MXPA00004571A - Welding power supply for pulsed spray welding - Google Patents

Abstract

An arc welding machine is disclosed for providing a continuous feed electrode to a weld site. The arc welding machine includes a line frequency transformer (52) having a primary winding (64), a first secondary winding (66), and a second secondary winding (68) (e.g., an extension winding, a separate winding, etc.). The first secondary winding (66) provides a welding power having a first voltage at a welding power output terminal (76). The second secondary winding (68) provides a second welding power having a second higher voltage at an input terminal of a switch (80), the switch (80) being controlled to provide a pulsed power at the welding power output terminal (76). According to one feature, the arc welding machine produces a pulsed power having a fixed pulse width and a fixed frequency, the fixed pulse width and fixed frequency being substantially free of operator adjustment.

Description

SUPPLY OF ENERGY FOR PULSOS JET WELDING FIELD OF THE INVENTION The present invention relates in general to Power supplies for welding machines and, more specifically, with power supplies for welding machines to provide a jet welding technique with pulse jet. ANTECENT OF THE INVENTION Various methods for welding are known in the art, each with its own advantages and disadvantages.

Common welding processes include gas welding, oxiacetal welding, protected arc welding (SMMT) or welding "with electrode", welding with inert gas (MIG) or "wire feed" welding, and inert gas tungsten welding (GTAW) or "TIG" welding. MIG welding is remarkable for its simplicity and speed. Although the device of the present invention is described in reference to a supply of MIG welding energy, the person skilled in the art will appreciate that the present invention can have applications in many other welding power supplies. Power supplies for MIG welding can operate using a short circuit transfer technique, a pulse jet transfer technique or a continuous jet transfer technique. In the short circuit transfer, fill wire is automatically fed from the power supply to the welding place. Welding current is applied to the filler wire, which generates a welding arc between the filler wire, which acts as an electrode, and a workpiece. As the operator passes the electrode over the work piece at the welding location, the filler wire creates a short circuit with the work piece, releases a drop of filler wire into it, thereby opening the circuit and, Subsequently, the filler wire is advanced to create another short circuit. Accordingly, the filler wire and the workpiece produce a series of short circuit contacts as filler wire is applied to the workpiece. A disadvantage of the short circuit welding process on aluminum material is that the weld is porous (ie, has a poor diffusion quality). In steel, short circuit welding works well and is an accepted conventional method, although it should not be used in aluminum material because of the lack of fusion of the weld. In addition, the porosity of transfer welding with short circuit in aluminum produces a weaker weld. During short circuit welding, the arc produces a characteristic audible "effervescence" sound. In the technique of jet welding with pulse jets, the filler wire does not create a short circuit with the work piece. This is achieved because the welding device creates a welding current in pulses, including a first low welding current and a second high welding current (and possibly additional current levels). Since the pulse jet operates at these different current levels, the filler wire creates a weld deposit that is allowed to cool slightly between pulse and pulse. In addition, the average current is kept lower than that required for a continuous stream, while the maximum pulse amperage is large enough to create an axially stable arc. These characteristics allow a better control in the welding of thin metals. Preferably, when at least one of the first welding current falls and the second high welding current is applied above a transition current of the filling wire. The transition current of the filler wire is the current at which the welding arc provides a sufficient magnetic field to direct the molten filler wire in the direction of the workpiece. This creates an axially stable welding arc, since the magnetic field of the arc is able to direct molten filler wire in all positions on the workpiece, including positions that can only be reached against the direction of gravity. Continuous jet welding does not require a pulse welding current, but it occurs at higher currents than in the short circuit transfer technique. Many low cost MIG welding power supplies allow only short circuit transfers or continuous jet transfers. Most energizing supplies, which allow jet transfer in pulses are significantly more expensive (ie, power supplies with rectifier), partly because these power supplies also allow operator control over the various characteristics of the pulse. welding (for example, pulse length, pulse frequency, pulse amplitude, etc.). Accordingly, the prior art does not disclose a soldering device capable of pulse jet transfer to achieve high quality welding at low welding current in a low cost and easy to use soldering device. Recently, the Aluminum Association promoted the pulse welding method for aluminum; however, an adequate, low-cost, easy-to-use pulse jet welding power supply is not available. Since the Aluminum Association supports pulse jet welding to weld aluminum and other low-caliber metals, it is quite possible that less experienced welders have the need for a suitable, low-cost soldering device. Presently available pulse jet devices contain a plurality of adjustment handles, which allow an inexperienced operator to select jet welding conditions in invalid or undesirable pulses. These operators are accustomed to adjusting the voltage and wire feed speed in short circuit or continuous jet power supplies, but are less familiar with the plurality of parameters required for a suitable pulse jet welding. Accordingly, a pulse jet device having simplified operator interface controls suitable for types of filler wire commonly used in common soldering applications in aluminum and other thin metals is necessary. In addition, a welding power supply having short circuit transfer, pulse jet transfer and continuous jet transfer capabilities is required to allow the operator to utilize the advantages of continuous jet transfer (for example, for applications such as welding of aluminum or steel where the thickness of aluminum or steel is large), pulse jet transfer for thinner materials, and short circuit transfer for thinner steel materials. This system would be low cost and easy to operate. SUMMARY OF THE I VENTION These and other limitations of the prior art were solved with the present invention which, according to one embodiment, is a welding machine with arc to supply a continuous feeding electrode to a welding place. The machine includes a line frequency transformer that has a primary coil, a first secondary coil and a second secondary coil. The first secondary coil supplies a welding energy with a first voltage at a welding power output terminal. The second secondary coil supplies a second welding energy possessing a second, higher voltage, at an input terminal of a switch. The switch is controlled to supply pulsed energy at the welding power output terminal. In accordance with another exemplary embodiment, an arc welding machine is disclosed to supply a continuous feed electrode to a welding location. The machine includes a line frequency transformer device, including first and second secondary coils, for receiving a line frequency energy and for supplying first and second welding energies. The second welding energy has a higher voltage than the first welding energy. The machine includes a first device for receiving the first welding energy and for supplying a background welding energy at the welding energy output. The machine also includes a second device for receiving the second welding energy to supply a pulse welding energy at the output terminal of the welding energy. In accordance with another exemplary embodiment of the present invention, an arc welding machine is disclosed for supplying a continuous supply of electrode to a welding location. The machine includes an energy circuit for supplying pulse welding energy to the welding location having a fixed frequency and a fixed pulse length, where the fixed frequency and the fixed pulse length are essentially free of operator adjustments. According to one more characteristic of this mode, the energy circuit also supplies the welding energy in pulses with a maximum current that is essentially fixed. In accordance with another exemplary embodiment of the present invention, an arc welding machine is disclosed to provide a continuous feed of filler wire to a welding location. The machine includes a single-phase AC power source, a rectifier circuit and a switch. The AC power source supplies an energy signal. The rectifier circuit is coupled to the AC power source and essentially rectifies the energy signal. The AC power source supplies the rectified energy signal to the welding location with a constant voltage characteristic. The switch is coupled to the AC power source and supplies a pulsed energy signal with a constant current characteristic to the welding location. According to a further exemplary embodiment of the present invention, an energy circuit is disclosed for supplying pulsed welding capability to a welding power supply. The welding power supply is of the type that has a line frequency transformer to supply a first welding energy at a welding power output terminal. The power circuit includes a transformer, a switch and a control circuit - The transformer supplies a second welding energy. The switch is coupled with the transformer to receive the second welding energy. The control circuit is coupled with the switch and controls the switch to supply a pulse welding energy at the welding power output terminal. The pulse welding energy has a fixed frequency, a fixed maximum current and a fixed pulse length. The fixed frequency, the fixed maximum current and the fixed pulse length are essentially free of operator adjustment. According to yet another exemplary embodiment of the present invention, an energy circuit for an arc welding machine is disclosed for supplying a pulse welding arc based on a line frequency energy. The energy circuit includes a first energy circuit for supplying a welding master energy to a welding location. The power circuit further includes a second power circuit for supplying to the welding location a pulse welding energy having a fixed pulse length. The second power circuit includes a control circuit for adjusting the pulse length based on line frequency energy to provide a pulse having an essentially constant current. BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be more fully understood from the following detailed description, taken in conjunction with the accompanying drawings, where similar reference numerals refer to similar parts, and where: Figure 1 is a perspective view of an electric arc welder having simplified controls for the operator, in accordance with an exemplary embodiment of the present invention. Figure 2 is a circuit for selectively supplying welding current in a pulse jet welding technique or a short circuit welding technique, in accordance with an exemplary embodiment of the present invention. Figure 3 is a waveform diagram showing voltage and current characteristics at various points in the circuit of Figure 2. Figure 4 is a circuit diagram showing an alternative embodiment of the switch of Figure 2. Figure 5 is a circuit diagram showing another alternative embodiment of the switch of Figure 2. Figure 6 is a circuit diagram showing an alternative for the circuit of Figure 2. Figures 7A to 7F are waveform diagrams that show the output current and the output voltage for several parameters of a multiple tap transformer in accordance with the mode shown in Figure 2. Figure 8 is a schematic diagram of a control circuit for the circuit of Figure 2, in accordance with an exemplary embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to Figure 1, an electric arc welder 10 is shown in accordance with an exemplary embodiment of the present invention. The arc welder 10 is a MIG welding device, but alternatively other welding devices can be.

The welder 10 includes an applicator 12 and an applicator with coil 13, each for supplying consumable electrodes 14 and 15 and a protective gas (the source is not shown) to a welding place. Since the arc welder 10 is a wire feed power supply, a wire feeder mechanism and a fill wire supply (not shown) are housed in the arc welder 10 for welding with steel filler wire using the applicator 12. For welding with aluminum filler wire using the coil applicator 12, a coil of filler wire and a wire feeder mechanism are provided on the coil applicator 13. The applicator with coil 13 is coupled with the coil 13. welder 10 in the support 14, and receives welding energy from it. During MIG welding, the arc welder 10 controls the speed at which filler wire is supplied to a welding location. The consumable electrode 14 is an aluminum wire with a diameter of 0.89 millimeters. Alternatively, fill wires of 0.76, 0.58, or more or less than filler wire of 0.89 millimeters may be used. The electrode 14 may alternatively be of any other composition suitable for welding (for example, aluminum alloy, steel or steel alloy, siliceous bronze, aluminum bronze or other metals). The protection gas can be pure argon gas for welding aluminum, carbon dioxide or mixed gas of carbon dioxide and argon for welding steel, or any other protective gas or protective gas mixture suitable for welding aluminum or steel. The arc welder 10 further includes a work clamp 16 adapted to produce the electrical connection with a work piece for the arc welder 10. According to one embodiment, the arc welder 10 may include a work clamp support for the arc welder 10. electrically coupling the work clamp 16, an output support for pulse welding for pulse welding with an aluminum welding applicator and an output support for welding steel with short circuit welding with a second welding applicator with steel. In this embodiment, both applicators can be coupled simultaneously with the arc welder 10, while gas and welding energy are only supplied to the applicator selected by the operator. The arc welder 10 includes a simple series of operator controls 18, including a pulse on / off switch 20, a voltage selector 22 and a wire feed speed selector 24. Naturally, a power selector is also provided. On and off of the welder 21. The on-off switch 20 allows the operator to switch between a pulse jet transfer technique and a short circuit transfer technique. The voltage selector 22 allows the operator to select from a range of welding voltages suitable for a range of workpieces. According to one embodiment of the present invention, the voltage selector 22 has five positions that vary from a first low voltage parameter to a fifth high voltage parameter. In an alternative embodiment, the selector 22 may select from a continuous range of voltages, from the low voltage parameter to the high voltage parameter. The wire feed speed selector 24 allows the operator to select a wire feed speed, which determines the speed with which consumable electrode 14 is supplied to a welding location. According to an advantageous feature of the present invention, the operator controls 18 are few (ie, approximately three), and do not allow the operator to have essential control over the characteristics of the pulse (ie, frequency, maximum amplitude, pulse length, etc.) in the pulse jet transfer technique. Accordingly, the pulse frequency, maximum amplitude, pulse length and other pulse characteristics are fixed. Therefore, these controls are adapted for operators with less experience in welding, but also for those who have more experience in welding. The arc welder 10 advantageously provides a pulse welding current in a pulse jet transfer technique having characteristics suitable for relatively low current welding applications. Referring now to Figure 2, a power supply circuit 50 according to an exemplary embodiment of the present invention will be described. The power supply circuit 50 includes a transformer 52, a rectifier circuit 54, a capacitor 56, an inductor 58, a diode 60 and a controlled switch 62. The transformer 52 includes a primary coil 64 for receiving a line frequency energy , a first secondary coil 66 and a second secondary coil 68. The first secondary coil 66 supplies a first voltage to a line 72. In this embodiment, the first secondary coil 66 includes a plurality of branches 70 (ie, a tap transformer). multiple) numbered 1 to 5 to provide one of a plurality of welding power outputs to the line 72 at a plurality of respective voltages. The second secondary coil 68 supplies a second welding energy having a second voltage higher than the first voltage. In this embodiment, the second secondary coil 68 is an extension coil, although alternatively it can be a separate coil or another source. An extension coil is a coil coupled with the first secondary coil 66, while a separate coil is a coil that derives energy from the first coil 64 and is not directly coupled with the first secondary coil 66. In a preferred embodiment, the second secondary coil 68 is an extension coil with wire of smaller caliber than that of the first secondary coil 66. The line 72 feeds a welding energy to a rectifier circuit 54 which is a full-wave bridge rectifier, but alternatively it can be treated of other types of rectifier circuits (for example, half-wave rectifiers, diodes, etc.). The rectifier 54 is coupled to the capacitor 56, which is an electrolytic capacitor, but alternatively it can be another type of capacitor. A capacitor terminal 56 functions as a welding work terminal 74, which is coupled with the clamp 16. The other capacitor terminal 56 is coupled in series, via the inductor 58 and the diode 60, with the power terminal of the capacitor 56. welding 76, which supplies power to the electrode 14. The controlled switch 62 includes a control circuit 78 and a switch 80. The control circuit can be a microprocessor (e.g., a microprocessor or microcontroller Motorola or Intel) or control circuit discrete components for supplying a control signal to the switch 80 through the line 82. The switch 80 is preferably a silicon controlled rectifier (SCR), but alternatively it can be an isolated port bipolar transistor (IGBT) or other switching device . The control circuit 78 receives control signals from the simple controls for the operator 18. In response to a pulse signal from the on / off switch of the on / off pulse selector 20, the control circuit 78 selectively supplies the signal of control to the switch 80 by the line 82. The wire feed speed selector 24 supplies a wire speed signal to the control circuit 78 or a second control circuit that controls the speed at which the consumable electrode is fed. 14 to the welding place. The voltage selector 22 is coupled with a switch 84 to control which of the leads 70 is coupled with the line 72, thereby controlling the magnitude of the voltage that is applied to the consumable electrode 14. In operation, the power supply circuit 50 generates a master welding energy and a pulse welding energy at the welding power terminal 76. For aluminum pieces with an approximate thickness of up to 3 millimeters, a pulse jet welding technique is preferable. For weld thicknesses of approximately 10 millimeters or more of aluminum, and for steel, a continuous jet welding technique is preferable. The power supply circuit 50 supplies a single phase welding energy with a relatively low current (ie, an average current of approximately 225 Amps) in the following manner. A line frequency energy enters the circuit through the primary coil 64. The first secondary coil 66 is part of a multi-tap transformer. Notably, the power supply circuit 50 includes a single transformer for the master welding energy and the pulse welding energy, thereby greatly reducing the cost of installing multiple transformers (that is, one for the master welding energy, and one for the pulse welding energy). The addition of extension coil 68 and the elimination of a second transformer contribute together for this significant reduction in cost. The operator sets the switch 84 to select one of the leads 70 to supply the line 72 with a master welding energy having a first voltage. The rectifier 54 receives this master welding energy, rectifies the master welding energy and supplies it to a capacitor 56. Accordingly, in an exemplary embodiment, the capacitor 56 includes four electrolytic capacitors of 30,000 micro Farad (μF) in parallel (one total of 120,000 μF) adjusted to 50 VDC at 85 degrees Celsius. A gentle wave of master welding energy is supplied to the inductor 58 which, in one embodiment, is a Stabilizer Zl output inductor manufactured by Miller Electric Mfg. Co. adjusted to 150A, 23V and 60% yield. The inductor 58 absorbs the welding master energy and supplies it through the diode 60 to the welding power terminal. The diode 60 functions to prevent the current flow of the switch 80 from returning to the capacitor 56. A second welding energy is supplied by the second secondary coil 68 at a voltage greater than that of the first welding energy. The pulse welding energy is interrupted via the switch 80 by the control circuit 78 at a predetermined frequency. In one embodiment, the control circuit 78 pulses to the switch 80 at an essentially fixed frequency which is a multiple of the line frequency, which may be approximately half the line frequency (eg, 30 Hertz for a frequency of 60 Hertz line, 25 Hertz for a line frequency of 50 Hertz, etc.) and supplies a pulse with an essentially fixed pulse length of approximately 1.75 milliseconds, using approximately 20% of the positive half cycle of the high voltage waveform which is received from the second secondary coil 68 (see Figure 3 and the following discussion). The predetermined frequency can be a minimum of 24 Hertz, in which case the intermittency of the pulse is annoying for the operator, or of a maximum of 50 Hertz or more, and above this maximum the current of the welding energy is made too high for most welding operations with low current. For a consumable aluminum electrode with a diameter of 0.9 millimeters, a pulse length of approximately 1.75 milliseconds and a pulse welding current with a maximum current of 250 Amperes is considered suitable for low current aluminum welding applications. the master welding energy. The fixed pulse length of 1.75 milliseconds, the maximum amperage of fixed pulses (for a given load) and a fixed frequency makes its operation easy for operators with less experience and the adaptability of the supply to specific welding applications. The optimum pulse length is partly determined based on the impedance of the transformer. The optimal maximum pulse current is based in part on the transition current of the filler wire and is selected as somewhat greater than this transition current, in order to an exemplary embodiment. The master or background welding energy has a mean current less than the transition current of the filler wire, since the short circuit welding transfer typically welds below this transition current. Other factors can affect the optimal pulse length and the optimal maximum current. For example, the composition of the shielding gas can affect the transition current. If this factor is significant, the maximum pulse current must be set to ensure that the maximum current is greater than the transition current despite the effect of various protective gas compositions. further, the voltage of the line frequency energy can vary from one place to another, for example, between 205 and 225 volts. This variation can significantly affect the maximum current during pulse welding. Accordingly, according to an advantageous feature of the present invention, FIG. 8 reveals a mode of the control circuit 78 having an improved characteristic in which the pulse length of the pulse welding energy is automatically adjusted based on the variation of the line frequency voltage to accommodate variations in the pulse current. As will be understood by the expert of the technique, this function can be performed by various circuit modalities. According to this exemplary embodiment, the control circuit 78 receives a line frequency energy Ll in a transformer 150 having a first terminal 152, a second terminal 154 and a central branch 156. A rectifier 159 is coupled with the terminals first and second 152 and 154 for supplying unregulated and rectified power (DC) to lines 158 and 160. In this exemplary embodiment, line 158 supplies 22.5 volts DV (VDC) positive and line 160 supplies 22.5 VDC negative. A voltage regulator circuit 162 is coupled with lines 158 and 160 to supply regulated power of, for example, +15 VDC and -15 VDC to terminals 164 and 166, respectively. An AC voltage waveform of the second terminal 154 is multiplied by the resistors 168 and 170 and is supplied to an operational amplifier (op amp) 172. The op amp 172 supplies a square wave output with a pulse length of approximately 8.3 milliseconds (i.e., half the frequency of 60 Hertz of the AC voltage waveform) to the op amp 174. The op amp 174 supplies a sawtooth output waveform to a first terminal 176 of a comparator 178. A DC command signal is supplied to a second terminal 180 of comparator 178. When the sawtooth signal exceeds the DC command signal, a current pulse is initiated when transmitting a signal through digital logic 182. to a switch initiating circuit 184. When the sawtooth signal falls below the DC command signal, the current pulse ends. In summary, the pulse length of the current pulse supplied by the switch 80 is determined by the points at which the sawtooth signal crosses the command signal DC. Therefore, if the voltage of line frequency energy L! increases, the pulse length increases; if the voltage of the line frequency energy Ll decreases, the pulse length also decreases. Accordingly, the present invention supplies a DC command signal that is dependent on the line frequency energy. The DC voltage not regulated and supplied on line 160 is multiplied through resistors 186, 188 and 190 to a first terminal of op amp 192. Since this voltage is not regulated, it will increase or decrease based on the frequency energy. line Exemplary values for resistors 186, 188 and 190 include two kiloohms (KO) for resistor 186, an O for resistor 188 and 162 KO for resistor 190. Op amp 192 supplies the unregulated command signal to the second terminal 180 of comparator 178. In operation, when the voltage of the line frequency increases, the pulse length decreases, and when the line frequency voltage decreases, the pulse length increases, where both operations act to maintain a current of constant pulse welding supplied by switch 80. As an additional refinement, the DC command signal may be "twisted" or slightly adjusted for welding power supplies with different applications. A potentiometer 194 has a power terminal coupled to one of the terminals of the voltage regulator, for example terminal 166. A DC voltage based on the parameters of potentiometer 188 is supplied to op amp 162 through resistor 196. Exemplary values for potentiometer 194 and resistor 196 include a KO for potentiometer 194 and 619 KO for resistor 196. During manufacture, potentiometer 194 can be set to a desired fixed pulse for a particular welding operation, the thickness of the wire of filling, etc. Accordingly, the fixed pulse length is automatically adjusted based on the line frequency voltage, but is not adjustable based on operator inputs. Referring now to Figure 3, waveforms are shown for a single line frequency energy cycle at various points in the power supply circuit 50. Va is the high voltage waveform derived from the second secondary transformer 68. The waveform indicates in a shaded portion the portion of the waveform passing through the switch 80 when the switch 80 is initiated by the control circuit 78. This portion is equivalent to approximately 1.75 milliseconds in pulse duration (it is say, about 2% of the positive half cycle of the waveform), but it can also be between 1.7 and 1.9 milliseconds in accordance with a low current mode of the present invention. Vb indicates the low voltage waveform derived from the first secondary coil 66. Ic represents the master welding energy in DC form rectified by the rectifier 54, smoothed by the capacitor 56 and damped by the inductor 58. Ic may alternatively have certain degree of oscillations based on the selection of the capacitor 56 and the inductor 58. Id represents a single pulse of pulse welding energy. Finally, it represents a single cycle of welding energy, including pulse welding energy and master welding energy, at the welding power terminal 76. As previously mentioned, the control circuit 78 causes the switch 80 to be pressed approximately 30 Hertz. This frequency provides a simple and inexpensive pulse, since it is a multiple of the input line frequency energy, and also supplies welding energy in pulses of low current with respect to time in relation to higher frequencies, such as or 120 Hertz. Advantageously, the SCR, diode 60, extension coil 68 and control circuit 78 are low cost elements to further contribute to the simplicity and economic nature of the present invention. In an alternative embodiment, a switch 93 comprises a capacitor 90 coupled with an insulated port bipolar transistor (IGBT) 92 as shown in Figure 4. A power input signal is applied to an input terminal 94 from a second secondary coil 68 (see Figure 2) which may be an extension coilA separate coil or higher branch in the first secondary coil 66. The energy input signal could alternatively be supplied by a second transformer, a voltage doubler (ie, the voltage duplicator shown in Figure 6) , or another source of energy, although the modality that includes a second transformer can add an element of undesirable cost. In this embodiment, IGBT 92"boots" the capacitor 90 in response to charge accumulation or in response to an input as a control input from the control circuit 78 to create the high voltage pulse. The combination of IGBT 92 and capacitor 90 could be controlled at any frequency, ie, not only a multiple of the line frequency. However, the configurations of this modality could be more expensive than the simple version explained above. Another alternative embodiment of the switch 80 is shown in Figure 5. In this embodiment, a switch 95 includes a first SCR 96 and a second SCR 98, both controlled by the control circuit 78. An AC 100 source, which in this embodiment is shown as a coil, it supplies a first half power cycle to the first SCR 96 during which the control circuit 78 initiates the first SCR 96 at a multiple of the line frequency, and supplies a second half cycle of power to a second SCR 98 during which the control circuit 78 initiates the second SCR 98 at the same multiple of line frequency. With each SCR 96 and 98 starting, for example, half the line frequency (ie, 30 hertz or 25 hertz), the pulsed energy signal is supplied to terminal 102 at the line frequency (i.e., 60 Hertz or 50 Hertz). Naturally, other configurations and start frequencies are contemplated. The source AC 100 can be an extension coil, a separate coil, a higher branch of the first secondary coil 66, a second transformer or another source AC. Yet another embodiment of the present invention is disclosed in Figure 6. In this embodiment, the rectifier circuit 54 and the controlled switch 62 are combined in a circuit 106. The circuit 106 includes an AC source, which in this case comprises a power transformer. central branch 104 having a work terminal 105 and a voltage doubler 108. Rectifying diodes 110 and 112 rectify the full wave of the line frequency energy signal from the AC source and supply the rectified signal as a master power signal in terminal 114 (capacitor 56, inductor 58 and diode 60 are described with reference to Figure 2). The switches 116 and 118 are controlled by the control circuit 78 to transmit current in response to the control signals from the control circuit 78. The voltage duplicator 108 comprises a first diode 120 coupled at its anode with the first terminal of the AC source, and at its cathode with the positive terminal of a first capacitor 122 (ie, an electrolytic capacitor). The capacitor 122 is coupled in its negative terminal with the second terminal of the AC source. The switch 118 couples the cathode of the diode 120 with the terminal 114. In similar but opposite configurations, a second diode 124 is coupled at its anode with the second terminal of the AC source and at its cathode with the positive terminal of a second capacitor 126. (that is, an electrolytic capacitor). The capacitor 126 is coupled in its negative terminal with the first terminal of the AC source. The switch 116 couples the cathode of the diode 124 with the terminal 114. In operation, the voltage doubler 108 stores a charge that can be subsequently discharged by the operation of the switches 116 and 118. During the positive half cycle of the line frequency energy in the AC source, the diode 120 reverses its polarity and does not conduct current, while the diode 124 acquires direct polarization and conducts current to the charging capacitor 126 so that the voltage across the capacitor 126 is approximately equal to the maximum voltage of the capacitor. Line frequency power (ie, 60 volts). The switches 116 and 118 remain off when controlled by the control circuit 78. The rectifier 110 conducts current to supply the first half cycle of the welding master power, which is subsequently smoothed and conditioned by the capacitor 56 and the inductor 58. During the negative half cycle of the line frequency energy in the AC source, the diode 120 acquires direct polarization and conducts current to the charging capacitor 122, so that the voltage across the capacitor 122 is approximately equal to the maximum voltage of the line frequency energy . Further, during the negative half cycle, a first voltage on the negative side of the capacitor 126 is high relative to the common 105, supplying a voltage on the positive terminal of the capacitor 126 equal to the negative voltage plus the master welding voltage previously stored in the capacitor 126 In this way a higher voltage than the master welding voltage is achieved. In addition, during the negative half cycle of the line frequency energy at the AC source, the rectifier 112 conducts current to supply the second half cycle of the welding master power, which is subsequently smoothed and conditioned by the capacitor 56 and the inductor 58 (see Figure 2). Subsequent to this charge accumulation step, control circuit 78 initiates switch 118 to discharge capacitor 122. During the next half cycle, the control circuit 78 initiates the switch 116 to discharge the capacitor 126. Accordingly, the control circuit 78 initiates the switches 116 and 118 to supply a pulse at a fixed frequency, i.e., the line frequency. Alternatively, diode 120, capacitor 122 and switch 118 could be eliminated to provide a pulse at half the line frequency. The control circuit 78 may also initiate the switch 116 or switches 116 and 118 to other frequencies. The control circuit 78 preferably initiates the switches 116 and 118 to a fixed pulse length (i.e., 1.7 milliseconds). While the DC current of the pulse welding energy in the various embodiments may be one of a variety of amperages, this DC current is preferably higher than the transition current of the fill wire comprising the electrode 1. Several factors affect the transition current. These include the diameter of the electrode, the chemistry (alloy) of the electrode and the "lift" of the electrode. The "lift" of the electrode refers to the distance that the electrode 14 extends from the nozzle of the applicator 12. For example, the transition current of an aluminum wire of 0.9 millimeters with an elevation of 6 millimeters is approximately 200 to 205 amperes. Accordingly, supplying a pulse with a maximum amperage of 250 amperes is sufficient to exceed the wire transition current of 0.9 millimeters, thereby creating an axially stable arc. Preferably, the pulse welding energy has a maximum amperage of 250 amps in one embodiment of the present invention. However, other configurations are contemplated for welding applications of various amperages, types and sizes of workpieces, etc. The pulse length of 1.75 milliseconds is selected to preferably remove a counting of molten filler wire at a time from the consumable electrode 14. If the pulse length is too narrow for the filler wire no counting will occur, but if the pulse length It is very wide, more than one account will fall. Neither of these situations is a desirable feature for pulse jet welding. Referring now to Figures 7A to 7F, waveform diagrams are shown for various parameters of the voltage selector 22. In this embodiment, the circuit 50 is configured as shown in Figure 2, ie, the transformer 52 is a multi-tap transformer to allow the operator to select, via voltage selector 22, a desired voltage by adjusting the leads 70 that are desired to be coupled to line 72. The multi-tap transformer can be replaced by other switch configurations, diodes , etc., to perform the same function. In Figure 7A, the waveforms were taken when welding with aluminum 4043 of 0.9 millimeters in diameter on a piece of aluminum with a thickness of 1 millimeter. Ii represents the pulse welding energy when the switch 84 is fixed with the branch 1 of the plurality of branches 70. X1 includes a pulse welding energy component 88 that pulses at a frequency of approximately 30 hertz and has an amperage maximum, when combined with the welding master component 86 of about 280 amperes. The corresponding voltage waveform has a DC component of approximately 16 volts DC and a maximum voltage of approximately 25 volts DC at the same frequency of the pulse welding energy component 88. In Figure 7B, the waveforms were taken when welding with aluminum 4043 of 0.9 millimeters in diameter on a piece of aluminum with a thickness of 2 millimeters. I2 represents the pulse welding energy when the switch 84 is fixed with the branch 2 of the plurality of branches 70. When the operator manipulates the voltage selector 22 to adjust the switch 84 with the second branch, the resulting waveform is I2. This increases the arc length of the resulting weld arc, which the operator recognizes as an undesirable situation. Accordingly, the operator manipulates the wire feed speed selector 24 to increase the wire feed speed, which decreases the arc length and increases the welding current primarily as the welding master current increases, and not the current of the wire. pulse welding. I2 includes a welding power master component 86 at approximately 60 DC amperes and a pulse welding power component 88 that pulses at a frequency of approximately 30 hertz and with a maximum amperage, when combined with the welding master component 86 of about 300 amps. The corresponding voltage waveform has a DC component of about 17 volts DC and a maximum voltage of about 25 volts DC at the same frequency as the pulsed welding energy component 88. Simultaneously, Figures 7C to 7F show forms of wave for similar increases in wire feed voltage and speed. In Figure 7C, the waveforms were taken when welding with aluminum 4043 of 0.9 millimeters in diameter on a piece of aluminum with a thickness of 3 millimeters. The welding energy has a background current of about 80 ADC, a maximum pulse of about 320 ADC, a voltage of about 18 VDC and a maximum voltage of about 27 VDC. In addition, the background current has a slight undulation. In Figure 7D, the waveforms were taken when welding with aluminum 4043 of 0.9 millimeters in diameter on a piece of aluminum with a thickness of 3.175 millimeters. The welding energy has a background current of approximately 90 ADC, a maximum pulse of approximately 320 ADC, a voltage of approximately 20 VDC and a maximum voltage of approximately 29 VDC. In Figure 7E, the waveforms were taken when welding with aluminum 4043 of 0.9 millimeters in diameter on a piece of aluminum with a thickness of 4.76 millimeters. The welding energy has a background current of approximately 130 ADC, a maximum pulse of approximately 350 ADC, a voltage of approximately 22 VDC and a maximum voltage of approximately 32 VDC. In Figure 7F, the waveforms were taken when welding with aluminum 4043 of 0.9 millimeters in diameter on a piece of aluminum with a thickness of 6.35 millimeters. The welding energy has a background current of approximately 150 ADC, a maximum pulse of approximately 360 ADC, a voltage of approximately 23 VDC and a maximum voltage of approximately 33 VDC. A feature disclosed in Figures 7A to 7F is that, even when the operator selects the pulse mode of operation, when voltage selector 22 is increased to leads 4, 5 or 6 (ie, Figures 7D to 7F) , the welding current makes a transition from a pulse mode to a continuous jet mode, as the operator is instructed to stop the pulse sound characteristic of pulse welding energy. Another feature of the present invention, in particular the embodiments of Figures 2 and 7A to 7F, is that the master welding energy has a constant voltage characteristic and the pulse welding energy has characteristics of constant voltage and constant current. Briefly, the characteristics of constant current ("CC") and constant voltage ("VC") describe how a supply of welding energy reacts in response to a change in the length of the arc. A constant welding current characteristic (also called "slanted") generally requires a voltage follower controller coupled with the wire feed mechanism. If the arc length increases, the controller increases the wire feed speed to reduce the arc. A constant voltage welding characteristic does not require a voltage follower controller because current increases in response to a decrease in arc length, which in turn increases the rate of fusion of the wire, subsequently causing the arc length to increase. In response to an increase in the length of the arc, the current decreases, decreasing the melting rate of the wire, subsequently causing the arc length to decrease. Reference is made to Welding Handbook, Volume 2: Welding Processes, Eighth Edition, pp. 3-4, 12-14 (American Welding Society 1991) for more definitions of the terms constant current and constant voltage. One aspect of the present invention is that the circuit supplying the pulse welding energy (i.e., switch 80) has both constant current and constant voltage characteristics, while the circuit supplying the master welding energy possesses a constant voltage characteristic. The constant voltage characteristic of the pulse welding energy is due to the fact that the switch 80 is directly coupled to the second secondary coil 68 of the transformer 52. The constant current characteristic of the pulse welding energy is due to the high impedance of the transformer 52. This impedance is the result of several factors in the exemplary embodiment of Figures 2 and 7A to 7F, including the small size of the transformer, which increases the leakage inductance, the small bore of the extension coil which increases the resistance, and the coupling coefficient of the second secondary coil 68 with the primary coil 64. Still in the alternative embodiment in which the gauge of the extension coil is not smaller than that of the first secondary coil 66, the transformer 52 it includes sufficient impedance to give the pulse welding energy a constant current characteristic. The constant current characteristic of the pulse welding energy can be seen in the waveforms of Figure 7, although an alternative embodiment of the circuit of Figure 2, in which the pulse welding energy was only constant voltage could be configured to produce waveforms similar to those of Figure 7. Accordingly, it can be appreciated that it is possible to provide a supply of welding power that allows pulse jet welding in addition to short circuit welding in MIG welding machines, while that the overall costs are reduced significantly by using simple and inexpensive components, and also the complexity for the operator of the energy supply is reduced. Never before has a pulsed system been available at this price range. Also, the arc welder of the present invention has advantages over higher energy supplies of 60 or 120 hertz, in the sense that a lower current can be supplied in a single and simpler power supply.

Additionally, a separate circuit is provided for adding pulsed jet welding, as opposed to some prior art devices that use complex and expensive circuits (i.e., multiple transformers) to integrate the pulse circuit with the power master circuit. While the modalities illustrated in the figures and described above are those currently preferred, it should be understood that these modalities are offered only by way of example. For example, as an alternative embodiment, the control circuit 78, the switch 80 and a transformer may be part of an added circuit for an existing MIG welding power supply to provide welding capability in pulses to the welding power supply. Many alternative embodiments of the present invention are contemplated based on the novel features of the device of the present invention. The present invention is not limited to a particular embodiment, but extends to several modifications that are nevertheless within the scope of the appended claims.

Claims (47)

1. CLAIMS 1. An arc welding machine for supplying a continuous feed electrode to a welding location comprising a line frequency transformer having a primary coil, a first secondary coil for supplying a welding energy with a first voltage at a welding power output terminal, and a second secondary coil for supplying a second welding power with a second higher voltage to an input terminal of a switch, where the switch is controlled to supply pulsed power to the terminal output of the welding energy.
2. 2. The arc welding machine of claim 1, wherein the switch supplies pulsed energy with a pulse duration of about 1.75 milliseconds.
3. 3. The arc welding machine of claim 1, wherein the second secondary coil is an extension coil.
4. 4. The arc welding machine of claim 3, wherein the extension coil has a wire of smaller caliber than that of the first secondary coil.
5. 5. The arc welding machine of claim 1, wherein the second secondary coil is a separate coil.
6. The arc welding machine of claim 1, wherein the combined welding energy and pulsed energy provide a jet welding energy suitable for welding aluminum with a thickness of about 3 millimeters or less.
7. The arc welding machine of claim 1, wherein the switch supplies a pulse energy with a fixed frequency of about 30 Hertz.
8. The arc welding machine of claim 1, further comprising a rectifier circuit and a capacitor coupled between the first secondary coil and the welding power output terminal.
9. The arc welding machine of claim 8, further comprising an inductor and a second switch coupled in series between the capacitor and the welding power output terminal, where the second switch prevents pulsed energy from entering the rectifier circuit.
10. 10. The arc welding machine of claim 1, wherein the second secondary coil is part of a multiple bypass transformer.
11. 11. An arc welding machine for supplying a continuous feed electrode to a welding location comprising: a line frequency transformer device including first and second secondary coils for receiving a line frequency energy and for supplying energies of first and second welding, where the second welding energy has a higher voltage than the first welding energy; a first device for receiving the first welding energy and for supplying background welding energy to the welding energy output; and a second device for receiving the second welding energy and for supplying a pulse welding energy at the welding power output terminal.
12. 12. The arc welding machine of claim 11, wherein the second secondary coil is an extension coil.
13. The arc welding machine of claim 12, wherein the extension coil has a wire of smaller caliber than that of the first secondary coil.
14. 14. The arc welding machine of claim 11, wherein the second secondary coil is a separate coil.
15. The arc welding machine of claim 11, wherein the first secondary coil extends from a first line to a first branch and the second secondary coil extends from the first line to a second branch.
16. 16. The arc welding machine of claim 11, wherein the first secondary coil includes a plurality of taps, wherein the first device that receives the first welding power from one of the plurality of taps is based on an input device of the operator.
17. 17. The arc welding machine of claim 11, where the second device supplies a pulse energy that has a fixed pulse frequency.
18. 18. The arc welding machine of claim 17, wherein the pulse frequency is a multiple of the line frequency.
19. 19. The arc welding machine of claim 11, wherein the second device supplies a pulse energy having a fixed pulse length.
20. 20. The arc welding machine of claim 19, wherein the fixed pulse length is about 1.75 milliseconds.
21. 21. An arc welding machine for supplying a continuous feed electrode to a welding location, comprising an energy circuit for supplying pulse welding energy to the welding location with a fixed frequency and a fixed pulse length, where the fixed frequency and the fixed pulse length are essentially free of operator settings.
22. 22. The arc welding machine of claim 21, wherein the pulse welding energy has a master welding current and a pulse welding current, which further comprises a bottom voltage selector and a feed speed selector. of wire, both coupled with the power circuit, the background voltage selector and the wire feed speed selector that provides the operator's adjustability of the welding current master component of the pulse welding energy.
23. The arc welding machine of claim 21, wherein the pulse welding energy has a master welding current and a pulse welding current, wherein the power circuit comprises a first transformer for supplying the master welding current and a second transformer for supplying the welding current in pulses.
24. 24. The arc welding machine of claim 21, wherein the power circuit comprises a central tap transformer.
25. 25. The arc welding machine of claim 24, wherein the power circuit comprises a voltage doubler coupled to the central bypass transformer and a rectifier circuit coupled to the central bypass transformer.
26. 26. The arc welding machine of claim 21, wherein the fixed frequency is about 30 Hertz.
27. 27. The arc welding machine of claim 21, wherein the fixed pulse is approximately 1.75 milliseconds.
28. 28. The arc welding machine of claim 21, wherein the power circuit adjusts the pulse length based on a line frequency energy supplied to the power circuit to supply a pulse having a constant current.
29. 29. An arc welding machine for supplying a continuous feed filler wire to a welding location, comprising: a single-phase AC power source for supplying an energy signal; a rectifier circuit coupled with the AC power source to essentially rectify the energy signal and to supply the rectified energy signal with a constant voltage characteristic to the welding location; and a switch coupled with the AC power source to - supplying a pulse energy signal with a constant current characteristic to the welding location.
30. 30. The arc welding machine of claim 29, wherein the pulse energy signal has a fixed frequency.
31. 31. The arc welding machine of claim 30, wherein the pulse energy signal has a frequency of about a multiple of the line frequency.
32. 32. The arc welding machine of claim 29, wherein the pulse energy signal has a fixed pulse length.
33. 33. The arc welding machine of claim 29, wherein the pulse energy signal has a maximum amperage greater than the amperage of the rectified energy signal.
34. 34. The arc welding machine of claim 29, wherein the AC power source includes a first secondary coil and a second secondary coil, wherein the second secondary coil has a wire of smaller caliber than that of the first secondary coil, where the rectifier circuit is coupled to the AC power source and the first secondary coil and the switch are coupled to the AC power source in the second secondary coil.
35. 35. The arc welding machine of claim 29, wherein the AC power source includes a multi-tap transformer for supplying an energy signal of one of a plurality of voltages, wherein the voltage is selected by an adjustable choke selector. the operator.
36. 36. An energy circuit for supplying a welding capability in pulses to a welding power supply, where the welding power supply is of the type that has a line frequency transformer to supply a first welding energy to a terminal of welding power output, wherein the power circuit comprises: a transformer for supplying a second welding energy; a switch coupled with the transformer to receive the second welding energy; and a control circuit coupled with the switch to control the switch, in order to supply a welding energy in pulses to the welding power output terminal, where the pulse welding energy has a fixed frequency and a length of Fixed pulse, where fixed frequency and fixed pulse length are essentially free from operator adjustments.
37. 37. The power circuit of claim 36, wherein the fixed frequency is about 30 Hertz and the fixed pulse length is about 1.75 milliseconds.
38. 38. The power circuit of claim 36, wherein the fixed frequency is a multiple of the line frequency.
39. 39. The power circuit of claim 36, wherein the pulse energy has a constant current characteristic.
40. 40. The power circuit of claim 36, wherein the second welding energy has a higher voltage than the first welding energy.
41. 41. The power circuit of claim 36, wherein the first welding energy and the combined pulse welding energy provide pulsed jet welding energy suitable for welding aluminum with a thickness of about 3 millimeters or less.
42. 42. The power circuit of claim 36, wherein the control circuit adjusts the pulse length based on a line frequency energy to supply a pulse having a constant current.
43. 43. An energy circuit for an arc welding machine for supplying a welding arc in pulses based on a line frequency energy, comprising: a first energy circuit for supplying a master welding energy to a welding spot; and a second power circuit for supplying a pulse welding energy having a pulse length fixed to a welding location, wherein the second power circuit includes a control circuit for adjusting the pulse length based on the energy of the pulse. line frequency to supply a pulse that has an essentially constant current.
44. 44. The energy circuit of the claim 43, where the control circuit adjusts the pulse length based on the voltage of the line frequency energy.
45. 45. The power circuit of claim 43, wherein the second power circuit supplies a pulse welding energy with a fixed frequency, wherein the fixed frequency and the fixed pulse length are essentially free of operator settings.
46. 46. The power circuit of claim 45, wherein the fixed frequency is about 30 Hertz and the fixed pulse length is about 1.75 milliseconds.
47. 47. The power circuit of claim 43, wherein the second power circuit includes a silica-controlled rectifier coupled with the control circuit.