Overcurrent protection for solid-state voltage regulator

Claim 2

In a solid-state voltage regulator connected between input and output terminals and including at least one voltage-injecting transformer winding stage having a shunt-exciting winding and an inductively coupled secondary winding, a plurality of bidirectional conducting solid-state switching means each connected to spaced taps on said secondary winding, and a synchronous gating circuit for controlling said solid-state switching means to inject selected voltage increments in series with the input voltage to regulate the output voltage, wherein at least some of said solid-state switching means are low-currentrating devices that are damaged by conducting overcurrents for a time period longer than a relatively short critical interval, the improvement which comprises overcurrent sensing means, and fast-acting overcurrent protection means responsive to said overcurrent sensing means for temporarily diverting the overcurrent from said low-current-rating devices within an interval shorter than the critical interval during which overcurrents can be conducted without damage, wherein one of said solid-state switching means comprises at least one high-current-rating device capable of conducting the overcurrent for a substantial period of time, and said overcurrent protection means includes means for modifying the action of said synchronous gating circuit to synchronously render conductive said high-current-rating device to conduct the overcurrent while simultaneously inhibiting the gating of said low-current-rating devices.

Claim 3

A circuit according to claim 1 wherein said high-current-rating device that conducts the overcurrent is connected to the tap on said secondary winding that results in the lowest output voltage.

Claim 4

In a solid-state voltage regulator connected between input and output terminals and including at least one voltage-injecting transformer winding stage having a shunt-exciting winding and an inductively coupled secondary winding, a plurality of bidirectional conducting solid-state switching means each connected to spaced taps on said secondary winding, and a synchronous gating circuit for controlling said solid-state switching means to inject selected voltage increments in series with the input voltage to regulate the output voltage, wherein at least some of said solid-state switching means are low-current-rating devices that are damaged by conducting overcurrents for a time period longer than a relatively short critical interval, the improvement which comprises overcurrent sensing means, and fast-acting overcurrent protection means responsive to said overcurrent-sensing means for temporarily diverting the overcurrent from said low-current-rating devices within an interval shorter than the critical interval during which overcurrents can be conducted without damage, wherein all of said solid-state switching means comprise low-current-rating devices, and said overcurrent protection means includes means for synchronously rendering conductive said low-current-rating devices in sequence to transfer the overcurrent from one to the other after an interval of conduction shorter than the critical interval to take advantage of the short time current overcapacity of the devices.

Claim 5

In a solid-state voltage regulator connected between input and output terminals and including at least one voltage-injecting transformer winding stage having a shunt-exciting winding and an inductively coupled secondary winding, a plurality of bidirectional conducting solid-state switching means each connected to spaced taps on said secondary winding, and a synchronous gating circuit for controlling said solid-state switching means to inject selected voltage increments in series with the input voltage to regulate the output voltage, wherein at least some of said solid-state switching means are low-current-rating devices that are damaged by conducting overcurrents for a time period longer than a relatively short critical interval, the improvement which comprises overcurrent sensing means, and fast-acting overcurrent protection means responsive to said overcurrent-sensing means for temporarily diverting the overcurrent from said low-current-rating devices within an interval shorter than the critical interval during which overcurrents can be conducted without damage, wherein all of said solid-state switching means comprise low-current-rating devices, and said overcurrent protection means includes means for synchronously rendering conductive said low-current-rating devices in sequence to transfer the overcurrent from one to the other after an interval of conduction shorter than the critical interval to take advantage of the short time current overcapacity of the devices.

Claim 6

In a solid-state voltage regulator connected between input and output terminals and including at least one voltage-injecting transformer winding stage having a shunt-exciting winding and an inductively coupled secondary winding, a plurality of bidirectional-conducting solid-state switching means each connected to spaced taps on said secondary winding, and a synchronous gating circuit for controlling said solid-state switching means inject selected voltage increments in series with input voltage to regulate the output voltage, wherein at least some of said solid-state switching means are low-current-rating devices that are damaged by conducting overcurrents for a time period longer than a relatively short critical interval, the improvement which comprises overcurrent-sensing means, and fast-acting overcurrent protection means responsive to said overcurrent sensing means for temporarily diverting the overcurrent from said low-current-rating devices within an interval shorter than the critical interval during which overcurrents can be conducted without damage, wherein all of said solid-atate switching means comprise low-current-rating devices, and said overcurrent protection means includes means for modifying the action of said synchronous gating circuit to synchronously render conductive said low-current-rating devices in a continuing sequence to transfer the overcurrent from one to the other after an interval of conduction shorter than the critical interval to take advantage of the short time current overcapacity of the devices.

Claim 7

In a solid-state voltage regulator connected between input and output terminals and including at least one voltage-injecting transformer winding stage having a shunt-exciting winding and an inductively coupled secondary winding, a plurality of bidirectional-conducting solid-state switching means each connected to spaced taps on said secondary winding, and a synchronous gating circuit for controlling said solid-state switching means inject selected voltage increments in series with input voltage to regulate the output voltage, wherein at least some of said solid-state switching means are low-current-rating devices that are damaged by conducting overcurrents for a time period longer than a relatively short critical interval, the improvement which comprises overcurrent-sensing means, and fast-acting overcurrent protection means responsive to said overcurrent sensing means for temporarily diverting the overcurrent from said low-current-rating devices within an interval shorter than the critical interval during which overcurrents can be conducted without damage, wherein all of said solid-atate switching means comprise low-current-rating devices, and said overcurrent protection means includes means for modifying the action of said synchronous gating circuit to synchronously render conductive said low-current-rating devices in a continuing sequence to transfer the overcurrent from one to the other after an interval of conduction shorter than the critical interval to take advantage of the short time current overcapacity of the devices.

Claim 8

In a solid-state voltage regulator connected between input and output terminals and including at least one voltage-injecting transformer winding stage having a shunt-exciting winding and an inductively coupled secondary winding, a plurality of bidirectional-conducting solid-state switching means each connected to spaced taps on said secondary winding, and a synchronous gating circuit for controlling said solid-state switching means to inject selected voltage increments in series with the input voltage to regulate the output voltage, wherein all of said solid-state switching means comprise low-current-rating devices that are damaged by conducting overcurrents of a predetermined magnitude for longer than a relatively short critical interval, the improvement which comprises overcurrent-sensing means, and fast-acting overcurrent protection means comprising a protective switch effectively connected in parallel circuit relationship with all of said solid-state switching means to divert the overcurrent from said low-current-rating devices to a low impedance path within the critical time interval, and an actuating circuit responsive to said overcurrent-sensing means for rendering conductive said protective switch upon the occurrence of an overcurrent, wherein said protective switch is an electromechanical contactor actuated by an associated coil, and said overcurrent-sensing means and actuating circuit includes an electronic circuit having a precharged capacitor thAt is discharged through the coil to close said contactor rapidly after the sensing of an overcurrent.

Claim 9

In a solid-state voltage regulator connected between input and output terminals and including at least one voltage-injecting transformer winding stage having a shunt-exciting winding and an inductively coupled secondary winding, a plurality of bidirectional-conducting solid-state switching means each connected to spaced taps on said secondary winding, and a synchronous gating circuit for controlling said solid-state switching means to inject selected voltage increments in series with the input voltage to regulate the output voltage, wherein all of said solid-state switching means comprise low-current-rating devices that are damaged by conducting overcurrents of a predetermined magnitude for longer than a relatively short critical interval, the improvement which comprises overcurrent-sensing means, and fast-acting overcurrent protection means comprising a protective switch effectively connected in parallel circuit relationship with all of said solid-state switching means to divert the overcurrent from said low-current-rating devices to a low impedance path within the critical time interval, and an actuating circuit responsive to said overcurrent-sensing means for rendering conductive said protective switch upon the occurrence of an overcurrent, wherein said protective switch is an electromechanical contactor actuated by an associated coil, and said overcurrent-sensing means and actuating circuit includes an electronic circuit having a precharged capacitor thAt is discharged through the coil to close said contactor rapidly after the sensing of an overcurrent.

Claim 10

A circuit according to claim 5 wherein one of said taps on said secondary winding is a neutral tap, and said protective switch is connected directly to said neutral tap and to a common connection between all of said solid-state switching means, to prevent circulating current through the closed protective switch.

Claim 11

In a solid-state voltage regulator connected between input and output terminals and including at least one voltage-injecting transformer winding stage having a shunt-exciting winding and an inductively coupled secondary winding, a plurality of bidirectional-conducting solid-state switching means each connected to spaced taps on said secondary winding, and a synchronous gating circuit for controlling said solid-state switching means to inject selected voltage increments in series with the input voltage to regulate the output voltage, wherein all of said solid-state switching means comprise low-current-rating devices that are damaged by conducting overcurrents of a predetermined magnitude for longer than a relatively short critical interval, the improvement which comprises overcurrent-sensing means, and fast-acting overcurrent protection means comprising a protective switch effectively connected in parallel circuit relationship will all of said solid-state switching means to divert the overcurrent from said low-current-rating devices to a low impedance path within the critical time interval, and an actuating circuit responsive to said overcurrent-sensing means for rendering conductive said protective switch upon the occurrence of an overcurrent, further including means for additionally rendering conductive said protective switch during the switching intervals of said solid-state switching means, whereby said protective switch has a dual function.

Claim 12

In a solid-state voltage regulator connected between input and output terminals and including at least one voltage-injecting transformer winding stage having a shunt-exciting winding and an inductively coupled secondary winding, a plurality of bidirectional-conducting solid-state switching means each connected to spaced taps on said secondary winding, and a synchronous gating circuit for controlling said solid-state switching means to inject selected voltage increments in series with the input voltage to regulate the output voltage, wherein all of said solid-state switching means comprise low-current-rating devices that are damaged by conducting overcurrents of a predetermined magnitude for longer than a relatively short critical interval, the improvement which comprises overcurrent-sensing means, and fast-acting overcurrent protection means comprising a protective switch effectively connected in parallel circuit relationship will all of said solid-state switching means to divert the overcurrent from said low-current-rating devices to a low impedance path within the critical time interval, and an actuating circuit responsive to said overcurrent-sensing means for rendering conductive said protective switch upon the occurrence of an overcurrent, further including means for additionally rendering conductive said protective switch during the switching intervals of said solid-state switching means, whereby said protective switch has a dual function.

Claim 13

In a solid-state voltage regulator connected between input and output terminals and including at least one voltage-injecting transformer winding stage having a shunt-exciting winding and an inductively coupled secondary winding with three spaced taps, bidirectional-conducting solid-state switching means connected to each of said taps to produce a high, medium, and low stage output voltage, and a synchronous gating circuit for controlling said solid-state switching means to inject a selected voltage increment in series with the input voltage to regulate the output voltage, wherein all of said solid-state switching means are low-current-rating devices that are damaged by conducting overcurrents for a time period longer than a relatively short critical interval, the improvement which comprises overcurrent-sensing means, and fast-acting overcurrent-sensing means, and operative during a portion of the interval before the opening of a conventional slow-acting circuit breaker connected in series with an input terminal, for switching the overcurrent from each low-current-rating device before damage occurs, wherein said overcurrent protection means includes means for continuously rendering conductive said low-current-rating devices in the sequence to produce high, medium, and low stage output voltages, each device conducting at any one time for an interval shorter than the critical interval during which the device safely passes overcurrents.

Claim 14

In a solid-state voltage regulator connected between input and output terminals and including at least one voltage-injecting transformer winding stage having a shunt-exciting winding and an inductively coupled secondary winding with three spaced taps, bidirectional-conducting solid-state switching means connected to each of said taps to produce a high, medium, and low stage output voltage, and a synchronous gating circuit for controlling said solid-state switching means to inject a selected voltage increment in series with the input voltage to regulate the output voltage, wherein all of said solid-state switching means are low-current-rating devices that are damaged by conducting overcurrents for a time period longer than a relatively short critical interval, the improvement which comprises overcurrent-sensing means, and fast-acting overcurrent-sensing means, and operative during a portion of the interval before the opening of a conventional slow-acting circuit breaker connected in series with an input terminal, for switching the overcurrent from each low-current-rating device before damage occurs, wherein said overcurrent protection means includes means for continuously rendering conductive said low-current-rating devices in the sequence to produce high, medium, and low stage output voltages, each device conducting at any one time for an interval shorter than the critical interval during which the device safely passes overcurrents.

Claim 15

In a solid-state voltage regulator connected between input and output terminals and including at least one voltage-injecting transformer winding stage having a shunt-exciting winding and an inductively coupled secondary winding with three spaced taps, bidirectional-conducting solid-state switching means connected to each of said taps to produce a high, medium, and low stage output voltage, and a synchronous gating circuit for controlling said solid-state switching means to inject a selected voltage increment in series with the input voltage to regulate the output voltage, wherein all of said solid-state switching means are low-current-raTing devices that are damaged by conducting overcurrents for a time period longer than a relatively short critical interval, the improvement which comprises overcurrent-sensing means, and fast-acting overcurrent protection means responsive to said overcurrent-sensing means, and operative during a portion of the interval before the opening of a conventional slow-acting circuit breaker connected in series with an input terminal, for switching the overcurrent from each low-current-rating device before damage occurs, wherein said overcurrent protection means comprises a protective switch connected in parallel circuit relationship will all of said low-current-rating devices, and means for rendering conductive said protective switch upon the sensing of an overcurrent, and wherein there are a plurality of voltage injection transformer winding stages each producing a plurality of selected voltage injection increments, and means for synchronously rendering conductive said protective switch to produce a zero voltage injection increment, whereby the protective switch has a dual function.

Claim 16

In a solid-state voltage regulator connected between input and output terminals and including at least one voltage-injecting transformer winding stage having a shunt-exciting winding and an inductively coupled secondary winding with three spaced taps, bidirectional-conducting solid-state switching means connected to each of said taps to produce a high, medium, and low stage output voltage, and a synchronous gating circuit for controlling said solid-state switching means to inject a selected voltage increment in series with the input voltage to regulate the output voltage, wherein all of said solid-state switching means are low-current-raTing devices that are damaged by conducting overcurrents for a time period longer than a relatively short critical interval, the improvement which comprises overcurrent-sensing means, and fast-acting overcurrent protection means responsive to said overcurrent-sensing means, and operative during a portion of the interval before the opening of a conventional slow-acting circuit breaker connected in series with an input terminal, for switching the overcurrent from each low-current-rating device before damage occurs, wherein said overcurrent protection means comprises a protective switch connected in parallel circuit relationship will all of said low-current-rating devices, and means for rendering conductive said protective switch upon the sensing of an overcurrent, and wherein there are a plurality of voltage injection transformer winding stages each producing a plurality of selected voltage injection increments, and means for synchronously rendering conductive said protective switch to produce a zero voltage injection increment, whereby the protective switch has a dual function.