounted to the deformable cover, a plurality of capacitor cover terminals mounted to the deformable cover at spaced apart positions surrounding the common cover terminal. The deformable cover has a peripheral edge sealingly secured to an upper end of the case. The common cover terminal has a contact extending upwardly from the cover and a terminal post extending downwardly from the cover. Each capacitor cover terminal having at least two contacts extending upwardly from the cover and a terminal post extending downwardly from the cover. A first selectable capacitance values between 2.5 microfarads and 10 microfarads and a second capacitance values between 2.5 microfarads to 65 microfarads are provided by connecting selected cover terminals to place the corresponding capacitive sections in one or more electric circuits.

[0012] Embodiments and/or aspects may include any one or more of the following features. The electrolytic capacitive element can be cylindrically wound and the plurality of capacitor sections can be concentric. The system can include an insulating fluid in the case at least partially surrounding the capacitive element. The system can include a cover insulating barrier mounted on the deformable metal cover. The cover insulation barrier has a barrier cup substantially surrounding the cover terminal and a plurality of barrier fins, each extending radially outwardly from the barrier cup and deployed between adjacent section cover terminals. The system can include a rigid disconnect plate supported below the deformable cover. The rigid disconnect plate defines openings accommodating the terminal posts and exposing the distal ends. The system can also include a conductor frangibly connecting the common element terminal of the electrolytic capacitive element to the common cover terminal and conductors respectively frangibly connecting the capacitor section terminals to the section cover terminals. The capacitor sections can have capacitance values in the range of about 2.5 microfarads to about 25 microfarads. The capacitors can have capacitance values in the range of about 2.5 microfarads to about 25 microfarads. The electrolytic capacitive element can include more than five capacitors. The capacitor that have the largest capacitance value can be one of the outer three capacitors of the electrolytic capacitance element. The capacitors can have capacitance values of about 2.5 microfarads, about 5.0 microfarads, about 10.0 microfarads, about 20.0 microfarads, and about 25 microfarads. The electrolytic element can provide dual capacitance values.

[0013] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In case of conflict with any document incorporated by reference, the present disclosure controls.

[0014] Other features and advantages will be apparent from the following detailed description.

[0044] A desirable replacement capacitor would have the electrical and physical characteristics of the failed capacitor, i.e. it should provide the same capacitance value or values at the same or higher voltage rating, be connectable using the same leads and be mountable on the same brackets or other mounting provision. It should also have the same safety protection, for example, as confirmed by independent tests performed by Underwriter Laboratories or others.

[0045] In some applications, the failed capacitor has a relatively high capacitance value, e.g., tens or hundreds of microfarads. In such cases, the replacement capacitor may be an electrolytic capacitor. Electrolytic capacitors generally have higher capacitance values than other types of capacitors.

[0046] Referring FIG. 1a, an electrolytic capacitor 500 includes two electrically conductive material layers 501 and 502 (e.g. aluminum foils, tantalum foils, etc.) that are separated by a dielectric layer 503. For example, as shown, one electrode 501 (the anode) is formed by an aluminum foil. An oxide layer 503 (e.g., Al₂O₃) is built up on the anode layer, thereby providing a dielectric. The counter electrode (the cathode) is a conductive liquid 504 (e.g., an electrolyte). A second aluminum foil 502 (the cathode foil) is placed in electrical contact with the liquid. In typical embodiments, the conductive liquid 504 is provided by placing an electrolyte soaked paper 505 between the anode and the cathode foil, as shown.

[0047] In general, a larger capacitance may be obtained by either increasing the dielectric constant, increasing the electrode surface area, or by decreasing the distance between the electrodes of a capacitor. In typical embodiments, the dielectric oxide layer 503 is formed by performing anode oxidation using electrolysis in an electrolytic solution (note, this electrolytic solution is generally different from the electrolyte used for the conducting fluid of the cathode). Generally, the electrolytic solution is an aqueous solution such as ammonium boric acid or ammonium phosphate. Generally, the thickness of the grown thin film is nearly proportional to the applied voltage used in the electrolysis process. The dielectric properties of the film generally depend on the details of the formations process. The dielectric constant of a typical aluminum oxide layer can range between 7 and 8 times the permittivity of free space.

[0048] As shown in FIG. 1a, in the electrolytic capacitor the conductive liquid 504 flows into intimate contact with the dielectric oxide layer 503 on the anode foil 501, thereby minimizing the distance between the cathode 502 and anode 501.

[0049] The surface area of the anode layer 501 can be increased by roughing the surface using an etching process (e.g., physical etching using an acid such as hydrochloric acid, or electrochemical etching). By roughening the surface of, for example, a high-purity aluminum foil, the effective surface area of aluminum electrolytic capacitors can be increased by as much as 120 times.

[0050] The above described features make it possible to produce electrolytic capacitors with capacitances far larger than those of other types of capacitors.

[0051] FIG. 1b shows a schematic diagram of a wound, multi-section aluminum foil electrolytic capacitive element. Each of the multiple capacitor sections has a capacitance value. One or more of the sections can be connected to an electrical circuit to provide a desired capacitance.

[0052] FIG. 1c shows the capacitive element of FIG. 1b unwound. Aluminum cathode foil 1001 is placed upon nonconductive spacer paper 1002. Electrolyte soaked paper 1003 is placed upon cathode foil 1001. Aluminum anode foil 1004, which includes an oxide layer on its bottom face, is placed on top of electrolyte soaked paper 1003. Anode foil 1004 is cut into sections, thereby forming multiple capacitive sections 1005, 1006, 1007, 1008. Each section includes a distinct anode and dielectric, and all four section share a common cathode. The capacitance of each section depends on, for example, the surface area of the corresponding anode. Thus, capacitive sections can be provided with various desired capacitance values by, for example, cutting the cathode foil strip into sections of varying length.

[0053] Tabs 1009, 1010, 1011, and 1012 are placed in electrical contact with the anode foil of capacitive sections 1005, 1006, 1007, and 1008 respectively. Tab 1013 is placed in electrical contact with cathode foil 1001. For example, in some embodiments the tabs are crimped to the corresponding foil. Although four sections are shown, it is to be understood that more or fewer sections may be provided.

[0054] In some embodiments, it is desirable that each section include an independent cathode. In such cases cathode foil 1001 is cut into sections, as shown in FIG. 1d. Tabs 1013, 1014, 1015, and 1016 are placed in contact with the cathode foils of are placed in electrical connection with the cathode foil of capacitive sections 1005, 1006, 1007, and 1008 respectively.

[0055] In some embodiments, electrolyte soaked paper 1003 may be cut into sections along with the anode and/or cathode foils.

[0056] In general, in various embodiments, the position of the anode and cathode foils can be reversed.

[0057] In some embodiments, electrical connections other than tabs are used. For example, wires may be connected directly to the foils using, e.g. soldering. Although four sections are shown, it is to be understood that more or fewer sections may be provided.

[0058] Referring back to FIG. 1b, in a wound configuration, paper spacer 1002 insulates the capacitor sections from each other. Tabs 1009, 1010, 1011, and 1012 extend beyond the top of wound paper spacer 1002 allowing electrical connection with the anodes of capacitor sections 1005, 1006, 1007, and 1008 respectively. Tab 1013 extends beyond the bottom of wound paper spacer 1002, allowing electrical connection with the common cathode 1001.

[0059] A capacitor 10 is shown in FIGS. 1e, 2 and 3 as well as in other figures to be described below. The capacitor 10 is adapted to replace any one of a large number of capacitors. Therefore, a serviceman may carry a capacitor 10 on a service call and, upon encountering a failed capacitor, the serviceman can utilize the capacitor 10 to replace the failed capacitor with the capacitor 10 being connected to provide the same capacitance value or values of the failed capacitor.

[0060] The capacitor 10 has a wound electrolytic capacitive element 12 of the type described above having a plurality of capacitor sections, each having a capacitance value. The capacitive element 12 is also shown in FIGS. 4 and 5. In an embodiment described herein, the capacitive element 12 has six capacitor sections 20, 21, 22, 23, 24, and 25. As described above, each capacitive element includes an oxide coated anode foil, an electrolyte soaked paper, and a cathode foil, layered upon each other. Separate anodes are provided for each section by, for example, cutting the anode foil into sections as described above. In the pictured embodiment, the capacitor sections share a common cathode. In some embodiments, each capacitor section can have a separate cathode. In certain embodiments, the electrolytic capacitive element 12 has six capacitor sections 20-25. The electrolytic capacitive element 12 is a wound cylindrical element. Accordingly, the capacitive element 12 has a central spool or mandrel 28, which has a central opening 29. An element insulation barrier 30 is provided to separate the six capacitor sections 20-25. In some embodiments, the element insulation barrier corresponds to paper 1002 shown in FIG. 1b. In some embodiments, the element insulation barrier may be insulating polymer sheet material, for example polypropylene.

[0061] With reference to FIGS. 3, 4 and 5, at the lower end of the capacitance element 12, an element common cathode terminal 36 is established by contacting a tab in electrical contact with common cathode foil of the capacitive element to foil strip conductor 38 at 37. In embodiments featuring separate cathodes for each of the multiple capacitor sections, multiple cathode terminals are provided.

[0062] At the top end of the capacitive element 12 as depicted in FIGS. 3, 4 and 5, the element insulation barrier 30 extends above the wound aluminum foils of the capacitor sections. An individual capacitor element section terminal tab is provided for each of the capacitive sections 20-25. The element section terminal tabs are identified by numerals 40-45. Each element section terminal tab is electrical in contact with the anode foil of the corresponding capacitor section. Element section terminals tabs 40-45 are respectively deployed on the capacitor sections 20-25.

[0063] Conductors preferably in the form of six insulated wires 50-55 each have one of their ends respectively soldered to the element section terminal tabs 40-45, as best seen in FIG. 5.

[0064] The insulation of the wires 50-55 is color coded to facilitate identifying which wire is connected to which capacitor section. Wire 50 connected to element section terminal 40 of capacitor section 20 has blue insulation, wire 51 connected to element section terminal 41 of capacitor section 21 has yellow insulation, wire 52 connected to element section terminal 42 of capacitor section 22 has red insulation, wire 53 connected to element section terminal 43 of capacitor section 23 has white insulation, wire 54 connection to element section terminal 44 of capacitor section 24 has white insulation, and wire 55 connected to element section terminal 45 of capacitor section 25 has green insulation. These colors are indicated on FIG. 4.

[0065] The capacitive element 12 is further provided with foil strip conductor 38, having one end attached to the element common cathode terminal 36 at 37. The foil strip conductor 38 is coated with insulation, except for the point of attachment 37 and the distal end 39 thereof. If desired, foil or wire conductors may be utilized for all connections.

[0066] In the capacitive element 12 used in the capacitor 10, the capacitor section 20 has a value of approximately 25.0 microfarads and the capacitor section 21 has a capacitance of approximately 20.0 microfarads. The capacitor section 22 has a capacitance of approximately 10.0 microfarads. The capacitor section 23 has a capacitance of approximately 5.5 microfarads, but is identified as having a capacitance of 5.0 microfarads for purposes further discussed below. The capacitor section 24 has a capacitance of approximately 4.5 microfarads but is labeled as having a capacitance of 5 microfarads, again for purposes described below. The capacitor section 25 has a capacitance of approximately 2.8 microfarads.

[0067] The capacitor 10 also has a case 60, best seen in FIGS. 1-3, having a cylindrical side wall 62, a bottom wall 64, and an open top 66 of side wall 62. The case 60 is formed of aluminum and the cylindrical side wall 62 has an outside diameter of 2.50 inches. This is a very common diameter for capacitors of this type, wherein the capacitor 10 will be readily received in the mounting space and with the mounting hardware provided for the capacitor being replaced. Other diameters may, however, be used, and the case may also be plastic or of other suitable material.

[0068] The capacitive element 12 with the wires 50-55 and the foil strip 38 are received in the case 60 with the element common terminal 36 adjacent the bottom wall 64 of the case. An insulating bottom cup 70 is preferably provided for insulating the capacitive element from the bottom wall 64, the bottom cup 70 having a center post 72 that is received in the center opening 29 of the mandrel 28, and an up-turned skirt 74 that embraces the lower side wall of the cylindrical capacitive element 12 and spaces it from the side wall 62 of the case 60.

[0069] In some embodiments, an insulating fluid 76 is provided within the case 60, at least partly and preferably substantially surrounding the capacitive element 12. The fluid 76 may be the fluid described in U.S. Pat. No. 6,014,308, incorporated herein by reference. The fluid may be one of the other insulating fluids used in the trade, such as polybutene or insulating oil. The fluid may be replaced by other types of insulating materials such as, for example, dielectric greases.

[0070] The capacitor 10 also has a pressure interrupter cover assembly 80 best seen in FIGS. 1-3, 8-10 and 24. The cover assembly 80 includes a deformable circular cover 82 having an upstanding cylindrical skirt 84 and a peripheral rim 86 as best seen in FIGS. 9 and 10. The skirt 84 fits into the open top 66 cylindrical side wall 62 of case 60, and the peripheral rim 86 is crimped to the open top 66 of the case 60 to seal the interior of the capacitor 10 and the fluid 76 contained therein, as shown in FIGS. 1 and 3.

[0071] The pressure interrupter cover assembly 80 includes seven cover terminals mounted on the deformable cover 82. A common cathode cover terminal 88 is mounted generally centrally on the cover 82, and section cover terminals 90-95, each respectively corresponding to one of the capacitor sections 20-25, are mounted at spaced apart locations surrounding the common cover terminal 88. In embodiments featuring separate cathodes for each capacitor section, multiple cathode terminals are provided. With particular reference to FIGS. 1, 2, 9 and 10, the section cover terminal 91 has three upstanding blades 98, 100 and 102 mounted on the upper end of a terminal post 104. Terminal post 104 has a distal end 105, opposite the blades 98, 100 and 102. The cover 82 has an opening 106 for accommodating the terminal post 104, and has a beveled lip 107 surrounding the opening. A shaped silicone insulator 108 fits under the cover in the beveled lip 107 and the terminal post 104 passes through the insulator 108. On the upper side of the cover, an insulator cup 110 also surrounds the post 104, and the insulator cup 110 sits atop the silicone insulator 108; thus, the terminal 91 and its terminal post 104 are well insulated from the cover 82. The other cover section terminals 92-95 are similarly mounted with an insulator cup and a silicone insulator.

[0072] The common cathode cover terminal 88 has four blades 120, and a terminal post 122 that passes through a silicone insulator 112. The common cathode cover terminal 88 mounts cover insulator barrier 114 that includes an elongated cylindrical center barrier cup 116 surrounding and extending above the blades 120 of the common cathode cover terminal 88, and six barrier fins 118 that extend respectively radially outwardly from the elongated center barrier cup 116 such that they are deployed between adjacent section cover terminals 90-95. This provides additional protection against any arcing or bridging contact between adjacent section cover terminals or with the common cathode cover terminal 88. Alternatively, the common cathode cover terminal 88 may be provided with an insulator cup 116, preferably extending above blades 120 but with no separating barrier fins, although the barrier fins 118 are preferred. The terminal post 122 extends through an opening in the bottom of the base 117 of the insulating barrier cup 116, and through the silicone insulator 112, to a distal end 124.

[0073] The pressure interrupter cover assembly 80 has a fiberboard disc 126 through which the terminal posts 122, terminal post 104 and the terminal posts of the other section cover terminals extend. The disc 126 may be also fabricated of other suitable material, such as polymers. The terminal posts 104, 122, etc. are configured as rivets with rivet flanges 128 for assembly purposes. The terminal posts 104, 122, etc. are inserted through the disc 126, insulators 108, 112, insulator cups 110 and barrier cup 116, and the cover terminals 88, 90-95 are spot welded to the ends of the rivets opposite the rivet flanges 128. Thus, the rivet flanges 128 secure the cover terminals 88, 90-95 in the cover 82, together with the insulator barrier 114, insulator cups 110 and silicone insulators 108, 112. The fiberboard disc 126 facilitates this assembly, but may be omitted, if desired. The distal ends of the terminal posts are preferably exposed below the rivet flanges 128.

[0074] The cover assembly 80 has a disconnect plate 130, perhaps best seen in FIGS. 3, 9 and 10. The disconnect plate 130 is made of a rigid insulating material, such as a phenolic, is spaced below the cover 82 by a spacer 134 in the form of a skirt. The disconnect plate 130 is provided with openings accommodating the distal ends of the terminal posts, such as opening 136 accommodating the distal end 105 of terminal post 104 and opening 138 accommodating the distal end 124 of the terminal post 122. With particular reference to FIG. 9, the disconnect plate 130 may be provided with raised guides, such as linear guides 140 and dimple guides 142, generally adjacent the openings accommodating the distal ends of terminal posts. These guides are for positioning purposes as discussed below.

[0075] In capacitor 10, the distal end 39 of the foil strip 38 is connected to the distal end 124 of terminal post 122 by welding. In some embodiments, the conductors between the capacitor sections and the terminal posts are foil strips, such as the one used for the common cathode terminal 36 of the capacitive element 12 herein. The foil strips are positioned on a breaker plate over the distal ends of terminal posts, and are welded to the distal ends of the terminal posts.

[0076] The wires 50-55, in the pictured embodiment, are not well-configured for welding to the distal ends of the terminal posts of the cover section terminals. However, the wires 50-55 are desirable in place of foil strips because they are better accommodated in the case 60 and have good insulating properties, resist nicking and are readily available with colored insulations. In order to make the necessary connection of the wires 50-55 to their respective terminal posts, foil tabs 56 are welded to each of the distal ends of the terminal posts of the section cover terminals 90-95, and the guides 140, 142 are helpful in positioning the foil tabs 56 for the welding procedure. The attachment may be accomplished by welding the distal end of a foil strip to the terminal post, and then cutting the foil strip to leave the foil tab 56. Thereafter, and as best seen in FIGS. 6, 7 and 10, the conductor 58 of wire 50 is soldered to the tab 56, by solder 57. The insulation 59 of wire 50 has been stripped to expose the conductor 58. The other wires 51-55 are similarly connected to their respective cover section terminals. Alternatively, the foil tabs may be soldered to the wires and the tabs may then be welded to the terminal posts, if desired, or other conductive attachment may be employed.

[0077] Accordingly, each of the capacitor sections 20-25 is connected to a corresponding section cover terminal 90-95 by a respective one of color coded wires 50-55. The insulator cups 10 associated with each of the section cover terminals 90-95 are also color coded, using the same color scheme as used in the wires 50-55. This facilitates assembly, in that each capacitor section and its wire conductor are readily associated with the correct corresponding section cover terminal, so that the correct capacitor sections can be identified on the cover to make the desired connections for establishing a selected capacitance value.

[0078] The connections of the wires 50-55 and the foil 38 to the terminal posts is made prior to placing the capacitive element 12 in the case 60, adding the insulating fluid 76, and sealing the cover 82 of cover assembly 80 to the case 60. The case 60 may be labeled with the capacitance values of the capacitance sections 20-25 adjacent the cover terminals, such as on the side of case 60 near the cover 82 or on the cover 82.

[0079] The capacitor 10 may be used to replace a failed capacitor of any one of over two hundred different capacitance values, including both single and dual applications. Therefore, a serviceman is able to replace virtually any failed capacitor he may encounter as he makes service calls on equipment of various manufacturers, models, ages and the like.

[0080] As noted above, the capacitor 10 is expected to be used widely in servicing air conditioning units. Air conditioning units typically have two capacitors; a capacitor for the compressor motor which may or may not be of relatively high capacitance value and a capacitor of relatively low capacitance value for a fan motor. The compressor motor capacitors typically have capacitances of from 20 to about 60 microfarads. The fan motor capacitors typically have capacitance values from about 2.5 to 12.5 microfarads, and sometimes as high as 15 microfarads, although values at the lower end of the range are most common.

[0081] With reference to FIG. 11, capacitor 10 is connected to replace a compressor motor capacitor and a fan motor capacitor, where the compressor motor capacitor has a value of 25.0 microfarads and the fan motor capacitor has a value of 4.0 microfarads. The 25.0 microfarad replacement capacitance for the compressor motor is made by one of the compressor motor leads 160 being connected to one of the blades of the blue section cover terminal 90 of capacitance section 20, which has a capacitance value of 25.0 microfarads, and the other compressor motor lead 161 being connected to one of the blades 120 of common cathode cover terminal 88. The lead 162 from the fan motor is connected to the white section cover terminal 94 of capacitor section 24, and the second lead 163 from the fan motor is also connected to the common cathode cover terminal 88. As set forth above, the actual capacitance value of the capacitor section 24 that is connected to the section cover terminal 94 is 4.5 microfarads, and the instructions and/or labeling for the capacitor 10 indicate that the capacitor section 24 as represented at terminal 94 should be used for a 4.0 microfarad replacement. Preferred labeling for this purpose can be “5.0 (4.0) microfarads” or similar. The 4.5 microfarad capacitance value is within approximately 10% of the specified 4.0 microfarad value, and that is within acceptable tolerances for proper operation of the fan motor. Of course, the capacitor section 24 and terminal 94 may be connected to replace a 5.0 microfarad capacitance value as well, whereby the 4.5 microfarad actual capacitance value of capacitor section 24 gives added flexibility in replacing failed capacitors. Similarly, the 5.5 microfarad capacitor section 23 can be used for either 5.0 microfarad or 6.0 microfarad replacement, and the 2.8 microfarad section 25 can be used for a 3.0 microfarad replacement or for a 2.5 microfarad additive value. FIG. 12 schematically illustrates the connection of capacitor sections 20 and 24 to the compressor motor and fan motor shown in FIG. 11.

[0082] FIG. 13 illustrates another connection of the capacitor 10 for replacing a 60.0 microfarad compressor motor capacitor and a 7.5 microfarad fan motor capacitor. The formula for the total capacitance value for capacitors connected in parallel is additive namely:
C_total=C₁+C₂+C₃+

[0083] Therefore, with reference to FIG. 13, a 60.0 microfarad capacitance value for the compressor motor is achieved by connecting in parallel the section cover terminal 90 (capacitor section 20 at a value of 25.0 microfarads), section cover terminal 91 (capacitor section 21 at a value of 20.0 microfarads), section cover terminal 92 (capacitor section 22 at a value of 10.0 microfarads) and section cover terminal 93 (capacitor section 23 at a nominal value of 5.0 microfarads). The foregoing connections are made by means of jumpers 164, 165 and 166, which may be supplied with the capacitor 10. Lead 167 is connected from the section cover terminal 90 of the capacitor section 20, e.g., to the compressor motor, and lead 168 is connected from the common cathode cover terminal 88, e.g., to the compressor motor. This has the effect of connecting the specified capacitor sections 20, 21, 22 and 23 in parallel, giving a total of 60.0 microfarad capacitance; to with: 25+20+10+5=60. It is preferred but not required to connect the lead from the compressor motor or the fan motor to the highest value capacitor section used in providing the total capacitance.

[0084] Similarly, a 7.5 microfarad capacitance is provided to the fan motor by connecting section cover terminal 94 of the 5.0 microfarad capacitor section 24 and the section cover terminal 95 of the nominal 2.5 microfarad capacitor section 25 in parallel via jumper 169. Leads 170 and 171 connect the fan motor to the common cathode cover terminal 88 and the section cover terminal 95 of the capacitor section 25. FIG. 14 diagrammatically illustrates the connection of the capacitor 10 shown in FIG. 13.

[0085] It will be appreciated that various other jumper connections between section cover terminals can be utilized to connect selected capacitor sections in parallel, in order to provide a wide variety of capacitance replacement values.

[0086] The capacitor sections can also be connected in series to utilize capacitor 10 as a single value replacement capacitor. This has the added advantage of increasing the voltage rating of the capacitor 10 in a series application, i.e. the capacitor 10 can safely operate at higher voltages when its sections are connected in series. As a practical matter, the operating voltage will not be increased as it is established by the existing equipment and circuit, and the increased voltage rating derived from a series connection will increase the life of the capacitor 10 because it will be operating well below its maximum rating.

[0087] With reference to FIG. 15, the capacitor 10 is shown with capacitor section 22 (terminal 92) having a value of 10.0 microfarads connected in series with capacitor section 25 (terminal 95) having a nominal value of 2.5 microfarads to provide a replacement capacitance value of 2.0 microfarads. Leads 162 and 163 make the connections from the respective section cover terminals 92 and 95 to the motor, and the element common cathode terminal 36 connects the capacitor sections 22 and 25 of capacitive element 12. With reference to FIG. 16, the connection of capacitor 10 shown in FIG. 15 is illustrated diagrammatically. In both FIGS. 15 and 16, it will be seen that the cover common cathode terminal 88 is not used in making series connections.

[0088] The formula for capacitance of capacitors connected in series is

[0089] $\frac{1}{C_{\mathrm{total}}}=\frac{1}{C_1}+\frac{1}{C_2}+\frac{1}{C_3}+\dots$

[0090] Therefore, the total capacitance of the capacitor sections 22 and 25 connected as shown in FIGS. 15 and 16 is 2.0 microfarads. The capacitance of each of the capacitor sections 20-25 is rated at 440 volts. However, when two or more capacitor sections 20-25 are connected in series, the applied voltage section is divided between the capacitor sections in inverse proportion to their value. Thus, in the series connection of FIGS. 15 and 16, the nominal 2.5 microfarad section sees about 80% of the applied voltage and the 10.0 microfarad section sees about 20% of the applied voltage. The net effect is that the capacitor 10 provides the 2.0 microfarad replacement value at a higher rating, due to the series connection. In this configuration, the capacitor 10 is lightly stressed and is apt to have an extremely long life.

[0091] With reference to FIG. 17, the capacitor sections of the capacitor 10 are shown connected in a combination of parallel and series connections to provide additional capacitive values at high voltage ratings, in this case 5.0 microfarads. The two capacitor sections 23 and 24 each having a nominal value of 5.0 microfarads are connected in parallel by jumper 177 between their respective cover section terminals 93 and 94. The leads 178 and 179 from a compressor motor are connected to the section cover terminal 92 of capacitor section 22 having a value of 10.0 microfarads, and the other lead is connected to cover section terminal 94 of capacitor section 24. Thus, a capacitance value of 5.0 microfarads is provided according to the following formula

[0092] $\frac{1}{C_{\mathrm{total}}}=\frac{1}{C_1}+\frac{1}{C_2}$

[0093] C₁ is a parallel connection having the value C+C, in this case 5.0+5.0 for a C₁ of 10.0 microfarads. With that substitution, the total value is C_total=5.0 microfarads. The connection of capacitor 10 illustrated in FIG. 17 is shown diagrammatically in FIG. 18.

[0094] FIG. 19 is a chart showing single capacitance values that can be provided by the capacitor 10 connected in parallel. The values are derived by connecting individual capacitor sections into a circuit, or by parallel connections of capacitor sections. The chart should be interpreted remembering that the 2.8 microfarad capacitor section can be used as a 2.5 or 3.0 microfarad replacement, and that the two 5.0 microfarad values are actually 4.5 and 5.5 microfarad capacitor sections, also with possibilities for more replacements.

[0095] FIGS. 20-23 are charts showing applications of capacitor 10 in replacing both a fan motor capacitor and a compressor motor capacitor. This is an important capability, because many air conditioning systems are equipped with dual value capacitors and when one of the values fails, another dual value capacitor must be substituted into the mounting space bracket.

[0096] The chart of FIG. 20 shows dual value capacitances that can be provided by capacitor 10 wherein the nominal 2.5 microfarad capacitor section 25 is used for one of the dual values, usually the fan motor. Fan motors are generally not rigid in their requirements for an exact capacitance value, wherein the capacitor section 25 may also be used for fan motors specifying a 3.0 microfarad capacitor. The remaining capacitor sections 20-24 are available for connection individually or in parallel to the compressor motor, providing capacitance values from 5.0 to 65.0 microfarads in 5.0 microfarad increments.

[0097] The chart of FIG. 21 also shows dual value capacitances that can be provided by capacitor 10. In the chart of FIG. 21, one of the dual values is 5.0 microfarads that can be provided by either capacitor section 23 having an actual capacitance value of 5.5 microfarads or by capacitor section 24 having an actual capacitance of 4.5 microfarads. As discussed above, the capacitor section 24 can also be used for a 4.0 microfarad replacement value, and capacitor section 23 could be used for a 6.0 microfarad replacement value. Thus, chart 21 represents more dual replacement values than are specifically listed. The other capacitor section may be used in various parallel connections to achieve the second of the dual capacitance values.

[0098] The chart of FIG. 22 illustrates yet additional dual value capacitances that can be provided by capacitor 10. Capacitor section 25 (nominal 2.5 microfarads) is connected in parallel with one of capacitor section 23 (5.5 microfarads) or capacitor section 24 (4.5 microfarads) to provide a 7.5 microfarad capacitance value as one of the dual value capacitances. The remaining capacitor sections are used individually or in parallel to provide the second of the dual value capacitances.

[0099] The chart of FIG. 23 illustrates yet additional dual value capacitances that can be provided by capacitor 10, where capacitor section 22 (10 microfarads) is dedicated to provide one of the dual values. The remaining capacitor sections are used individually or in parallel for the other of the dual values.

[0100] It will be appreciated that any one or group of capacitor sections may be used for one of a dual value, with a selected one or group of the remaining capacitor sections connected to provide another capacitance value. It will also be appreciated that the capacitor 10 could provide six individual capacitance values corresponding to the capacitor sections, or three, four or five capacitance values in selected individual and parallel connections. Additional single values can be derived from series connections.

[0101] The six capacitor sections 20-25 can provide hundreds of replacement values, including single and dual values. It will further be appreciated that if fewer replacement values are required, the capacitor 10 can be made with fewer than six capacitor sections, and that if more replacement values were desired, the capacitor 10 could be made with more than six capacitor sections

[0102] While specific values for the capacitance of the capacitor sections are given above, it is to be understood that different values may be provided. For example, some air conditioning systems include so-called “motor-start” capacitors with typical capacitances in the range of 30 microfarads to 300 microfarads. Such capacitors are typically used during start-up periods. In some embodiments, capacitor 10 is a replacement capacitor for a “motor-run” capacitor. The capacitance values for capacitance sections 20-25 are about 22.5 microfarads, about 33.0 microfarads, about 40.0 microfarads, about 45.0 microfarads, about 70.0 microfarads, and about 90 microfarads, respectively. The color of white terminal 94 is changed to purple to indicate that corresponds to a capacitor section with a different capacitance value than that of terminal 93. The chart of FIG. 24 illustrates a number of single vale capacitances that can be provided by capacitor 10. For example, as shown in column g, the 70 microfarad, 45 microfarad, and 22.5 microfarad capacitor sections can be connected in parallel as described above to provide a single capacitance vale of 107.5 microfarads. In other embodiments, capacitance values for capacitance sections 20-25 are about 20 microfarads, about 30 microfarads, about 55 microfarads, about 67 microfarads, about 70.0 microfarads, and about 83 microfarads, respectively.

[0103] In various embodiments, capacitor 10 can provide single, dual, or multiple capacitance values over a variety of ranges. In some embodiments, capacitor 10 may provide capacitance values of, for example, up to 300 microfarads or more or about 400 microfarads or more. Capacitor 10 can also include capacitor sections with a variety of voltage ratings, thereby providing a suitable replacement for a range of capacitors with different operating voltages.

[0104] There are occasional failures of capacitive elements. If the capacitive element fails, it may do so in a sudden and violent manner, producing heat and outgassing such that high internal pressures are developed within the housing. Pressure responsive interrupter systems have been designed to break the connection between the capacitive element and the cover terminals in response to the high internal pressure, thereby removing the capacitive element from a circuit and stopping the high heat and overpressure condition within the housing before the housing ruptures.

[0105] The pressure interrupter cover assembly 80 provides such protection for the capacitor 10 and its capacitive element 12. With reference to FIG. 25, the capacitor 10 is shown after failure. Outgassing has caused the circular cover 82 to deform upwardly into a generally domed shape. When the cover 82 deforms in the manner shown, the terminal posts are also displaced upwardly from the disconnect plate 130, and the weld connection of the distal end 124 of common cathode cover terminal post 122 to the distal end 39 foil lead 38 from the common cathode element 36 of the capacitive element 12 is broken, and the welds between the foil tabs 56 and the terminal posts 104 of the section cover terminals 90-95 are also broken, the separation at section cover terminals 91 and 94 being shown.

[0106] Although the preferred pressure interrupter cover assembly includes the foil lead 38 and foil tabs 56, frangibly connected to the distal ends of the terminal posts, the frangible connections both known in the art and to be developed may be used. As an example, the terminal posts themselves may be frangible.

[0107] It should be noted that although it is desirable that the connections of the capacitive element and all cover terminals break, it is not necessary that they all do so in order to disconnect the capacitive element 12 from a circuit. For all instances in which the capacitor 10 is used with its capacitor sections connected individually or in parallel, only the terminal post 122 of common cathode cover terminal 88 must be disconnected in order to remove the capacitive element 12 from the circuit. Locating the cover common terminal 88 in the center of the cover 82, where the deformation of the cover 82 is the greatest, ensures that the common cover terminal connection is broken both first and with certainty in the event of a failure of the capacitive element 12.

[0108] If the capacitor sections of the capacitor 10 are utilized in a series connection, it is necessary that only one of the terminal posts used in the series connection be disconnected from its foil tab at the disconnect plate 130 to remove the capacitive element from an electrical circuit. In this regard, it should be noted that the outgassing condition will persist until the pressure interrupter cover assembly 80 deforms sufficiently to cause disconnection from the circuit, and it is believed that an incremental amount of outgassing may occur as required to cause sufficient deformation and breakage of the circuit connection at the terminal post of one of the section cover terminal. However, in some applications of the capacitor 10, the common cover terminal 88 may be used and the central location of the common cover terminal 88 may cause fast and certain disconnect upon any failure of the capacitive element.

[0109] Two other aspects of the design are pertinent to the performance of the pressure interrupter system. First, with respect to series connections only, the common cover terminal 88 may be twisted to pre-break the connection of the terminal post 122 with the foil strip 38, thus eliminating the requirement of any force to break that connection in the event of a failure of the capacitive element 12. The force that would otherwise be needed to break the connection of common terminal post 122 is then applied to the terminal posts of the section cover terminals, whereby the section cover terminals are more readily disconnected. This makes the pressure interrupter cover assembly 80 highly responsive in a series connection configuration.

[0110] Second, the structural aspects of welding foil tabs to the distal ends of the terminal posts corresponding to the various capacitor sections and thereafter soldering the connecting wires onto the foil tabs 56 is also believed to make the pressure interrupter cover assembly 80 more responsive to failure of the capacitive element 12. In particular, the solder and wire greatly enhance the rigidity of the foil tabs 56 wherein upon deformation of the cover 82, the terminal posts break cleanly from the foil tabs 56 instead of pulling the foil tabs partially through the disconnect plate before separating.

[0111] A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention.

[0112] For example, although the above described embodiments employ electrolytic capacitor sections of the foil type, other types of capacitor sections may be used including tantalum electrolytic, electrolytic double-layer, or aerogel.

[0113] In some embodiments, one or more capacitor sections may be a non electrolytic capacitor section. For example, capacitor 10 could include capacitor sections which are of the ceramic type, silver mica type, plastic film type, tantalum type, and/or polyester film type. In some embodiments, the capacitor sections may include a combination of capacitor types.

[0114] Various types of electrical connections may be used. For example, the foil strip used to connect the common cathode terminal of capacitor element 12 to the common cathode cover terminal 88 may be replaced by an insulated wire. Various electrical contacts may be provided by any method including, for example, crimping, soldering and/or welding.