Low leakage current electrical isolation system

Claim 2

An isolated hospital electrical supply system with very low leakage current to electrical ground potential and low noise for transforming AC voltage from an electrically grounded source and providing ungrounded AC voltage so as to minimize the possibility of electrical shock of a patient who is in contact with said electrical ground of said grounded source and to minimize audible noise generation in the system comprising: at least a first pair of lines for providing low frequency alternating voltage from an electrical utility line, one of said lines being electrically connected to ground potential; an electrical outlet receptacle adapted for connection to electrical equipment; at least a second pair of lines connected in circuit with said electrical outlet receptacle for conducting alternating voltage to said outlet receptacle, neither one of said second pair of lines being connected to said ground potential; an isolation transformer located spaced from said outlet receptacle, said isolation transformer including: a core of magnetic material; a first coil of wire containing a first predetermined number of turns, Np, comprising a primary winding; a second separate coil of wire containing a second predetermined number of turns, Nsl, comprising a first secondary winding; a third separate coil of wire containing a third predetermined number of turns, Ns2, comprising a second secondary winding, said third coil of wire being substantially identical with said second coil of wire and said second and third predetermined number of turns of wire being the same; first and second nonmagnetic metal shields having a passage therethrough and a slot between said passage and an outer edge thereof; said first, second and third coil being electrically insulated from said core and mounted on said core side by side and closely adjacent one another with said second coil located adjacent one side of said first coil and with said third coil located adjacent the remaining side of said first coil; said second coil having the turns of wire therein wound in a clockwise direction as mounted on said core and said third coil having the turns of wire therein wound in a counterclockwise direction as mounted on said core; and wherein the ratio, Ns1/Np, is equal to a number less than 3 and at least 1, and wherein the ratio, Ns2/Np, is equal to a number less than 3 and at least 1; said first shield mounted on said core sandwiched between one side of said first coil and said second coil and said second shield mounted on said core sandwiched between the remaining side of said first coil and said third coil; means electrically connecting the sTart end of one of said secondary windings to the finish end of the other and the finish end of said one secondary winding to the start end of said other secondary winding to place said secondary windings in parallel; means connecting each of said shield members and said magnetic core electrically in common and to said ground potential; means connecting said first pair of lines in circuit with said primary winding for supplying alternating voltage thereto; and means connecting said second pair of lines in circuit across said secondary windings for coupling alternating voltages from said secondary windings to said outlet receptacle; whereby low frequency AC leakage current between said first and second pair of lines and between said second pair of lines and ground potential is minimized; a steel walled enclosure for housing electrical components, including said transformer, said enclosure being connected to electrical ground potential; said transformer being located in said enclosure; and means for extending said pair of lines through an enclosure wall into said enclosure.

Claim 3

An isolated hospital electrical supply system with very low leakage current to electrical ground potential and low noise for transforming AC voltage from a grounded source and providing ungrounded AC voltage so as to minimize the possibility of electrical shock of a patient who is in contact with said electrical ground of said grounded source and to minimize audible noise generation in the system comprising: at least a first pair of lines for providing low frequency alternating voltage from an electrical utility line, one of said lines being electrically connected to ground potential; first and second electrical outlet receptacle means adapted for connection to electrical equipment; at least a second pair of lines connected in circuit with said first electrical outlet receptacle means for conducting alternating voltage to said outlet receptacle means, neither one of said second pair of lines being connected to said ground potential; at least a third pair of lines connected in circuit with said second electrical outlet receptacle means for conducting alternating voltage to said outlet receptacle means, said second outlet receptacle means being isolated electrically from said first outlet receptacle means and neither one of said third pair of lines being connected to said ground potential; an isolation transformer located spaced from said outlet receptacle, said isolation transformer including: a core of magnetic material; a first coil of wire containing a first predetermined number of turns, Np, comprising a primary winding; a second separate coil of wire containing a second predetermined number of turns, Nsl, comprising a first secondary winding; a third separate coil of wire containing a third predetermined number of turns, Ns1, comprising a second secondary winding, said third coil of wire being substantially identical with said second coil of wire and said second and third predetermined number of turns of wire being the same; first and second nonmagnetic metal shields having a passage therethrough and a slot between said passage and an outer edge thereof; said first, second and third coils being electrically insulated from one another and said core and mounted on said core side by side and closely adjacent one another with said second coil located adjacent one side of said first coil and with said third coil located adjacent the remaining side of said first coil; said second coil having the turns of wire therein wound in a clockwise direction as mounted on said core and said third coil having the turns of wire therein wound in a counterclockwise direction as mounted on said core; and wherein the ratio Ns1/Np is equal to a number less than 3 and at least 1; said first shield mounted on said core sandwiched between one side of said first coil and saiD second coil and said second shield mounted on said core sandwiched between the remaining side of said first coil and said third coil; means connecting each of said shield members and said magnetic core electrically in common and to said ground potential; means connecting said first pair of lines in circuit with said primary winding for supplying alternating voltage thereto; and means connecting said second pair of lines in circuit with the said first secondary winding for coupling alternating voltage from said first secondary winding to said first outlet receptacle means; and means connecting said third pair of lines in circuit with said second secondary winding for coupling alternating voltage from said second secondary winding to said second outlet receptacle means; a steel walled enclosure for housing electrical components, including said transformer, said enclosure being connected to electrical ground potential; said transformer being located in said enclosure; and means for extending said pair of lines through an enclosure wall into said enclosure.

Claim 4

An isolated hospital electrical supply system with very low leakage current to electrical ground potential and low noise for transforming AC voltage from a grounded source and providing ungrounded AC voltage so as to minimize the possibility of electrical shock of a patient who is in contact with said electrical ground of said grounded source and to minimize audible noise generation in the system comprising: at least a first pair of lines for providing low frequency alternating voltage from an electrical utility line, one of said lines being electrically connected to ground potential; first and second electrical outlet receptacle means adapted for connection to electrical equipment; at least a second pair of lines connected in circuit with said first electrical outlet receptacle means for conducting alternating voltage to said outlet receptacle means, neither one of said second pair of lines being connected to said ground potential; at least a third pair of lines connected in circuit with said second electrical outlet receptacle means for conducting alternating voltage to said outlet receptacle means, said second outlet receptacle means being isolated electrically from said first outlet receptacle means and neither one of said third pair of lines being connected to said ground potential; an isolation transformer located spaced from said outlet receptacle, said isolation transformer including: a core of magnetic material; a first coil of wire containing a first predetermined number of turns, Np, comprising a primary winding; a second separate coil of wire containing a second predetermined number of turns, Nsl, comprising a first secondary winding; a third separate coil of wire containing a third predetermined number of turns, Ns1, comprising a second secondary winding, said third coil of wire being substantially identical with said second coil of wire and said second and third predetermined number of turns of wire being the same; first and second nonmagnetic metal shields having a passage therethrough and a slot between said passage and an outer edge thereof; said first, second and third coils being electrically insulated from one another and said core and mounted on said core side by side and closely adjacent one another with said second coil located adjacent one side of said first coil and with said third coil located adjacent the remaining side of said first coil; said second coil having the turns of wire therein wound in a clockwise direction as mounted on said core and said third coil having the turns of wire therein wound in a counterclockwise direction as mounted on said core; and wherein the ratio Ns1/Np is equal to a number less than 3 and at least 1; said first shield mounted on said core sandwiched between one side of said first coil and saiD second coil and said second shield mounted on said core sandwiched between the remaining side of said first coil and said third coil; means connecting each of said shield members and said magnetic core electrically in common and to said ground potential; means connecting said first pair of lines in circuit with said primary winding for supplying alternating voltage thereto; and means connecting said second pair of lines in circuit with the said first secondary winding for coupling alternating voltage from said first secondary winding to said first outlet receptacle means; and means connecting said third pair of lines in circuit with said second secondary winding for coupling alternating voltage from said second secondary winding to said second outlet receptacle means; a steel walled enclosure for housing electrical components, including said transformer, said enclosure being connected to electrical ground potential; said transformer being located in said enclosure; and means for extending said pair of lines through an enclosure wall into said enclosure.