A variable vacuum capacitor is described in which oil inside the main bellows (21) is pumped through the bellows and through the oil circuit (8) of a heat exchanger by a pump (15). Water passes through coolant channels (6) of the heat exchanger, from inlet (7) to outlet (7′). The extendable capacitor drive shaft (14) is hollow and serves as a conduit, conveying the oil to the bottom of the (bellows 21), thereby ensuring a full circulation of the oil right through the bellows and then through the heat exchanger. Pump drive means (9) may be a gerotor hydraulic motor, coupled to a gerotor oil pump (15) via magnetic coupling (22). Pumping heat transfer fluid (oil) through the bellows allows the capacitor to operate at significantly higher currents and/or lower temperatures, and significantly extends the life of the device.

A variable vacuum capacitor is described in which oil inside the main bellows (21) is pumped through the bellows and through the oil circuit (8) of a heat exchanger by a pump (15). Water passes through coolant channels (6) of the heat exchanger, from inlet (7) to outlet (7′). The extendable capacitor drive shaft (14) is hollow and serves as a conduit, conveying the oil to the bottom of the (bellows 21), thereby ensuring a full circulation of the oil right through the bellows and then through the heat exchanger. Pump drive means (9) may be a gerotor hydraulic motor, coupled to a gerotor oil pump (15) via magnetic coupling (22). Pumping heat transfer fluid (oil) through the bellows allows the capacitor to operate at significantly higher currents and/or lower temperatures, and significantly extends the life of the device.

A variable vacuum capacitor is described in which oil inside the main bellows (21) is pumped through the bellows and through the oil circuit (8) of a heat exchanger by a pump (15). Water passes through coolant channels (6) of the heat exchanger, from inlet (7) to outlet (7). The extendable capacitor drive shaft (14) is hollow and serves as a conduit, conveying the oil to the bottom of the (bellows 21), thereby ensuring a full circulation of the oil right through the bellows and then through the heat exchanger. Pump drive means (9) may be a gerotor hydraulic motor, coupled to a gerotor oil pump (15) via magnetic coupling (22). Pumping heat transfer fluid (oil) through the bellows allows the capacitor to operate at significantly higher currents and/or lower temperatures, and significantly extends the life of the device.

A variable vacuum capacitor is described in which oil inside the main bellows (21) is pumped through the bellows and through the oil circuit (8) of a heat exchanger by a pump (15). Water passes through coolant channels (6) of the heat exchanger, from inlet (7) to outlet (7). The extendable capacitor drive shaft (14) is hollow and serves as a conduit, conveying the oil to the bottom of the (bellows 21), thereby ensuring a full circulation of the oil right through the bellows and then through the heat exchanger. Pump drive means (9) may be a gerotor hydraulic motor, coupled to a gerotor oil pump (15) via magnetic coupling (22). Pumping heat transfer fluid (oil) through the bellows allows the capacitor to operate at significantly higher currents and/or lower temperatures, and significantly extends the life of the device.

A variable capacitor device that includes a dielectric layer comprising a shape-memory polymer, a first metal plate and a second metal plate, wherein the dielectric layer is sandwiched between the first and the second metal plates. The shape-memory polymer has a first thickness at a first temperature under a first external compressive load, a second thickness at a second temperature under a second external compressive load, wherein the first thickness is greater than the second thickness, the second temperature is greater than the first temperature, and the second external compressive load is greater than the first external compressive load. The shape memory polymer having the second thickness is configured to convert to the shape-memory polymer having the first thickness when sequentially subjected to the first external compressive load and the second temperature.

A capacitor assembly includes a capacitor having ends. A terminal covers less than an area of one end. A wire bond has opposing ends with one end being coupled to the terminal and is configured to break connection with a circuit when an electrical current through the wire bond reaches a fusing current. An energy storage module includes at least two capacitor assemblies. The wire bond of one capacitor is electrically connected to the second terminal of an adjacent capacitor. An energy storage assembly includes two energy storage modules stacked one on top of the other. A pulse forming network includes conductors and at least two energy storage modules. A method of making a module includes charging each of the capacitors, removing each capacitor that fails, connecting one end of a wire bond to one terminal and connecting the other end to an adjacent capacitor or to a conductor.

A high density capacitor comprises a housing having a cavity, and a plurality of capacitors forming at least one capacitor bank disposed in the housing cavity. A native cooling fluid is disposed in the cavity, and a heat exchanger is coupled to the housing. A pump is configured to circulate the native cooling fluid from the cavity, through the heat exchanger, through the spacings along an outer surface of each of the capacitors to cool the capacitors using forced convection. The heat exchanger is configured to communicate a secondary fluid through the heat exchanger and draw heat from the native cooling fluid flowing through the heat exchanger. The heat exchanger may have a plenum having a plurality of openings configured to dispense the native cooling fluid from the heat exchanger proximate the at least one capacitor bank.