Electric welder that uses magnetic amplifier to supply firing signals for controlled rectifier |
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| 申请号 | US3564333D | 申请日 | 1968-02-21 | 公开(公告)号 | US3564333A | 公开(公告)日 | 1971-02-16 |
| 申请人 | NAT STANDARD CO; | 发明人 | CRAMER DONALD W; BECKER EUGENE W; MEYER RICHARD E; REINERT OWEN E; | ||||
| 摘要 | The high frequency voltages, that are customarily used to help initiate the arcs of electric welders, tend to cause premature and erratic initiation of those arcs where those electric welders use silicon controlled rectifiers to control the amounts of power supplied to those arcs and use transistor-type firing circuits to control the firing angles of those silicon controlled rectifiers; because transistor-type firing circuits are sensitive to high frequency voltages. The present invention provides an electric welder which utilizes silicon controlled rectifiers to control the amounts of power supplied to arcs and yet avoids premature and erratic initiation of those arcs by using a magnetic amplifier to control the firing angles of those silicon controlled rectifiers. Also, the present invention keeps that electric welder from supplying undesirably high amounts of power to those arcs, during the initiation of those arcs, by biasing the magnetic core of that magnetic amplifier downwardly at the conclusion of each welding operation. In addition, the electric welder of the present invention has a one-turn winding, on the magnetic core of the magnetic amplifier thereof, through which all of the welding current flows; and that one-turn winding is part of a feedback circuit for that magnetic amplifier which enables that electric welder to vary the amounts of power supplied to an arc over the full range of firing angles of the silicon controlled rectifiers thereof by merely adjusting a single control of that magnetic amplifier. | ||||||
| 权利要求 | 1. An electric welder which comprises: a controlled rectifier that has a cathode and an anode and a gate and that can respond to the application of firing signals to said gate to make the anode-cathode circuit thereof become conductive. a magnetic amplifier that has a plurality of input windings and that has an output winding which can develop firing signals, said output winding of said magnetic amplifier being connected to said gate of said controlled rectifier, said magnetic amplifier selectively causing said output winding thereof to supply firing signals to said gate of said controlled rectifier to render said anode-cathode circuit of said controlled rectifier conductive, output terminals that are connectable to an electrode and to a workpiece and that are connected to a source of AC by said anode-cathode circuit of said controlled rectifier, said output terminals connecting said electrode and said workpiece and said anode-cathode circuit of said controlled rectifier to series relation across said source of AC to enable said electrode and said workpiece to receive energy, said controlled rectifier permitting only unidirectional current to flow through said anode-cathode circuit thereof, and thereby causing the energy supplied to said electrode and to said workpiece to be DC energy, a source of high-frequency voltages connected in series relation with said output terminals and said electrode and said workpiece and said output winding of said magnetic amplifier and said anode-cathode circuit of said controlled rectifier to supply high-frequency voltages to said output terminals and thereby help initiate and establish an arc between said electrode and said workpiece; said magnetic amplifier having at least one of the input windings thereof connected to said output terminals whereby the current flowing through said one input winding is subject to said high-frequency voltages supplied to said output terminals by said source of high-frequency voltages, but said magnetic amplifier having substantial inductance and thereby enabling said output winding, and the firing angles which said output winding supplies to said gate of said controlled rectifier, to be substantially insensitive to the high-frequency voltages applied to said output terminals by said source of highfrequency voltages, and whereby said electric welder makes the firing of said controlled rectifier independent of, and insensitive to, said highfrequency voltages developed by said source of high-frequency voltages. 2. An electric welder as claimed in claim 1 wherein a relay has contacts that are connected to said source of high-frequency voltages and that are selectively actuated to cause said source of high-frequency voltages to supply high-frequency voltages to said output terminals and thereby help initiate and establish an arc between said electrode and said workpiece, said relay having a finite energizing time that is longer than the duration of transients developed by said output winding of said magnetic amplifier at ''''turn on,'''' whereby said transients can not cause said arc to pit, perforate or melt said workpiece as said arc is initiated. 3. An electric welder as claimed in claim 1 wherein a relay has contacts that are connected to said source of high-frequency voLtages and that are selectively actuated to cause said source of high-frequency voltages to supply high-frequency voltages to said output terminals and thereby help initiate and establish an arc between said electrode and said workpiece, said relay having a finite energizing time that is longer than the duration of transients developed by said output winding of said magnetic amplifier at ''''turn on,'''' whereby said transients can not cause said arc to pit, perforate or melt said workpiece as said arc is initiated, the coil of said relay being connected across said output terminals and thus being responsive to the voltage across said output terminals, said output terminals having a relatively large voltage appearing thereacross prior to the establishing of an arc between said electrode and said workpiece and said relay responding to said voltage to actuate said contacts and thereby cause said source of high-frequency voltages to supply high-frequency voltages to said output terminals, said voltage across said output terminals decreasing when an arc is established and said relay automatically responding to decrease in said voltage as an arc is established to deactuate said source of high-frequency voltages, whereby said source of high-frequency voltages will, prior to the establishing of a arc, supply high-frequency voltages to said output terminals to help initiate and establish an arc between said electrode and said workpiece but will then automatically be deactuated. 4. An electric welder which comprises: a controlled rectifier that has a cathode and an anode and a gate and that can respond to the application of firing signals to said gate to make the anode-cathode circuit thereof become conductive, a magnetic amplifier that has a plurality of input windings and that has an output winding which can develop firing signals, said output winding of said magnetic amplifier being connected to said gate of said controlled rectifier to selectively supply firing signals to said gate of said controlled rectifier to render said anode-cathode circuit of said controlled rectifier conductive, output terminals that are connectable to an electrode and a workpiece and that are connected to said anode-cathode circuit of said controlled rectifier to receive energy from said controlled rectifier, a transformer that supplies a predetermined voltage to one terminal thereof and that supplies a high voltage to a second terminal thereof, said output terminals connecting said electrode and said workpiece in series relation with said anode-cathode circuit of said controlled rectifier and with said one terminal of said transformer, a capacitor that is connected to said second terminal of said transformer and that coacts with said transformer to act as a current source, said current source being connected to at least one input winding of said magnetic amplifier to supply substantially ripple-free current to said one input winding whenever said transformer is developing said higher voltage at said second terminal, and said one input winding of said magnetic amplifier responding to the flow of said substantially ripple-free current therethrough to cause said output winding of said magnetic amplifier to develop and supply closely controlled firing signals to said gate of said controlled rectifier. 5. An electric welder as claimed in claim 4 wherein said current source is connected to said one input winding of said magnetic amplifier by one section of a potentiometer, whereby the value of the current flowing through said one input winding of said magnetic amplifier from said current source can readily be varied by adjusting the setting of the movable contact of said potentiometer. 6. An electric welder as claimed in claim 4 wherein said current source is connected to said one input winding of said magnetic amplifier by one section of a potentiometer, whereby the value of the current flowing through said one input winding of said magnetic amplifier fRom said current source can readily be varied by adjusting the setting of the movable contact of said potentiometer, and wherein a voltage-regulating element is connected in parallel with said potentiometer and receives current from said current source, said current source applying sufficient voltage to said voltage-regulating element, whenever said transformer is developing said higher voltage at said second terminal, to enable said voltage-regulating element to maintain a predetermined voltage across said potentiometer prior to, during, and after the initiation and establishment of an arc. 7. An electric welder as claimed in claim 4 wherein said current source also is connected to a second input winding of said magnetic amplifier to supply substantially ripple-free current to said second input winding whenever said transformer is developing said higher voltage at said second terminal, said one winding of said magnetic amplifier being a bias winding of said magnetic amplifier and said second winding of said magnetic amplifier being a control winding of said magnetic amplifier. 8. An electric welder as claimed in claim 4 wherein said current source also is connected to a second input winding of said magnetic amplifier to supply substantially ripple-free current to said second input winding whenever said transformer is developing said higher voltage at said second terminal, said one winding of said magnetic amplifier being a bias winding of said magnetic amplifier and said second winding of said magnetic amplifier being a control winding of said magnetic amplifier, wherein a first means controls the value of the current flowing from said current source through said one winding of said magnetic amplifier, and wherein a second means controls the value of the current flowing from said current source through said second winding of said magnetic amplifier, said first said and said second means being individually adjustable to permit selective adjustments of the currents flowing from said current source through said one winding of said magnetic amplifier and through said second winding of said magnetic amplifier. 9. An electric welder as claimed in claim 4 wherein said current source is connected to said one input winding of said magnetic amplifier by a means that is adjustable to control the value of the current flowing from said current source through said one input winding of said magnetic amplifier, and wherein said current source is connected to said output terminals to cause current therefrom to flow through said output terminals and thus through any arc developed between said electrode and said workpiece. 10. An electric welder which comprises: a controlled rectifier that has a cathode and an anode and a gate and that can respond to the application of firing signals to said gate to make the anode-cathode circuit thereof become conductive, a magnetic amplifier that has a plurality of input windings and that has an output winding which can develop firing signals, said output winding of said magnetic amplifier being connected to said gate of said controlled rectifier; said magnetic amplifier selectively causing said output winding thereof to supply firing signals to said gate of said controlled rectifier to render said anode-cathode circuit of said controlled rectifier conductive, output terminals that are connectable to an electrode and to a workpiece and that are connected to a source of power by said anode-cathode circuit of said controlled rectifier, said output terminals connecting said electrode and said workpiece and said anode-cathode circuit of said controlled rectifier to series relation across said source of power to enable said electrode and said workpiece to receive energy, said magnetic amplifier having a start-bias winding that responds to current flow therethrough to reduce the ''''on'''' time of said output winding of said magnetic amplifier, and thus to reduce the ''''on'''' time of said anode-cathode cIrcuit of said controlled rectifier; and a contact-free sensing element that is connected to said start-bias winding of said magnetic amplifier and to said output terminals and that permits current to flow through said start-bias winding prior to the initiation and establishment of an arc between said electrode and said workpiece but that keeps current from flowing through said start-bias winding after the initiation and establishment of an arc between said electrode and said workpiece. 11. An electric welder as claimed in claim 10 wherein said contact-free sensing element is voltage-sensitive and is connected across said output terminal to sense the voltage across said output terminals prior to, during, and after the initiation and establishment of an arc between said electrode and said workpiece, said contact-free sensing element being a solid state element. 12. An electric welder as claimed in claim 10 wherein said contact-free sensing element is a Zener diode and is connected across said output terminals to sense the voltage across said output terminals. 13. An electric welder as claimed in claim 10 wherein a transformer supplies a predetermined voltage to one terminal thereof and supplies a higher voltage to a second terminal thereof, wherein said one terminal of said transformer is said source of power and said controlled rectifier is connected to said one terminal of said transformer, wherein a capacitor is connected to said second terminal of said transformer and coacts with said transformer to act as a current source, wherein said current source is connected to said output terminals and supplies a minimum value of current to said output terminals after the initiation and establishment of an arc between said electrode and said workpiece, and wherein an adjustable element can coact with said contact-free sensing element and with said start-bias winding of said magnetic amplifier to set the current flowing through said start-bias winding at a level which will cause the ''''on'''' time of said output winding of said magnetic amplifier and the ''''on'''' item of said anode-cathode circuit of said controlled rectifier to be short enough to hold the total current supplied to said output terminals by said current source and by said anode-cathode circuit of said controlled rectifier during the initiation and establishment of said arc between said electrode and said workpiece to levels close to said minimum value of current. 14. An electric welder which comprises: a controlled rectifier that has a cathode and an anode and a gate and that can respond to the application of firing signals to said gate to make the anode-cathode circuit thereof become conductive; a magnetic amplifier that has a plurality of input windings and that has an output winding which can develop firing signals, said output winding of said magnetic amplifier being connected to said gate of said controlled rectifier, said magnetic amplifier selectively causing said output winding thereof to supply firing signals to said gate of said controlled rectifier to render said anode-cathode circuit of said controlled rectifier conductive; output terminals that are connectable to an electrode and to a workpiece and that are connected to a source of power by said anode-cathode circuit of said controlled rectifier; said output terminals connecting said electrode and said workpiece and said anode-cathode circuit of said controlled rectifier in series relation across said source of power to enable said electrode and said workpiece to receive energy, and means including one of said input windings of said magnetic amplifier to drive the flux density of the magnetic core of said magnetic amplifier downwardly toward the bottom of the hysteresis loop of said magnetic core at the termination of each welding operation. 15. An electric welder as claimed in claim 14 wherein said means also includes a capacitor which is charged up during the maintenance of an arc between Said electrode and said workpiece, and wherein said one input winding of said magnetic amplifier responds to current flowing therethrough from said capacitor to drive the flux density of the magnetic core of said magnetic amplifier downwardly toward the bottom of the hysteresis loop of said magnetic core. 16. An electric welder as claimed in claim 14 wherein said means also includes a capacitor which is charged up during the maintenance of an arc between said electrode and said workpiece, wherein said one input winding is the bias winding of said magnetic amplifier, and wherein said means further includes a unidirectional element in the charging circuit of said capacitor which keeps said capacitor from discharging through said charging circuit and which forces said capacitor to discharge through said bias winding and thereby drive the flux density of the magnetic core of said magnetic amplifier downwardly toward the bottom of the hysteresis loop of said magnetic core. 17. An electric welder which comprises: a controlled rectifier that has a cathode and an anode and a gate and that can respond to the application of firing signals to said gate to make the anode-cathode circuit thereof become conductive; a second controlled rectifier that has a cathode and an anode and a gate and that can respond to the application of firing signals to said gate to make the anode-cathode circuit thereof become conductive; a transformer interconnected with, and supplying power to, the anode-cathode of both of said controlled rectifiers; a magnetic amplifier that has the output thereof connected to, and supplying firing signals to, said gates of both of said controlled rectifiers; an inductor that is connected in series relation with an electrode and a workpiece and the anode-cathode circuits of both of said controlled rectifiers so the currents flowing through said electrode and workpiece and anode-cathode circuits of both of said controlled rectifiers also flow through it; and said inductor keeping each of said controlled rectifiers from adversely affecting the firing angle of the other of said controlled rectifiers although said anode-cathode circuits of both of said controlled rectifier s are connected to the same transformer and electrode nd workpiece although said gates of both of said controlled rectifiers are connected to the output of the same magnetic amplifier. 18. An electric welder as claimed in claim 17 wherein said controlled rectifiers have the anodes thereof connected together and wherein said inductor is connected to said anodes, wherein a flyback diode is connected in parallel relation with said interconnected transformer and said anode-cathode circuits of both of said controlled rectifiers, and wherein said inductor and said flyback diode tend to keep current flowing through an arc between said electrode and said workpiece during those periods when said anode-cathode circuits of both of said controlled rectifiers are ''''off.'''' 19 An electric welder which comprises: A controlled rectifier that has a cathode and an anode and a gate and that can respond to the application of firing signals to said gate to make the anode-cathode circuit thereof become conductive; a magnetic amplifier that has a plurality of input windings and that has an output winding which can develop firing signals; said output winding of said magnetic amplifier being connected to said gate of said controlled rectifier; said magnetic amplifier selectively causing said output winding thereof to supply firing signals to said gate of said controlled rectifier to render said anode-cathode circuit of said controlled rectifier conductive; output terminals that are connectable to an electrode and to a workpiece and that are connected to said anode-cathode circuit of said controlled rectifier to receive energy from said controlled rectifier; a transformer that supplies a predetermined voltage to one terminal thereof and that supplies a higher Voltage to a second terminal thereof; said output terminals connecting said electrode and said workpiece to series relation with said anode-cathode circuit of said controlled rectifier and with said one terminal of said transformer; and means connecting said second terminal of said transformer to one of said output terminals to enable said second terminal of said transformer to supply said higher voltage to said output terminals and thereby facilitates the initiation and establishment of an arc between said electrode and said workpiece. 20. An electric welder as claimed in claim 19 wherein said means includes a unidirectional element to enable said means to supply DC voltage to said one output terminal, said means also including an adjustable impedance to permit the value of the current flowing through said means after the initiation and establishment of an arc between said electrode and said workpiece to be varied. 21. An electric welder which comprises: a controlled rectifier that has a cathode and an anode and a gate and that can respond to the application of firing signals to said gate to make the anode-cathode circuit thereof become conductive; a magnetic amplifier that has a plurality of input windings and that has an output winding which can develop firing signals; said output winding of said magnetic amplifier being connected to said gate of said controlled rectifier; said magnetic amplifier selectively causing said output winding thereof to supply firing signals to said gate of said controlled rectifier to render said anode-cathode circuit of said controlled rectifier conductive; output terminals that are connectable to an electrode and to a workpiece and that are connected to a source of power by said anode-cathode circuit of said controlled rectifier; said output terminals connecting said electrode and said workpiece and said anode-cathode circuit of said controlled rectifier in series relation across said source of power to enable said electrode and said workpiece to receive energy; one of said input windings of said magnetic amplifier being a feedback winding; a feedback circuit that includes said feedback winding of said magnetic amplifier; and said feedback winding of said magnetic amplifier being a one-turn winding. 22. An electric welder as claimed in claim 21 wherein said magnetic amplifier is a toroid and wherein said one-turn feedback winding is a rodlike element that extends through the cylindrical space defined by said magnetic amplifier. 23. An electric welder as claimed in claim 21 wherein said one-turn feedback winding is connected to said output terminals to have all of the welding current supplied by said electric welder pass through it. 24. an electric welder as claimed in claim 21 wherein said one-turn winding is a rodlike element that supports said magnetic amplifier. 25. An electric welder which comprises: a controlled rectifier that has a cathode and an anode and a gate and that can respond to the application of firing signals to said gate to make the anode-cathode circuit thereof become conductive; a magnetic amplifier that has a plurality of input windings and that has an output winding which can develop firing signals; said output winding of said magnetic amplifier being connected to said gate of said controlled rectifier; said magnetic amplifier selectively causing said output winding thereof to supply firing signals to said gate of said controlled rectifier to render said anode-cathode circuit of said controlled rectifier conductive; output terminals that are connectable to an electrode and to a workpiece and that are connected to said anode-cathode circuit of said controlled rectifier to receive energy from said controlled rectifier; terminals to supply alternating current to said output winding of said magnetic amplifier; one of said input windings of said magnetic amplifier being a response winding which has the terminals Thereof shorted; and said response winding providing a time response for said magnetic amplifier, and thus for said electric welder, which is long enough to enable said electric welder to be stable in operation. 26. An electric welder as claimed in claim 25 wherein said response winding is a multiturn winding, and wherein said time response for said magnetic amplifier makes the time response for said electric welder longer than a plurality of the cycles of the alternating current supplied to said output winding of said magnetic amplifier. 27. An electric welder which comprises: a variable impedance element that can be connected in series relation with a source of alternating current and with an electrode and a workpiece to supply welding current to said electrode and workpiece; said variable impedance element having a portion thereof which can respond to a bias applied thereto to set an operating parameter of said variable impedance element; said variable impedance element having a second portion thereof which can respond to a control current supplied thereto to set a second operating parameter of said variable impedance element; a voltage source and a capacitor which are connected to said electrode and said workpiece and which coact to supply low ripple direct current to said electrode and workpiece to help maintain an arc therebetween; said voltage source of said capacitor being connected to said second portion of said variable impedance element to supply said control current to said second portion of said variable impedance element; and said voltage source and said capacitor being connected to the first said portion of said variable impedance element to apply said bias to said first said portion of said variable impedance element. |
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