Zero-crossing silicon controlled rectifier control system

Claim 3

A system as recited in claim 1 wherein said triggering means comprises a first trigger circuit coupled to said pulse generating means and the source for causing the first main silicon controlled rectifier to conduct for causing a second half cycle to energize the load when a command signal exists and a second trigger circuit couple to the source and the load and responsive to load energization by the second half cycle to cause the second silicon controlled rectifier to conduct the next succeeding half cycle.

Claim 4

A system as recited in claim 1 wherein the source generates a three-phase voltage and the load is a three-phase load coupled thereto by a back-to-back silicon controlled rectifier and diode in each phase, said trigger means comprising a first trigger circuit coupled to said pulse generating means and to the source for causing the first main silicon controlled rectifier in the first phase to conductive during the next succeeding phase cycle when the main silicon controlled rectifier is forward biased and second and third trigger circuits coupled to the load and individually to said second and third main silicon controlled rectifiers respectively and responsive to energization of the load to cause the said second and third main silicon controlled rectifiers to energize the load in sequence whereby the load is energized by a full three-phase cycle.

Claim 7

A system as recited in claim 4 wherein said pulse generating means includes a direct current voltage source, wherein said first switching means includes a pair of complementary transistors in series with said voltage source and connected to said integrating means, said complementary transistors being biased to conduction by time inter integral signals of a given polarity.

Claim 8

A system as recited in claim 5 wherein said second switching means includes another transistor in series with said voltage source and coupled to the alternating current source to be biased for conduction during each half wave of the same polarity as the first half wave, said other transistor being turned off before the end of conductive half wave.

Claim 9

A system as recited in claim 6 wherein said pulse generator additionally comprises inductive and capacitive impedances in parallel, said inductive impedance being coupled to said triggering means to generate a pulse at the end of conductive half waves during which the first switching means is conductive when the other transistor in said second switching means is turned off.

Claim 10

A system as recited in claim 7 wherein said inductive impedance includes a transformer having primary and secondary windings said primary winding being in series with said first and second switching means and said secondary winding being connected to said trigger means.

Claim 11

A system as recited in claim 8 wherein said trigger means comprises a first pilot circuit including a first pilot silicon controlled rectifier coupled to said first main silicon controlled rectifier and means coupled to the source for biasing said first pilot silicon controlled rectifier for conduction and means connected to said pulse generating means transformEr secondary, said first pilot silicon controlled rectifier being responsive to a pulse to turn on said first main silicon controlled rectifier and energize the load and a second pilot coupled to the load and responsive to load energization to turn on said second main silicon controlled rectifier.

Claim 12

A system as recited in claim 9 adapted for operation in a single phase full wave control system wherein said second pilot comprises a second pilot silicon controlled rectifier and means coupled to the source for biasing said second pilot silicon controlled rectifier for conduction and means adapted to be coupled to the load ro to generate a signal in response to load energization, said means being coupled to said second pilot silicon controlled rectifier.

Claim 13

A zero-crossing power control system for coupling an alternating current, single-phase, full-wave electrical load and source comprising: a. first and second oppositely poled, parallel, main silicon controlled rectifiers, b. command signal generating a means including i. means for generating a control signal variable in accordance with a desired average power to the load, ii. means for generating a feedback signal variable in accordance with an actual average power to the load during a first half cycle, and iii. means for integrating the sum of the control and feedback signals to thereby generate the command signal, c. a direct current source, d. a first switch responsive to predetermined values of said command signal including first and second complementary transistors coupled to said command signal generating means and said direct current source, e. a pulse generator including a serially connected transformer primary and resistor and a capacitor in parallel therewith, said pulse generator being connected to said first switch, f. a second switch coupling said pulse generator to said direct current source and being coupled to the source to be conductive during second half cycles, said transformer primary being energized when said first and second switches are conductive, and g. a trigger circuit responsive to deenergization of said pulse generator to cause said first and second main silicon controlled rectifiers to fire sequentially including i. a first pilot circuit including a first pilot silicon controlled rectifier coupled to said first main silicon controlled rectifier and means coupled to the source for biasing said first pilot silicon controlled rectifier for conduction and means connected to said pulse generating means transformer for applying a signal to said first pilot silicon controlled rectifier to cause said first main silicon controlled rectifier to begin conduction at the next succeeding positive zero crossing, and ii. a second pilot circuit including a second pilot silicon controlled rectifier coupled to the second main silicon controlled rectifier, means coupled to the source for biasing said second pilot silicon controlled rectifier for conduction and means adapted to be coupled to the load to generate a signal in response to load energization to cause said second pilot silicon controlled rectifier to be conductive to thereby cause the next succeeding half cycle to be coupled to the load through the second main silicon controlled rectifier.

Claim 14

A zero-crossing power control system for coupling an alternating current, single-phase, full-wave electrical load and source comprising: a. first and second oppositely poled, parallel, main silicon controlled rectifiers, b. command signal generating a means including i. means for generating a control signal variable in accordance with a desired average power to the load, ii. means for generating a feedback signal variable in accordance with an actual average power to the load during a first half cycle, and iii. means for integrating the sum of the control and feedback signals to thereby generate the command signal, c. a direct current source, d. a first switch responsive to predetermined values of said command signal including first and second complementary transistors coupled to said command signal generating means and said direct current source, e. a pulse generator including a serially connected transformer primary and resistor and a capacitor in parallel therewith, said pulse generator being connected to said first switch, f. a second switch coupling said pulse generator to said direct current source and being coupled to the source to be conductive during second half cycles, said transformer primary being energized when said first and second switches are conductive, and g. a trigger circuit responsive to deenergization of said pulse generator to cause said first and second main silicon controlled rectifiers to fire sequentially including i. a first pilot circuit including a first pilot silicon controlled rectifier coupled to said first main silicon controlled rectifier and means coupled to the source for biasing said first pilot silicon controlled rectifier for conduction and means connected to said pulse generating means transformer for applying a signal to said first pilot silicon controlled rectifier to cause said first main silicon controlled rectifier to begin conduction at the next succeeding positive zero crossing, and ii. a second pilot circuit including a second pilot silicon controlled rectifier coupled to the second main silicon controlled rectifier, means coupled to the source for biasing said second pilot silicon controlled rectifier for conduction and means adapted to be coupled to the load to generate a signal in response to load energization to cause said second pilot silicon controlled rectifier to be conductive to thereby cause the next succeeding half cycle to be coupled to the load through the second main silicon controlled rectifier.

Claim 15

A zero crossing power controlled system for coupling an alternating current, three-phase electrical load and source comprising: a. a plurality of main firing circuits, each firing circuit including a main silicon controlled rectifier and an oppositely poled diode in parallel and being in series with one phase of the source and load, b. command signal generating means including means for generating a control signal variable in accordance with the desired average power to the load, means for generating a feedback signal variable in accordance with an actual average power to the load during a first half cycle and means for integrating the sum of the control and feedback signals to thereby gEnerate the command signal, c. a direct current source, d. a first switch responsive to predetermined values of said command signal including first and second complementary transistors coupled to said command signal generating means and said direct current source, e. a pulse generator including a serially connected transformer primary and resistor and a capacitor in parallel therewith, said pulse generator being connected to said first switch, f. a second switch coupling said pulse generator to said direct current source and being coupled to the source to be conductive to define a decision time, said second switch including third and fourth transistors coupled to be energized by different phases of the source, said fourth transistor controlling the conduction of said third transistor, said third transistor connecting said pulse generator to said direct current source, and g. a trigger circuit responsive to deenergization of said pulse generator to cause said plurality of main silicon controlled rectifiers to fire sequentially including i. a first pilot circuit including first and second pilot silicon controlled rectifiers oppositely poled and connected in parallel, said pilot silicon controlled rectifiers being connected in series with a transformer load, said first pilot silicon controlled rectifier being rendered conductive to energize said transformer and said second pilot silicon controlled rectifier being energized during the next half cycle, said transformer and said pilot circuit coupling the voltage to said first main silicon controlled rectifier, ii. a second pilot circuit coupled to said load and said second main silicon controlled rectifier to bias said second main silicon controlled rectifier for firing, and iii. a third control circuit coupled to said load and said third main silicon controlled rectifier to bias said third main silicon controlled rectifier for firing in response to load energization whereby a pulse from said pulse generator causes said main silicon controlled rectifiers to be fired in sequence.

Claim 16

A zero crossing power controlled system for coupling an alternating current, three-phase electrical load and source comprising: a. a plurality of main firing circuits, each firing circuit including a main silicon controlled rectifier and an oppositely poled diode in parallel and being in series with one phase of the source and load, b. command signal generating means including means for generating a control signal variable in accordance with the desired average power to the load, means for generating a feedback signal variable in accordance with an actual average power to the load during a first half cycle and means for integrating the sum of the control and feedback signals to thereby gEnerate the command signal, c. a direct current source, d. a first switch responsive to predetermined values of said command signal including first and second complementary transistors coupled to said command signal generating means and said direct current source, e. a pulse generator including a serially connected transformer primary and resistor and a capacitor in parallel therewith, said pulse generator being connected to said first switch, f. a second switch coupling said pulse generator to said direct current source and being coupled to the source to be conductive to define a decision time, said second switch including third and fourth transistors coupled to be energized by different phases of the source, said fourth transistor controlling the conduction of said third transistor, said third transistor connecting said pulse generator to said direct current source, and g. a trigger circuit responsive to deenergization of said pulse generator to cause said plurality of main silicon controlled rectifiers to fire sequentially including i. a first pilot circuit including first and second pilot silicon controlled rectifiers oppositely poled and connected in parallel, said pilot silicon controlled rectifiers being connected in series with a transformer load, said first pilot silicon controlled rectifier being rendered conductive to energize said transformer and said second pilot silicon controlled rectifier being energized during the next half cycle, said transformer and said pilot circuit coupling the voltage to said first main silicon controlled rectifier, ii. a second pilot circuit coupled to said load and said second main silicon controlled rectifier to bias said second main silicon controlled rectifier for firing, and iii. a third control circuit coupled to said load and said third main silicon controlled rectifier to bias said third main silicon controlled rectifier for firing in response to load energization whereby a pulse from said pulse generator causes said main silicon controlled rectifiers to be fired in sequence.