Electromagnetic pulse isolation transformer

Claim 2

An isolation transformer for connection between a source of alternating current power and electronic components, the operation of which is adversely affected by voltage excursions caused by electromagnetic pulses, said transformer comprising: a core defining at least one window; a primary coil surrounding a first portion of said core and extending through a said at least one window in said core; a secondary coil, spaced from said primary coil, surrounding a second portion of said core and extending through a said at least one window in said core; a metallic isolation plate disposed between said coils; a metallic housing mounted on said plate and receiving said primary coil and the portion of said core on the primary coil side of said plate; and an electrically conductive coating disposed about said primary coil and insulated therefrom, said coating being electrically connected to said housing so that said housing, said plate and said coating form a Faraday cage, said plate extending beyond said housing and forming a mounting flange for said transformer.

Claim 3

An isolation transformer for connection between a source of alternating current power and electronic components, the operation of which components is adversely affected by voltage excursions occasioned by electromagnetic pulses, said transformer comprising: a ferromagnetic core including a first end, a second end and at least two legs extending intermediate said ends and defining therewith at least one window in said core; a primary coil surrounding a first portion of said core and extending through a said at least one window in said core; a secondary coil, spaced from said primary coil, surrounding a second portion of said core and extending through a said at least one window in said core; a metallic isolation shield disposed between said primary coil and said secondary coil, said shield having core apertures for receiving components of said core so that said shield passes through each window of said core; a first metallic housing mounted on said shield and having an opening for receiving said primary coil and the portion of said core on the primary coil side of said shield; and an electrically conductive first foil wrapped about and insulated from said primary coil and electrically connected to said housing so that said housing, said shield and said foil form a first Faraday cage, said primary coil having leads passing through said foil and outside said housing with said shield extending beyond said housing to form a mounting flange for said transformer.

Claim 4

An isolation transformer for connection between a source of alternating current power and electronic components, the operation of which components is adversely affected by voltage excursions occasioned by electromagnetic pulses, said transformer comprising: a ferromagnetic core including a first end, a second end and at least two legs extending intermediate said ends and defining therewith at least one window in said core; a primary coil surrounding a first portion of said core and extending through a said at least one window in said core; a secondary coil, spaced from said primary coil, surrounding a second portion of said core and extending through a said at least one window in said core; a metallic isolation shield disposed between said primary coil and said secondary coil, said shield having core apertures for receiving components of said core so that said shield passes through each window of said core; a first metallic housing mounted on said shield and having an opening for receiving said primary coil and the portion of said core on the primary coil side of said shield; and an electrically conductive first foil wrapped about and insulated from said primary coil and electrically connected to said housing so that said housing, said shield and said foil form a first Faraday cage, said primary coil having leads passing through said foil and outside said housing with said shield extending beyond said housing to form a mounting flange for said transformer.

Claim 5

A transformer as set forth in claim 2 further comprising a second metallic housing mounted on said shield and having an opening for receiving said secondary coil and the portion of said core on the secondary winding side of said shield.

Claim 6

A transformer as set forth in claim 3 further including an electrically conductive second foil wrapped about and insulated from said secondary coil and electrically connected to said second housing so that said second housing, said shield and said second foil form a second Faraday cage, said secondary coil having leads passing through said second foil and outside said second housing.

Claim 7

A transformer as set forth in claim 2 wherein said metallic housing has a second opening through which said first foil extends, said foil being bonded by electrically conductive means to material of said first metallic housing defining said second opening.

Claim 8

A transformer as set forth in claim 5 wherein said second opening extends adjacent to said isolation shield, said foil being bonded by electrically conductive means to said shield.

Claim 9

A transformer as set forth in claim 2 wherein said shield is a plate having a plurality of spaced mounting apertures disposed adjacent its periphery.

Claim 10

A transformer as set forth in claim 2 wherein there is a plurality of apertures and said shield has a slot extending between each pair of adjacent apertures to interrupt the electrically conductive paths about those core apertures formed by shield material defining those core apertures, thereby reducing eddy current losses.

Claim 11

A transformer as set forth in claim 8 wherein one leg of said core passes through a corresponding one of said core apertures, each leg being bonded to the shield material defining its corresponding core aperture by electrically conductive bonding means terminating short of the slot extending to that core aperture.

Claim 12

A transformer as set forth in claim 8 wherein said slot is bridged by a metallic arm connected to the shield on one side of said slot and spaced from the shield on the other side of the slot by an insulator, thereby reducing radiation leakage.

Claim 13

A transformer as set forth in claim 2 wherein said first foil has a first end and a second end, said foil being spirally wrapped about the wires of said primary coil, said foil forming at least two layers about the periphery of said primary coil with said layers being insulated from each other by a layer of insulation so that said foil does not make a closed electrically conductive path around the periphery of said primary coil.

Claim 14

A transformer as set forth in claim 11 further comprising a capacitor connected between said layers of said foil.

Claim 15

An isolation transformer system for connection between a source of alternating current power and electronic components, the operation of which components is adversely affected by voltage excursions caused by electromagnetic pulses, said system comprising an enclosure for said electronic components having a metallic wall with an opening therethrough, said system further including an isolation transformer comprising: a ferromagnetic core including a first end, a second end and at least two legs extending intermediate between said ends and defining therewith at least one window in said core; a primary coil surrounding a first portion of said core and extending through a said at least one window in said core; a secondary coil, spaced from said primary coil, surrounding a second portion of said core and extending through a said at least one window in said core; a metallic isolation shield disposed between said primary coil and said secondary coil, said shield having core apertures for receiving components of said core so that said shield passes through each window of said core; a first metallic housing mounted on said shield and having an opening receiving said primary coil and the portion of said core on the primary winding side of said shield; an electrically conductive first foil wrapped about said primary coil and insulated therefrom and electrically connected to said housing so that said housing, said shield and said foil form a Faraday cage, said primary coil having leads passing through said foil and outside said housing with said shield extending beyond said housing to form a mounting flange for said transformer, said flange being fastened to material defining the opening in said wall of said enclosure.

Claim 16

An isolation transformer system for connection between a source of alternating current power and electronic components, the operation of which components is adversely affected by voltage excursions caused by electromagnetic pulses, said system comprising an enclosure for said electronic components having a metallic wall with an opening therethrough, said system further including an isolation transformer comprising: a ferromagnetic core including a first end, a second end and at least two legs extending intermediate between said ends and defining therewith at least one window in said core; a primary coil surrounding a first portion of said core and extending through a said at least one window in said core; a secondary coil, spaced from said primary coil, surrounding a second portion of said core and extending through a said at least one window in said core; a metallic isolation shield disposed between said primary coil and said secondary coil, said shield having core apertures for receiving components of said core so that said shield passes through each window of said core; a first metallic housing mounted on said shield and having an opening receiving said primary coil and the portion of said core on the primary winding side of said shield; an electrically conductive first foil wrapped about said primary coil and insulated therefrom and electrically connected to said housing so that said housing, said shield and said foil form a Faraday cage, said primary coil having leads passing through said foil and outside said housing with said shield extending beyond said housing to form a mounting flange for said transformer, said flange being fastened to material defining the opening in said wall of said enclosure.

Claim 17

An isolation transformer for connection between a source of alternating current power and electronic components, the operation of which is adversely affected by voltage excursions caused by electromagnetic pulses, said transformer comprising: a ferromagnetic core defining at least one window; a primary coil surrounding a first portion of said core and extending through a said at least one window in said core; a secondary coil spaced from said primary coil, surrounding a second portion of said core and extending through a said at least one window in said core; a metallic wall, which forms a part of an enclosure for said electronic components, disposed between said primary coil and said secondary coil, said wall having core apertures for receiving components of said core so that said wall passes through each window of said core; a metallic housing mounted on said wall and receiving said primary coil and the portion of said core on the primary coil side of said wall; and an electrically conductive foil wrapped about and insulated from said primary coil and electrically connected to said housing so that said housing, said wall and said foil form a first Faraday cage, said wall forming an isolation shield for said transformer.

Claim 18

An isolation transformer for connection between a source of alternating current power and electronic components, the operation of which is adversely affected by voltage excursions caused by electromagnetic pulses, said transformer comprising: a ferromagnetic core defining at least one window; a primary coil surrounding a first portion of said core and extending through a said at least one window in said core; a secondary coil spaced from said primary coil, surrounding a second portion of said core and extending through a said at least one window in said core; a metallic wall, which forms a part of an enclosure for said electronic components, disposed between said primary coil and said secondary coil, said wall having core apertures for receiving components of said core so that said wall passes through each window of said core; a metallic housing mounted on said wall and receiving said primary coil and the portion of said core on the primary coil side of said wall; and an electrically conductive foil wrapped about and insulated from said primary coil and electrically connected to said housing so that said housing, said wall and said foil form a first Faraday cage, said wall forming an isolation shield for said transformer.