AC--AC Converter device

Claim 2

An AC--AC converter device comprising: a converter circuit for connection to a source of polyphase alternating current capable of instantaneously varying an output voltage to a positive voltage, a negative voltage or zero; and a coupled reactor commutating inverter circuit cascade-connected to said converter circuit, said inverter circuit consisting of only coupled reactors and a plurality of thyristors which and rendered conductive in a predetermined sequence, whereby said output voltage of said converter circuit is rendered positive, negative or zero instantaneously as necessary to effect commutation and current control in said inverter circuit.

Claim 3

An AC--AC converter device comprising: a pair of converter circuits, each capable of instantaneously varying an output voltage to a positive voltage, a negative voltage or zero; a pair of coupled reactor commutating inverter circuits cascade-connected to a corresponding one of said pair of converter circuits for parallel-connection to an AC motor as a load, each of said inverter circuits including first and second magnetically coupled reactors having first and second terminals, said first terminals connected to respective input terminals of said inverter circuit, said first reactors of each of said inverter circuits magnetically coupled together and said second reactors of each of said inverter circuits magnetically coupled together, said inverter circuits further including a plurality of separation thryistors connected as a unit between said second terminals of said first and second reactors, each series connection point of said separation thyristor units for connection to star-connected armature coils of the AC motor as a load, said separation thyristors rendered conductive and controlled in accordance with a predetermined sequence, whereby said output voltage of each of said pair of converter circuits is rendered positive, negative or zero as necessary to effect commutation and current control in said corresponding inverter circuit.

Claim 4

An AC--AC converter device comprising: a pair of converter circuits, each capable of instantaneously varying an output voltage to a positive voltage, a negative voltage or zero; a pair of coupled reactor commutating inverter circuits cascade-connected to a corresponding one of said pair of converter circuits for parallel-connection to an AC motor as a load, each of said inverter circuits including first and second magnetically coupled reactors having first and second terminals, said first terminals connected to respective input terminals of said inverter circuit, said first reactors of each of said inverter circuits magnetically coupled together and said second reactors of each of said inverter circuits magnetically coupled together, said inverter circuits further including a plurality of separation thryistors connected as a unit between said second terminals of said first and second reactors, each series connection point of said separation thyristor units for connection to star-connected armature coils of the AC motor as a load, said separation thyristors rendered conductive and controlled in accordance with a predetermined sequence, whereby said output voltage of each of said pair of converter circuits is rendered positive, negative or zero as necessary to effect commutation and current control in said corresponding inverter circuit.

Claim 5

An AC--AC converter device comprising: a converter circuit for connection to a source of polyphase alternating current capable of instantaneously varying an output voltage to a positive voltage, a negative voltage or zero, and converter circuit comprising a rectifier circuit having a polyphase thyristor bridge for connection to the source of polyphase alternating current; a chopper unit connected to the DC output side of said rectifier circuit having two chopper elements and a current blocking diode connected across said rectifier circuit; and a coupled reactor commutating inverter circuit cascade-connected to said converter circuit, said inverter circuit comprising a pair of magnetically coupled reactors each having first and second terminals, said first terminals connected to respective terminals of the input of said magnetically coupled reactors; means for connection of each series connection point of said separation thyristor unit to respective star-connected armature coils of an AC motor as a load; circulation thyristors connected in series between the respective input terminals of said inverter circuit; and means to connect the series connection point of the circulation thyristors to the neutral point of the star-connected armature coils of the AC motor; whereby said separation thyristors and said circulation thyristors of said inverter circuit are rendered conductive and controlled in accordance with a predetermined sequence, respectively, and said polyphase thyristor bridge rectifier circuit and said chopper elements are rendered conductive or nonconductive as necessary to render the output voltage of said converter circuit positive, negative or zero to effect commutation and current control.

Claim 6

An AC--AC converter device comprising: a converter circuit for connection to a source of polyphase alternating current capable of instantaneously varying an output voltage to a positive voltage, a negative voltage or zero, and converter circuit comprising a rectifier circuit having a polyphase thyristor bridge for connection to the source of polyphase alternating current; a chopper unit connected to the DC output side of said rectifier circuit having two chopper elements and a current blocking diode connected across said rectifier circuit; and a coupled reactor commutating inverter circuit cascade-connected to said converter circuit, said inverter circuit comprising a pair of magnetically coupled reactors each having first and second terminals, said first terminals connected to respective terminals of the input of said magnetically coupled reactors; means for connection of each series connection point of said separation thyristor unit to respective star-connected armature coils of an AC motor as a load; circulation thyristors connected in series between the respective input terminals of said inverter circuit; and means to connect the series connection point of the circulation thyristors to the neutral point of the star-connected armature coils of the AC motor; whereby said separation thyristors and said circulation thyristors of said inverter circuit are rendered conductive and controlled in accordance with a predetermined sequence, respectively, and said polyphase thyristor bridge rectifier circuit and said chopper elements are rendered conductive or nonconductive as necessary to render the output voltage of said converter circuit positive, negative or zero to effect commutation and current control.

Claim 7

An AC--AC converter device as claimed in claim 3, wherein said chopper unit comprises: a first chopper element including a parallel combination of a first transistor and a first Zener diode connected to the DC output side of said rectifier circuit having a self-commutating action; and a second chopper element including a parallel combination of a second transistor and a second Zener diode connected between said first chopper element and said current blocking diode having a self-commutating action.

Claim 8

An AC--AC converter device as claimed in claim 3, wherein said chopper unit comprises: a first chopper element including a first thyristor, having a first diode anti-parallel connected thereto, connected to the DC output side of said rectifier circuit; a second chopper element including a second thyristor, having a second diode anti-parallel connected thereto, connected between said first thyristor and said current blocking diode; and a series combination of a commutating capacitor and a commutating reactor connected between said first and the second chopper elements.

Claim 9

An AC--AC converter device as claimed in claim 3, wherein said chopper unit comprises: a first chopper element including an electronic switch connected to the DC output side of said rectifier circuit; and a second chopper element including a parallel combination of a non-linear resistor element and a bypass thyristor connected between said first chopper element and said current blocking diode.

Claim 10

An AC--AC converter device comprising: a converter circuit for connection to a source of polyphase alternating current capable of instantaneously varying an output voltage to a positive voltage, a negative voltage or zero, said converter circuit comprising a plurality of compensating reactors for connection to respective phases of the source of polyphase alternating current; a discharge blocking diode bridge circuit connected to the source of polyphase alternating current through said compensating reactors; first and second commutating circuits each consisting of a series combination of a capacitor and a reactor connected to respective DC outputs of said discharge blocking diode bridge circuits; and first and second rectifier circuits each consisting of a first thyristor and a first diode anti-parallel connected thereto which are connected between the outputs of the converter and said first and the second commutating circuits, respectively; and a coupled reactor commutating inverter circuit cascade-connected to said converter circuit, said inverter circuit having a plurality of thyristors which are rendered conductive in a predetermined sequence, whereby said output voltage of said converter circuit is rendered positive, negative or zero as necessary to effect commutation and current control in said inverter circuit.

Claim 11

An AC--AC converter device comprising: a converter circuit for connection to a source of polyphase alternating current capable of instantaneously varying an output voltage to a positive voltage, a negative voltage or zero, said converter circuit comprising a plurality of compensating reactors for connection to respective phases of the source of polyphase alternating current; a discharge blocking diode bridge circuit connected to the source of polyphase alternating current through said compensating reactors; first and second commutating circuits each consisting of a series combination of a capacitor and a reactor connected to respective DC outputs of said discharge blocking diode bridge circuits; and first and second rectifier circuits each consisting of a first thyristor and a first diode anti-parallel connected thereto which are connected between the outputs of the converter and said first and the second commutating circuits, respectively; and a coupled reactor commutating inverter circuit cascade-connected to said converter circuit, said inverter circuit having a plurality of thyristors which are rendered conductive in a predetermined sequence, whereby said output voltage of said converter circuit is rendered positive, negative or zero as necessary to effect commutation and current control in said inverter circuit.