Load tap changer apparatus with magnetic transducer protective circuitry

Claim 2

A load tap changer system comprising: an electrical circuit including a winding having a plurality of taps, tap selector switching means having first and second contact arms selectively movable between a plurality of electrical contacts connected to taps on said winding, reactor means having first and second winding portions, bypass switching means having first, second and third terminals, actuable to connect the third terminal to either or both of the first and second terminals, said third terminal being connected in said electrical circuit, means serially connecting said first contact arm and the first winding portion of said reactor means to the first terminal of said bypass switching means, providing a first series branch, means serially connecting said second contact arm and the second winding portion of said reactor means to the second terminal of said bypass switching means, providing a second series branch, a load transfer switch connected between the first and second terminals of said bypass switching means, drive means for operating said bypass switching means, said transfer switch, and said tap selector switching means in a predetermined sequence, when it is desired to change the operating position of said tap selector switching means, magnetic transducer means disposed in the magnetic field produced by current flowing through said transfer switch, but spaced therefrom beyond the jump distance to ground for the voltage magnitude applied to said transfer switch, said magnetic transducer means providing an electrical signal only when current is flowing through said transfer switch, and protective means connected to said magnetic transducer means, said protective means being responsive to the electrical signal from said magnetic transducer means, preventing the operation of said tap selector switching means while current is flowing through said transfer switch.

Claim 3

The load tap changer system of claim 1 wherein the load transfer switch is a vacuum switch.

Claim 4

The load tap changer system of claim 1 wherein the protective means includes a cam operated switch actuated by the drive means prior to the operation of the tap selector switching means, to check for current flow through the transfer switch, said cam operated switch being connected to render the protective means operative to prevent the operation of the tap selector switching means while current is flowing through the transfer switch.

Claim 5

The load tap changer system of claim 1 wherein the drive means is mechanically linked to the bypass switching means, the transfer switch, and the tap selector switching means, such that when a tap change is desired the drive means sequentially actuates the bypass switching means to open one of the series branches, opens the transfer switch, moves the contact arm of the tap selector switching means associated with the open series branch, to a different electrical contact, closes the vacuum switch, and actuates the bypass switching means to close the open series branch.

Claim 6

A load tap changer system comprising: an electrical circuit including a winding having a plurality of taps, tap selector switch means having first and second contact arms selectively movable between a plurality of electrical contacts connected to taps on said winding, reactor means having first and second winding portions, bypass switching means having first, second and third terminals, actuable to connect the third terminal to either or both of the first and second terminals, said third terminal being connected in said electrical circuit, means serially connecting said first contact arm and the first winding portion of said reactor means to the first terminal of said bypass switching means, providing a first series branch, means serially connecting said second contact arm and the second winding portion of said reactor means to the second terminal of said bypass switching means, providing a second series branch, a load transfer switch connected between the first and second terminals of said bypass switching means, drive means for operating said bypass switching means, said transfer switch, and said tap selector switching means in a predetermined sequence when it is desired to change the operating position of said tap selector switching means, first and second magnetic transducer means disposed in the magnetic field produced by current flowing through said first and second series branches, respectively, but spaced from said first and second series branches beyond the voltage jump distance to ground, said first and second magnetic transducer means providing electrical output signals in response to current flow through said first and second series branches, respectively, and protective means connected to said first and second magnetic transducer means, said protective means being responsive to the electrical signals from said first and second magnetic transducer means, preventing the operation of said tap selector switching means when current is flowing through the series branch associated with the contact arm of the tap selector switching means which is to be actuated.

Claim 7

A load tap changer system comprising: an electrical circuit including a winding having a plurality of taps, tap selector switch means having first and second contact arms selectively movable between a plurality of electrical contacts connected to taps on said winding, reactor means having first and second winding portions, bypass switching means having first, second and third terminals, actuable to connect the third terminal to either or both of the first and second terminals, said third terminal being connected in said electrical circuit, means serially connecting said first contact arm and the first winding portion of said reactor means to the first terminal of said bypass switching means, providing a first series branch, means serially connecting said second contact arm and the second winding portion of said reactor means to the second terminal of said bypass switching means, providing a second series branch, a load transfer switch connected between the first and second terminals of said bypass switching means, drive means for operating said bypass switching means, said transfer switch, and said tap selector switching means in a predetermined sequence when it is desired to change the operating position of said tap selector switching means, first and second magnetic transducer means disposed in the magnetic field produced by current flowing through said first and second series branches, respectively, but spaced from said first and second series branches beyond the voltage jump distance to ground, said first and second magnetic transducer means providing electrical output signals in response to current flow through said first and second series branches, respectively, and protective means connected to said first and second magnetic transducer means, said protective means being responsive to the electrical signals from said first and second magnetic transducer means, preventing the operation of said tap selector switching means when current is flowing through the series branch associated with the contact arm of the tap selector switching means which is to be actuated.

Claim 8

The load tap changer system of claim 5 wherein the transfer switch is a vacuum switch.

Claim 9

The bad tap changer system of claim 5 wherein the protective means includes first and second cam operated switches, operated by the drive means prior to the movement of the first and second contact arms, respectively, of the tap selector switching means, to check for current flow through the first and second series branches, respectively, and render the protective means operative to prevent operation of a contact arm when current is flowing therethrough.

Claim 10

The load tap changer system of claim 5 wherein the drive means is mechanically linked to the bypass switching means, the tRansfer switch, and the tap selector switching means such that when a tap change is desired the drive means sequentially actuates the bypass switching means to open one of the series branches, opens the transfer switch, moves the contact arm of the tap selector switching means associated with the open series branch to a different electrical contact, closes the vacuum switch, and actuates the bypass switching means to close the open series branch.