Multi-phase thyristor inverter

Claim 2

Multi-phase thyristor inverter adapted to be connected to a source of d-c potential and providing multi-phase a-c output comprising two similar groups (50, 60, 70; 53, 63, 73) of at least two thyristors each, the thyristors of one group being connected to the positive potential of the source and the thyristors of the other group being connected to the negative potential of the source, the groups of the thyristors being connected to provide multi-phase full-wave output (S, R, T); a pair of switchable turn-off circuits (30-34; 40-44) having bipolar outputs, the output of one switchable turn-off circuit being connected to all thyristors of a respective group and the output of the other switchable turn-off circuit being connected to all the thyristors of the other group to extinguish the thyristors in the respective group after firing thereof; back-current diodes (51, 61, 71; 52, 62, 72) directly connected in opposite polarity in circuit with the respective thyristors and the d-c source, the output for each phase (S, R, T) being taken from the interconnection (59, 96, 97) between the respective thyristor and the associated back-current diode; and current sensing means (54, 64, 74; 93, 94) coupled to said interconnection to sense the total current flowing in a respective phase, the current sensing means having a common output (92) to provide an output signal representative of total current flow in the respective phases.

Claim 3

Inverter according to claim 1, for use in a three-phase network to supply a motor, comprising at least three thyristors for each group, one of each being connected to a phase of a respective phase winding of the motor; the common output (92) from the current sensing means providing an output signal representative of total current flow in the motor.

Claim 4

Inverter according to claim 1, wherein the current sensing means comprises a core (93) having an air gap and conductors (95, 96, 97) carrying the currents of all the phases of the motor coupled to the core so that the flux through the core will be representative of total motor current; and a Hall detector (94) in said gap, the Hall detector providing said output signal.

Claim 5

Inverter according to claim 1, comprising a pair of commutating reactors (13, 14; 16, 17), one each in series connection between the source of d-c potential and the positive and negative supply to the groups of thyristors, said reactors having secondary windings (14, 17), the secondary windings and the reactor being associated with a common core; and a series of interconnections between the positive (11) and the negative (12) terminals of the source, each being connected to a respective secondary winding (14, 17) and a blocking diode (22, 23) connected to the other terminal of the secondary winding and poled in blocking direction with respect to the d-c source.

Claim 6

Inverter according to claim 1, including common connected diodes (24, 27) poled similarly as said back current diodes interconnecting said back current diodes and the positive and negative terminals of the source.

Claim 7

Inverter according to claim 5, comprising a pair of commutating reactors (13, 14; 16, 17), one each in series connection between the source of d-c potential and the positive and negative supply of the groups of thyristors, said reactors having secondary and tertiary windings (15, 18), and respective tertiary diodes (25, 26) connected with the respective tertiary winding and to the junction of the common connected diode (22, 27) and the back current diodes (51, 61, 71; 52, 62, 72).

Claim 8

D-c to three-phase a-c inverter in combination with an a-c motor having at least three phase windings comprising two groups of at least three thyristors each (50, 60, 70; 53, 63, 73), each group of thyristors supplying a half wave of the three phase supply to the motor, the thyristors of each group being connected with one terminal to a respective terminal of the d-c source, the other terminals of the thyristor being connected to a phase winding (80, 81, 82) of the motor; and two turn-off circuits, one for each group of thyristors, one each circuit being common to the thyristors of each group and comprising switchable quenching condenser means (30-34; 40-44) and diode means (51, 61, 71; 52, 62, 72) one for each of the turn-off circuits and the groups of the thyristors, the diode means being poled oppositely with respect to each other and to the thyristors to permit turn-off voltage from the turn-off circuits to be applied to all the thyristors of a group and to extinguish the thyristors of the group supplying opposite half waves to the motor windings; a commutating reactance in series with the connection from the d-c supply to the one terminal of the thyristors, said commutating reactance having an additional winding (15, 18) poled similarly to the series-connected winding; and diode means (24, 26; 25, 27) similarly poled and interconnecting the additional winding with said diode means and the terminals of the d-c source, said diode means being poled to permit gradual decay of current flow due to change of current flow through the commutating reactance and thus extend current flow through the windings of the motor.

Claim 9

D-c to three-phase a-c inverter in combination with an a-c motor having at least three phase windings comprising two groups of at least three thyristors each (50, 60, 70; 53, 63, 73), each group of thyristors supplying a half wave of the three phase supply to the motor, the thyristors of each group being connected with one terminal to a respective terminal of the d-c source, the other terminals of the thyristor being connected to a phase winding (80, 81, 82) of the motor; and two turn-off circuits, one for each group of thyristors, one each circuit being common to the thyristors of each group and comprising switchable quenching condenser means (30-34; 40-44) and diode means (51, 61, 71; 52, 62, 72) one for each of the turn-off circuits and the groups of the thyristors, the diode means being poled oppositely with respect to each other and to the thyristors to permit turn-off voltage from the turn-off circuits to be applied to all the thyristors of a group and to extinguish the thyristors of the group supplying opposite half waves to the motor windings; a commutating reactance in series with the connection from the d-c supply to the one terminal of the thyristors, said commutating reactance having an additional winding (15, 18) poled similarly to the series-connected winding; and diode means (24, 26; 25, 27) similarly poled and interconnecting the additional winding with said diode means and the terminals of the d-c source, said diode means being poled to permit gradual decay of current flow due to change of current flow through the commutating reactance and thus extend current flow through the windings of the motor.