Hvdc matrix design

Claim 2

In combination with a solid-state switching circuit that includes a first saturable core inductor in series with a series of thyristor sections each of which has at least one semiconductor controlled rectifier arranged to conduct electric current in a given direction through said circuit when triggered, said switching circuit being adapted to be connected to an AC electric power system and the controlled rectifiers of all of said sections being adapted to be cyclically triggered by associated control means, the improvement comprising: a. means for effectively shunting said first saturable core inductor with a resistance-inductance circuit having a pRedetermined total resistance and having a second saturable core inductor so constructed that after said controlled rectifiers are triggered it begins to saturate before said first saturable core inductor begins to saturate; and b. means operative after the magnitude of current flowing through said shunting means attains a peak for providing a relatively low impedance path across part of said resistanceinductance circuit, said part including said second inductor and a predetermined portion of said total resistance, whereupon i. electric energy stored in said second inductor is dissipated in said portion of said resistance, and ii. said first saturable core reactor is effectively shunted by only the remaining resistance.

Claim 3

The improvement as specified in claim 1 wherein the AC system has stray capacitance and total resistance of said resistance-inductance circuit has an underdamping ohmic value and wherein said remaining resistance has an overdamping ohmic value.

Claim 4

The improvement as specified in claim 2 wherein said second saturable core inductor begins to saturate before the magnitude of the current flowing through said shunting means attains a peak.

Claim 5

An improved electric current-switching circuit including, in series, a main saturable core inductor and at least one thyristor section comprising a controlled rectifier that will permit current to pass through said circuit in a given direction when triggered from a relatively high resistance nonconducting state to a low-resistance conducting state, wherein the improvement comprises shunting the main inductor with a parallel circuit including: a. a subcombination comprising a first resistor and an auxiliary saturable core inductor connected in series with each other, said auxiliary saturable core inductor being so constructed that it begins to saturate before said main saturable core inductor begins to saturate; b. switch means connected in parallel with said subcombination; c. at least one other resistor; d. means for connecting across said main inductor, said other resistor in series with the parallel combination of said switch means and said subcombination; e. said switch means being rendered conductive in response to a decrease in current flowing through said subcombination.

Claim 6

An improved electric current-switching circuit including, in series, a main saturable core inductor and at least one thyristor section comprising a controlled rectifier that will permit current to pass through said circuit in a given direction when triggered from a relatively high resistance nonconducting state to a low-resistance conducting state, wherein the improvement comprises shunting the main inductor with a parallel circuit including: a. a subcombination comprising a first resistor and an auxiliary saturable core inductor connected in series with each other, said auxiliary saturable core inductor being so constructed that it begins to saturate before said main saturable core inductor begins to saturate; b. switch means connected in parallel with said subcombination; c. at least one other resistor; d. means for connecting across said main inductor, said other resistor in series with the parallel combination of said switch means and said subcombination; e. said switch means being rendered conductive in response to a decrease in current flowing through said subcombination.

Claim 7

A switching circuit as specified in claim 4 wherein said switching means comprises rectifying means poled in opposition to said controlled rectifier and wherein said auxiliary inductor begins to saturate before said rectifying means is rendered conductive.

Claim 8

A commutation transient suppressing circuit connected in shunt across a main saturable core inductor which inductor is in series with a series of cyclically conducting thyristor sections in a power circuit having a predetermined stray capacitance comprising: a. a resistance in series with an auxiliary saturable core inductor, said auxiliary inductor being so constructed as to begin saturation before said main saturable core inductor begins to saturate; b. switch means in shunt across said auxiliary inductor and a portion of said resistance, said switch means being rendered conductive in response to a decrease in current flowing through said resistance and said auxiliary inductor whereupon i. electric energy stored in said auxiliary inductor is dissipated in said portion of said resistance, and ii. said main inductor is effectively shunted by only the remaining resistance.

Claim 9

A commutation transient suppressing circuit connected in shunt across a main saturable core inductor which inductor is in series with a series of cyclically conducting thyristor sections in a power circuit having a predetermined stray capacitance comprising: a. a resistance in series with an auxiliary saturable core inductor, said auxiliary inductor being so constructed as to begin saturation before said main saturable core inductor begins to saturate; b. switch means in shunt across said auxiliary inductor and a portion of said resistance, said switch means being rendered conductive in response to a decrease in current flowing through said resistance and said auxiliary inductor whereupon i. electric energy stored in said auxiliary inductor is dissipated in said portion of said resistance, and ii. said main inductor is effectively shunted by only the remaining resistance.

Claim 10

A commutation transient suppressing circuit as specified in claim 6 wherein the first-mentioned resistance has an underdamping ohmic value and wherein said remaining resistance has an overdamping ohmic value.

Claim 11

A commutation transient suppressing circuit as specified in claim 7 wherein said auxiliary inductor begins to saturate prior to said switch means being rendered conductive.

Claim 12

An electric current-switching circuit comprising: a. first and second thyristor sections each having an anode and a cathode; b. first means for connecting the cathode of said first thyristor section to the anode of said second thyristor section; c. first and second voltage-dividing bypass subcircuits respectively comprising a capacitance element in series with a resistance element, each of said subcircuits having first and second ends; d. a first saturable core inductor connected between the first end of said first subcircuit and the anode of said first thyristor section; e. a second saturable core inductor connected between the first end of said second subcircuit and the cathode of said second thyristor section; and f. second means for connecting the second ends of said first and second subcircuits to each other and to said first means.

Claim 13

An electric current-switching circuit comprising: a. first and second thyristor sections each having an anode and a cathode; b. first means for connecting the cathode of said first thyristor section to the anode of said second thyristor section; c. first and second voltage-dividing bypass subcircuits respectively comprising a capacitance element in series with a resistance element, each of said subcircuits having first and second ends; d. a first saturable core inductor connected between the first end of said first subcircuit and the anode of said first thyristor section; e. a second saturable core inductor connected between the first end of said second subcircuit and the cathode of said second thyristor section; and f. second means for connecting the second ends of said first and second subcircuits to each other and to said first means.

Claim 14

The electric current-switching circuit as specified in claim 9 wherein said circuit additionally comprises: g. third thyristor and fourth thyristor sections each having an anode and a cathode; h. third means for connecting the cathode of said third thyristor section to the anode of said first thyristor section; i. fourth means for connecting the anode of said fourth thyristor section to the cathode of said second thyristor section; j. a third voltage-dividing bypass subcircuit comprising a capacitance element in series with a resistance element, said third subcircuit being connected between the anode of said third thyristor section and the first end of said first subcircuit; k. a fourth voltage-dividing bypass subcircuit comprising a capacitance element in series with a resistance element, said fourth subcircuit being connected between the cathode of said fourth thyristor section and the first end of said second subcircuit,

Claim 15

The electric current-switching circuit as specified in claim 10 wherein additional capacitance means is connected across a predetermined portion of the resistance in said first subcircuit and a corresponding portion of the resistance in said second subcircuit.

Claim 16

An electric current-switching circuit comprising: a. first and second thyristor sections each comprising at least one controlled rectifier having an anode and a cathode between which electric current is conducted when the rectifier is triggered; b. a main saturable core inductor connected between the cathode of said first thyristor section and the anode of said second thyristor section; c. first and second voltage-dividing bypass subcircuits respectively comprising a capacitance element in series with a resistance element, each of said subcircuits having first and second ends; d. a first inductance element connected between the first end of said first subcircuit and the anode of said first thyristor section; e. a second inductance element connected between the first end of said second subcircuit and the cathode of said second thyristor section; f. means for effectively shunting said main saturable core inductor with a resistance-inductance circuit comprising an auxiliary inductor and a predetermined total resistance; g. means operative after the magnitude of current flowing through said resistance-inductance circuit attains a peak for providing a relatively low impedance path across part of said resistance-inductance circuit, said part including said auxiliary inductor and a predetermined portion of the resistance of said circuit; and h. means for connecting said last mentioned means to the second ends of both of said subcircuits.

Claim 17

An electric current-switching circuit comprising: a. first and second thyristor sections each comprising at least one controlled rectifier having an anode and a cathode between which electric current is conducted when the rectifier is triggered; b. a main saturable core inductor connected between the cathode of said first thyristor section and the anode of said second thyristor section; c. first and second voltage-dividing bypass subcircuits respectively comprising a capacitance element in series with a resistance element, each of said subcircuits having first and second ends; d. a first inductance element connected between the first end of said first subcircuit and the anode of said first thyristor section; e. a second inductance element connected between the first end of said second subcircuit and the cathode of said second thyristor section; f. means for effectively shunting said main saturable core inductor with a resistance-inductance circuit comprising an auxiliary inductor and a predetermined total resistance; g. means operative after the magnitude of current flowing through said resistance-inductance circuit attains a peak for providing a relatively low impedance path across part of said resistance-inductance circuit, said part including said auxiliary inductor and a predetermined portion of the resistance of said circuit; and h. means for connecting said last mentioned means to the second ends of both of said subcircuits.

Claim 18

An electric current-switching circuit as specified in claim 12 wherein said auxiliary inductor has a saturable core and is so constructed as to begin saturating before said main saturable core inductor begins to saturate.

Claim 19

The electric current-switching circuit as specified in claim 12 wherein additional capacitance means is connected across a predetermined portion of the resistance in said first subcircuit and a corresponding portion of the resistance in said second subcircuit.

Claim 20

An electric current-switching circuit as specified in claim 14 wherein said auXiliary inductor has a saturable core and is so constructed as to begin saturating before said main saturable core inductor begins to saturate.

Claim 21

An electric current-switching circuit comprising: a. a pair of adjoining thyristor sections connected at a first point; b. a pair of voltage-dividing resistance-capacitance subcircuits connected across said thyristor sections, respectively; c. a current-limiting inductance element connected between said first point and the common junction of said subcircuits; and d. means responsive to the detection of a forward steep front surge of abnormally high forward voltage on said switching circuit for causing a predetermined one of said thyristor sections to turn on before the other, whereby said inductance element can safely limit current in the first-on section and at the same time effect dv/dt turn on of said other section.

Claim 22

An electric current-switching circuit comprising: a. a pair of adjoining thyristor sections connected at a first point; b. a pair of voltage-dividing resistance-capacitance subcircuits connected across said thyristor sections, respectively; c. a current-limiting inductance element connected between said first point and the common junction of said subcircuits; and d. means responsive to the detection of a forward steep front surge of abnormally high forward voltage on said switching circuit for causing a predetermined one of said thyristor sections to turn on before the other, whereby said inductance element can safely limit current in the first-on section and at the same time effect dv/dt turn on of said other section.

Claim 23

An electric current-switching circuit as specified in claim 16 wherein said last-mentioned means comprises additional capacitance means connected across a predetermined portion of the resistance in the subcircuit that is associated with said other thyristor section.

Claim 24

The electric current-switching circuit as specified in claim 16 wherein commutation transient suppression means is connected in series with said thyristor sections.

Claim 25

In combination with a solid-state switching circuit including at least two pairs of serially related thyristor sections each of which is shunted by a series resistance-capacitance voltage dividing bypass subcircuit the improvement which comprises additional capacitance means shunting a portion of the resistance in a predetermined one of said bypass sub circuits and a corresponding portion of the resistance in an adjoining one of said bypass subcircuits.

Claim 26

In combination with a solid-state switching circuit including at least two pairs of serially related thyristor sections each of which is shunted by a series resistance-capacitance voltage dividing bypass subcircuit the improvement which comprises additional capacitance means shunting a portion of the resistance in a predetermined one of said bypass sub circuits and a corresponding portion of the resistance in an adjoining one of said bypass subcircuits.

Claim 27

The improvement as specified in claim 19 wherein said additional capacitance means does not shunt any portion of the capacitance of either bypass subcircuit.