(19)
(11)EP 2 109 514 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
29.07.2020 Bulletin 2020/31

(21)Application number: 08724834.0

(22)Date of filing:  24.01.2008
(51)International Patent Classification (IPC): 
B23K 28/00(2006.01)
B23K 11/26(2006.01)
(86)International application number:
PCT/US2008/001019
(87)International publication number:
WO 2008/091699 (31.07.2008 Gazette  2008/31)

(54)

CAPACITIVE DISCHARGE WELDING POWER SUPPLY AND CAPACITIVE DISCHARGE WELDER USING THE SAME

STROMVERSORGUNG FÜR KONDENSATORSCHWEISSEN UND KONDENSATORSCHWEISSMASCHINE DAMIT

ALIMENTATION POUR SOUDAGE À DÉCHARGE CAPACITIVE ET SOUDEUSE À DÉCHARGE CAPACITIVE L'UTILISANT


(84)Designated Contracting States:
AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MT NL NO PL PT RO SE SI SK TR

(30)Priority: 24.01.2007 US 897379 P

(43)Date of publication of application:
21.10.2009 Bulletin 2009/43

(73)Proprietor: AMADA MIYACHI AMERICA, INC.
Monrovia, CA 91016 (US)

(72)Inventors:
  • GUNNING, Kevin
    Monrovia, CA 91016 (US)
  • LEVY, Stanley
    Monrovia, CA 91016 (US)
  • HUMPHREY, Glen, Holt
    Monrovia, CA 91016 (US)

(74)Representative: Gulde & Partner 
Patent- und Rechtsanwaltskanzlei mbB Wallstraße 58/59
10179 Berlin
10179 Berlin (DE)


(56)References cited: : 
EP-A1- 0 835 713
JP-A- S6 192 789
US-A- 5 272 313
US-A1- 2005 253 165
JP-A- S5 997 782
JP-A- H09 285 137
US-A- 5 947 093
US-B1- 6 614 670
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description

    FIELD OF THE INVENTION



    [0001] The present invention relates to a capacitive discharge welding power supply, and more particularly, to a capacitive discharge welder using the capacitive discharge welding power supply.

    BACKGROUND OF THE INVENTION



    [0002] CD welders have been used in a variety of industries for many years. The traditional weld process was to charge a capacitor bank to a relatively high voltage (hundreds or even thousands of volts), then fully discharge the capacitor bank through the pulse transformer and into the part to be welded. For improved welding results, many controls offer dual pulse welding capabilities wherein this process is repeated twice for each part to be welded. The first pulse is typically done at a low energy to "condition" the parts to be welded. The second pulse is then done at a higher energy to complete the weld.

    [0003] CD welders have the advantage of an output that is independent of the local line voltage. The charging circuit charges the capacitor bank up to a user-programmed voltage. The energy delivered by the welder depends only upon the value of the capacitors and their voltage by the formula E= ½ CV2 where E is the energy, C is the capacitance, and V is the capacitor bank voltage. As the line voltage varies, the time to charge the capacitor bank may vary, but the overall energy delivered does not vary. This is an advantage when compared with AC type welders that draw their energy directly off the incoming line and are susceptible to output variation when the incoming voltage varies during the weld.

    [0004] One alternate weld process is known as arc welding. A welding power supply is used in arc welding to generate an electric arc between an electrode and the base material to melt the metals at the welding point. The arc welding process requires an ongoing electric current (either direct (DC) or alternating (AC) current) to maintain the arc for a substantial period of time. This contrasts with capacitor discharge welders, which are single-shot devices. It should be noted that in arc welding, the parts to be joined are heated by the electric arc, and not by the resistance of the parts to be joined as the current passes through them. In addition, the voltage required to strike and maintain this arc is typically much higher that for capacitor discharge welders. Striking an arc can require 80V or more, while capacitor discharge welding is done at 10V or less. These differences mean that although similar electronic components may be used in both types of welders, the details of how they are used differ significantly.

    [0005] Typical CD welders today use a type of Silicon Controlled Rectifier (SCR) to connect the capacitor bank to the pulse transformer. A characteristic of these switches is that they can be turned on with a control signal input, but that they cannot be turned off until the current through them goes to zero. In short, they are turned on, and stay on until the current reaches zero (as when the capacitor bank is nearly depleted).

    [0006] Prior art also includes CD welders that used thyristors (Gate Turn Off or GTO devices) to connect the capacitor bank to the pulse transformer. However, these devices are typically used in the same manner as the SCR described above.

    [0007] Japanese patent application JP S59 97782 A discloses an impulse welder including a transistor configured to switch on and off to intermittently control discharge from a capacitor.

    SUMMARY



    [0008] In an exemplary embodiment according to the present invention, a capacitive discharge (CD) welder is provided. The CD welder includes a charging circuit, a capacitor bank, an insulated gate bipolar transistor (IGBT), a pulse transformer, a controller and a secondary circuit. The charging circuit takes incoming electricity and charges a capacitor bank. The capacitor bank stores energy. The IGBT electrically connects and disconnects the capacitor bank to the pulse transformer. The pulse transformer reduces voltage from that stored in the capacitor bank to the desired welding voltage. The controller is adapted to output a control signal to turn the IGBT on and off. The secondary circuit electrically connected to the pulse transformer provides a welding current corresponding to the output having the second voltage of the pulse transformer to a part to be welded, wherein an energy delivered by the secondary circuit depends only upon the value of the capacitor bank and the first voltage according to the formula E= ½ CV2 where E is the energy supplied, C is the capacitance of the capacitor bank, and V is the first voltage stored in the capacitor bank. The controller is adapted to turn off the IGBT at a point shortly after primary current supplied to a primary side of the pulse transformer increases while secondary current supplied by a secondary side of the pulse transformer does not increase.

    [0009] In one exemplary embodiment, the current is turned off early to avoid transformer saturation and overheating.

    [0010] In another exemplary embodiment, the current is turned on and off quickly multiple times at the start to reduce the rate of rise of the current.

    [0011] In another exemplary embodiment, the current is turned on and off quickly once to generate a short pulse with high peak current.

    [0012] In another exemplary embodiment, a method of welding a part using a capacitive discharge welder including a pulse transformer, is provided. The method includes: applying a current to the part; and turning off the current prior to a saturation of the pulse transformer.

    BRIEF DESCRIPTION OF THE DRAWINGS



    [0013] These and/or other aspects and features of various embodiments of the invention will become apparent and more readily appreciated from the following description of examples of embodiments, taken in conjunction with the accompanying drawings described below.

    FIG. 1 is a schematic diagram of a conventional capacitive discharge welder.

    FIG. 2 is a schematic diagram of a capacitive discharge welder in an exemplary embodiment according to the present invention.

    FIG. 3 is block diagram of a capacitive discharge welder in an exemplary embodiment according to the present invention.

    FIG. 4 is a plot of waveforms, in which the top waveform (i.e., secondary waveform) shows the secondary current of a CD welder fired through a large fixed load, and the bottom waveform (i.e., primary waveform) shows the current in the primary side of the CD welder.

    FIG. 5 is a plot of waveforms, in which the top waveform (i.e., secondary waveform) shows the secondary current and the bottom waveform (i.e., primary waveform) shows the current in the primary side of the CD welder. The primary current is shut off by the IGBT shortly after the primary current starts to increase again.

    FIG. 6 is a plot of a waveform of a weld pulse without rapid switching to reduce the rate of rise of current.

    FIG. 7 is a plot of a waveform of a weld pulse with rapid switching to reduce the rate of rise of current.

    FIG. 8 is a plot of a waveform of a short duration rapid rise weld pulse.


    DETAILED DESCRIPTION



    [0014] In an exemplary embodiment according to the present invention, a circuit is used to prevent saturation in a pulse transformer of a capacitive discharge welder. In this embodiment, the current to the primary coil of the pulse transformer is turned off early to avoid transformer saturation and overheating. In another exemplary embodiment the current to the primary coil of the pulse transformer is turned on and off (e.g., multiple times) quickly at the start to reduce the rate of rise of the current. In yet another exemplary embodiment, the current to the primary coil of the pulse transformer is turned on and off quickly once to generate a short pulse with high peak current.

    [0015] In other embodiments, the capacitive discharge welder may have one, more than one, or all of the features of the above embodiments.

    [0016] As can be seen in the schematic circuit diagram of FIG. 1, a conventional capacitive discharge (CD) welder 100 includes a power source (battery) 101, coupled to a capacitor 103 via a resistor 101. An SCR 104 and a primary coil 105a (primary side or input side) of the pulse transformer are coupled in series across the capacitor 103. A secondary coil 105b (secondary side or output side) of the pulse transformer is coupled to weld electrodes 106 for applying the output of the pulse transformer to materials or parts to be welded. In one embodiment, the ratio of windings between the primary and secondary coils is 30:1, however, the present invention is not limited thereto.

    [0017] In FIG. 1 (and in FIG. 2 below), a power input (e.g., AC input) is represented by a battery and a charging circuit is represented as a resistor, for example.

    [0018] As can be seen in the schematic circuit diagram of FIG. 2, a capacitive discharge (CD) welder 200 in an exemplary embodiment according to the present invention, includes a power source (battery) 202, coupled to a capacitor 203 via a resistor 201. An insulated gate bipolar transistor (IGBT) 204 and a primary coil (primary side or input side) 205a of the pulse transformer are coupled in series across the capacitor 203. A secondary coil 205b (secondary side or output side) of the pulse transformer is coupled to weld electrodes 206 for applying the output of the pulse transformer to materials or parts to be welded.

    [0019] One known issue with CD welders is that the pulse transformers can reach their saturation points. When the transformer saturates, increased current input to the primary side will merely result in losses within the transformer (which generates waste heat) and not produce additional secondary output. Traditional CD welder designs have had to allow for this possibility and design in additional cooling to account for it.

    [0020] In one embodiment, to avoid transformer saturation, the IGBT 204 is turned off after a delay, which may be programmed by the user. The delay may be provided, for example, by programming a controller (see FIG. 3) for turning the IGBT off and on. The cut off of the primary current has a very little effect on the waveform of the secondary current. Also, short, low energy pulses can be created from a fully charged capacitor bank by turning on and off the IGBT quickly. This allows the user to generate several short pulses in close proximity to each other as there is no need (or less need) to recharge the capacitor between the pulses.

    [0021] FIG. 3 is block diagram of a capacitive discharge welder in an exemplary embodiment according to the present invention. As can be seen in FIG. 3, the capacitive discharge welder includes a charging circuit 310 that takes incoming electricity and charges a capacitor bank 320, the capacitor bank 320 for storing energy, a semiconductor switching device 330 (e.g., IGBT or any other suitable semiconductor switching device) that connects and disconnects the capacitor bank 320 and the pulse transformer 340, a pulse transformer 340 that reduces the voltage from that stored in the capacitor bank 320 to the desired welding voltage, and a secondary circuit 350 electrically connected to the output of the pulse transformer 340 supplies a welding current corresponding to the output of the pulse transformer 340 to the material being welded (e.g., welding part 360). A controller 335 provides control signals to the IGBT 330 to control turning on and off of the IGBT, thereby selectively coupling the capacitor bank 320 to the pulse transformer 340. The controller 335, for example, may be programmed to turn off the IGBT after a delay and/or to rapidly turn the IGBT off and on.

    [0022] Therefore, the above embodiment of the present invention includes an improved type of electric switching element (i.e., a semiconductor switching device such as an IGBT). This improved switch allows the current to be shut off before the capacitors are discharged. This allows faster cycle times for the welding, reduced time between pulses in multi-pulse welding, reduced energy consumption, less waste heat generated within the control, and adjustable pulse durations for improved or optimum welding.

    [0023] FIG. 4 is a plot that shows an oscilloscope trace of two waveforms. The secondary waveform 401 shows the secondary current of a CD welder fired through a large fixed load (e.g., a giant resistor that does not heat up and change resistance during this type of weld pulse). The primary waveform 402 shows the current in the primary side of welder.

    [0024] As indicated in FIG. 4, each division in the horizontal direction represents 2 ms. Further, for the secondary waveform 401, each division in the vertical direction represents about 5000A and for the primary waveform 402, each division in the vertical direction represents about 150A. It can be seen that the switch is closed at time A to supply energy to the primary side (shown in the primary waveform 402) of the pulse transformer. Then the current across the secondary coil (shown in the secondary waveform 401) also starts to increase.

    [0025] It can be seen in FIG. 4 that during the second half of the weld, starting at about time B, the primary current starts to go back up as shown in the waveform 402, while the secondary current does not increase (e.g., as shown by the decrease in the waveform 401). Hence, the primary current is increased without an increase in secondary current, indicating lower impedance during the latter part of the weld. The second "hump" is due to transformer saturation and that the secondary output at this stage would be largely independent of the primary input. Therefore, more current is being applied to the primary side, and not getting more useful energy out of the secondary side.

    [0026] In one exemplary embodiment, the IGBT is cut off after a user programmed delay. The primary current could be cut off as the transformer reached saturation, and that this would have very little effect on the waveform of the secondary current.

    [0027] FIG. 5 is a plot of an oscilloscope trace when the primary current is shut off by the IGBT shortly after the primary current starts to increase again according to one exemplary embodiment of the present invention. The secondary waveform 501 shows the secondary current of a CD welder fired through a large fixed load (e.g., a giant resistor that does not heat up and change resistance during this type of weld pulse). The primary waveform 502 shows the current in the primary side of welder.

    [0028] As indicated in FIG. 5, each division in the horizontal direction represents 2 ms. Further, for the secondary waveform 501, each division in the vertical direction represents about 5000A, and for the primary waveform 502, each division in the vertical direction represents about 150A. It can be seen that the switch is closed at time C to supply energy to the primary side (shown in the primary waveform 502) of the pulse transformer. Then the current across the secondary coil (shown in the secondary waveform 501) also starts to increase.

    [0029] It can be seen in FIG. 5 that the primary current drops off sharply at about time D as indicated by the drop in the primary waveform 502, and the total energy output (the integrated area under the curve) is decreased dramatically (as compared with the primary waveform 402 of FIG. 4), but that the secondary pulse as illustrated by secondary waveform 501 has only a small reduction when compared with the first pulse (i.e., the secondary waveform 401 of FIG. 4).

    [0030] A second known issue with CD welders is that the rate of rise of the current into the weld is rapid. In some conditions, this can be desirable. However, if the parts to be welded contain a resistive coating such as an oxide that forms while the parts are waiting to be assembled, a plating that can degrade or interfere with the weld, or if the parts themselves do not fit together well as they are placed in the weld fixture, then this fast rate of rise of current is undesirable. In the conditions mentioned above (and in similar conditions) the rapid rate of rise of current often leads to weld expulsion and sub-optimal weld strength.

    [0031] If the rate of rise at which the current is put into the weld can be decreased, then the oxides or plating can be displaced before the peak weld current flows. This reduces the chance of expulsion. Similarly, if more time passes before peak weld current, parts that do not fit together well have some time during which to deform and fit together better before the peak weld current. Traditionally, CD welders have had different tap settings on their pulse transformer to change the duration of the entire weld pulse to deal with these conditions. However, these differing tap settings (differing primary to secondary windings ratios in the transformer) have substantially changed not only the rate at which the current rises into the weld, but also the overall timing during which the current flows. In addition, the peak voltage available to the weld changes with these settings.

    [0032] An example of the energy input for a "traditional" or unswitched CD weld in an exemplary embodiment according to the present invention is illustrated in FIG. 6. For example, the waveform 600 of FIG. 6 can be generated by a capacitive discharge welder of FIG. 2 or FIG. 3.

    [0033] In an exemplary embodiment according to the present invention, a capability to modify the rate at which energy is put into the discharge circuit is provided. In this embodiment, a capability is added to rapidly switch the semiconductor on and off multiple times during the initial energy input time while the current is rising. This repeated rapid switching of the semiconductor lengthens the time required to reach peak current. The discharge circuit may also be used to prevent saturation as described above.

    [0034] In one embodiment, the IGBT is rapidly switched on and off at least 4 or 5 times. In another embodiment, the IGBT is rapidly switched on and off 15-20 times. In yet another embodiment, the IGBT is rapidly switched on and off on the order of 20 times over a period of about 1-3 ms. However, the present invention is not limited thereto. In the embodiments of the present invention, the number of times and exact timing may be controlled (e.g., through software control) and changed.

    [0035] Returning now to FIG. 6, FIG. 6 illustrates a waveform 600 of the rising waveform of the energy input into the weld represented by voltage over time. In FIG. 6, each division in the horizontal direction represents 2 ms, and each division in the vertical direction represents about 1000A. It can be seen in FIG. 6 that the waveform 600 reaches its peak less than 2 ms (e.g., about 1.5 ms) after the energy/current is first applied to the weld. The peak of the waveform 600 is at about 5600A.

    [0036] FIG. 7 illustrates a waveform 700 of the rising waveform of the energy input into the weld represented by voltage over time, according to one exemplary embodiment of the present invention. Unlike FIG. 7, the switch (e.g., IGBT 204 of FIG. 2) is rapidly and repeatedly turned on and off to increase the rise time of the waveform, and reduce the peak energy level. By way of example, in one embodiment, the switch is turned on and off multiple (e.g., about 20) times over a time period (e.g., about 2 ms). The on/off period and timing may be variable. By way of example, the switching on and off may have a 10% duty cycle initially, then move to 90%. In one embodiment, the time on and time off may change throughout the multiple pulses being applied. However, the present invention is not limited thereto. The transient response (or noise) of the waveform 700 during the repeated, rapid switching of the switch is shown in FIG. 7.

    [0037] In FIG. 7, each division in the horizontal direction represents 2 ms, and each division in the vertical direction represents about 1000A. It can be seen in FIG. 8 that the waveform 700 reaches its peak about 2.8 ms after the energy/current is first applied to the weld. The peak of the waveform 700 is at about 5300A.

    [0038] Therefore, it can be seen by comparing FIGs. 6 and 7 that the peak energy is later in the pulse of waveform 700 compared to the waveform 600, and occurs at a somewhat lower level. This upslope feature helps the users to compensate for plating variation, surface contamination and/or poor "fit-up" between the parts to be welded. This repeated, rapid on-off switching method may also result in only limited losses in the semiconductor. Therefore, by repeatedly and rapidly switching the current on and off during the initial period of the weld, the time that it takes for the current to reach the peak can be extended.

    [0039] A third known issue with CD welders is the means of welding small parts or parts with limited thermal capacity. This problem is most often noted on thin conductive foils that are welded to traces on substrates such at printed wiring boards. In order to get a good weld, a high peak current and a rapid rate of rise is required for this type of weld. However, the total thermal energy input to the welded joint must be minimized in order to prevent damage to the substrate. In this case, the energy input to the weld after the peak current occurs goes primarily to heating the part (thus increasing the risk of damaging the substrate) and does not contribute substantially to the strength of the weld.

    [0040] A fourth issue with CD welders is the need to maximize the throughput of the welder. A fundamental requirement of the weld system is that the energy taken out of the capacitor bank in welding must be replenished before the next weld. Traditional CD welders using SCRs for switching must fully deplete the capacitor bank and see the voltage across the SCR fall to zero before they turn off. This extended discharge takes additional time (often on the order of 50 to 100 ms per weld) and dissipates additional energy from the capacitors, thus extending the time required to recharge them for the next weld.

    [0041] In one exemplary embodiment according to the present invention, short, low energy pulses could be created from a fully charged capacitor bank by turning on and off the IGBT quickly. This allows the user to generate several short pulses in close proximity to each other as there is no need to recharge the capacitor bank between each pulse. The capability of doing one short pulse and leaving the capacitor bank with a nearly complete charge was demonstrated using an embodiment of the present invention.

    [0042] The capability to do one short pulse for thin film conductive welds was also demonstrated. A graphical depiction of that waveform is shown in FIG. 8, which shows a short duration rapid rise weld pulse as a waveform 800. In FIG. 8, each division in the vertical direction represents about 1000A and each division in the horizontal direction represents 5 ms. The waveform 800 reaches a peak current of about 6700A at about 1 ms. However, the present invention is not limited thereto. This waveform 800 also demonstrates the short duration required before the capacitor recharge can begin. It can be seen in FIG. 8 that the weld pulse turns OFF at the 2 ms time. The periodic noise on the signal for the rest of the time period shown above is the charging circuit for the capacitors. It can be seen that the recharging starts much faster than the typical 100 ms from traditional SCR switched CD welders.


    Claims

    1. A capacitive discharge welder (300) comprising:

    a capacitor bank (320) for storing energy;

    a pulse transformer (340) for converting a first voltage stored in the capacitor bank (320) to a second voltage;

    a secondary circuit (350) electrically connected to the pulse transformer (340), the secondary circuit (350) for supplying a welding current corresponding to an output having the second voltage of the pulse transformer (340) to a part to be welded, wherein an energy delivered by the secondary circuit (350) depends only upon the value of the capacitor bank and the first voltage according to the formula E= ½ CV2 where E is the energy supplied, C is the capacitance of the capacitor bank (320), and V is the first voltage stored in the capacitor bank (320),

    characterized by an insulated gate bipolar transistor (IGBT) for selectively electrically connecting the capacitor bank (320) to the pulse transformer (340); a controller (335) adapted to output a control signal to turn the IGBT (330) on and off, wherein

    the controller (335) is adapted to turn off the IGBT (330) at a point shortly after primary current supplied to a primary side of the pulse transformer (340) starts to further increase while secondary current supplied by a secondary side of the pulse transformer (340) does not increase.


     
    2. The capacitive discharge welder of claim 1, wherein the controller is adapted to turn off the IGBT after a delay to avoid a saturation of the pulse transformer.
     
    3. The capacitive discharge welder of claim 2, wherein the delay is user-programmable.
     
    4. The capacitive discharge welder of claim 1, wherein the controller (335) is further adapted to repeatedly turn the IGBT (330) on and off rapidly at a start of welding to reduce a rate of rise of the welding current.
     
    5. The capacitive discharge welder of claim 4, wherein the controller (335) is adapted to rapidly turn the IGBT on and off at least 4 or 5 times at the start of the welding.
     
    6. The capacitive discharge welder of claim 1, wherein the controller (335) is further adapted to turn the IGBT on and off rapidly once to generate a short pulse.
     
    7. The capacitive discharge welder of claim 1, wherein the second voltage has a voltage level that is lower than that of the first voltage.
     
    8. A method of welding a part using a capacitive discharge welder (300) comprising a capacitor bank (320) for storing energy, a pulse transformer (340) for converting a first voltage stored in the capacitor bank to a second voltage, and a secondary circuit (350) for supplying a welding current corresponding to an output having the second voltage of the pulse transformer (340) to a part to be welded, the method comprising:

    applying the welding current to the part to be welded by electrically connecting the capacitor bank (320) to the pulse transformer (340) to supply energy; and

    turning off the welding current prior to a saturation of the pulse transformer (340) by electrically disconnecting the capacitor bank (320) from the pulse transformer (340),

    wherein an energy delivered by the secondary circuit (350) depends only upon the value of the capacitor bank and the first voltage according to the formula E= ½ CV2 where E is the energy supplied, C is the capacitance of the capacitor bank (320), and V is the first voltage sored in the capacitor bank (320), and

    characterized in that

    turning off the welding current includes turning off an insulated gate bipolar transistor (IGBT) selectively electrically connecting the capacitor bank (320) to the pulse transformer (340) at a point shortly after primary current supplied to a primary side of the pulse transformer (340) starts to further increase while secondary current supplied by a secondary side of the pulse transformer (340) does not increase.


     
    9. The method of claim 8, wherein the capacitor bank (320) is electrically disconnected from the pulse transformer (340) prior to near depletion of energy stored in the capacitor bank (320).
     
    10. The method of claim 9, wherein the capacitor bank (320) is electrically disconnected after a programmable delay.
     
    11. The method of claim 8, wherein the welding current is repeatedly turned on and off quickly at a start of the welding to reduce a rate of rise of the welding current.
     
    12. The method of claim 11, wherein the welding current is rapidly turned on and off at least 4 or 5 times at the start of the welding.
     
    13. The method of claim 8, wherein the welding current is turned on and off quickly once to generate a short pulse corresponding to the current.
     


    Ansprüche

    1. Kondensatorschweißmaschine (300), umfassend:

    eine Kondensatorbank (320) zum Speichern von Energie;

    einen Impulstransformator (340) zum Umwandeln einer in der Kondensatorbank (320) gespeicherten ersten Spannung in eine zweite Spannung;

    einen Sekundärkreis (350), der elektrisch mit dem Impulstransformator (340) verbunden ist, wobei der Sekundärkreis (350) zum Zuführen eines Schweißstroms, der einer Ausgabe mit der zweiten Spannung des Impulstransformators (340) entspricht, an ein zu schweißendes Teil dient, wobei eine von dem Sekundärkreis (350) gelieferte Energie nur vom Wert der Kondensatorbank und der ersten Spannung gemäß der Formel E = ½ CV2 abhängt, wobei E die zugeführte Energie ist, C die Kapazität der Kondensatorbank (320) ist und V die in der Kondensatorbank (320) gespeicherte erste Spannung ist,

    gekennzeichnet durch

    einen Bipolartransistor mit isoliertem Gate (IGBT) zum selektiven elektrischen Verbinden der Kondensatorbank (320) mit dem Impulstransformator (340);

    eine Steuerung (335), die dazu ausgelegt ist, ein Steuerungssignal auszugeben, um den IGBT (330) ein- und auszuschalten, wobei

    die Steuerung (335) dazu ausgelegt ist, den IGBT (330) an einem Punkt, kurz nachdem ein einer Primärseite des Impulstransformators (340) zugeführter Primärstrom beginnt, weiter zuzunehmen, während von einer Sekundärseite des Impulstransformators (340) zugeführter Sekundärstrom nicht zunimmt, auszuschalten.


     
    2. Kondensatorschweißmaschine nach Anspruch 1, wobei die Steuerung dazu ausgelegt ist, den IGBT nach einer Verzögerung auszuschalten, um eine Sättigung des Impulstransformators zu vermeiden.
     
    3. Kondensatorschweißmaschine nach Anspruch 2, wobei die Verzögerung vom Benutzer programmierbar ist.
     
    4. Kondensatorschweißmaschine nach Anspruch 1, wobei die Steuerung (335) ferner dazu ausgelegt ist, den IGBT bei einem Schweißbeginn wiederholt schnell ein- und auszuschalten, um eine Anstiegsrate des Schweißstroms zu reduzieren.
     
    5. Kondensationsschweißmaschine nach Anspruch 4, wobei die Steuerung (335) dazu ausgelegt ist, den IGBT bei dem Schweißbeginn mindestens 4 oder 5 Mal schnell ein- und auszuschalten.
     
    6. Kondensationsschweißmaschine nach Anspruch 1, wobei die Steuerung (335) ferner dazu ausgelegt ist, den IGBT einmal schnell ein- und auszuschalten, um einen kurzen Impuls zu erzeugen.
     
    7. Kondensatorschweißmaschine nach Anspruch 1, wobei die zweite Spannung einen Spannungspegel aufweist, der niedriger ist als derjenige der ersten Spannung.
     
    8. Verfahren zum Schweißen eines Teils unter Verwendung einer Kondensatorschweißmaschine (300), die eine Kondensatorbank (320) zum Speichern von Energie, einen Impulstransformator (340) zum Umwandeln einer in der Kondensatorbank gespeicherten ersten Spannung in eine zweite Spannung und einen Sekundärkreis (350) zum Zuführen eines Schweißstroms, der einer Ausgabe mit der zweiten Spannung des Impulstransformators (340) entspricht, an ein zu schweißendes Teil umfasst, wobei das Verfahren umfasst:

    Anlegen des Schweißstroms an das zu schweißende Teil durch elektrisches Verbinden der Kondensatorbank (320) mit dem Impulstransformator (340), um Energie zuzuführen; und

    Abschalten des Schweißstroms vor einer Sättigung des Impulstransformators (340) durch elektrisches Trennen der Kondensatorbank (320) von dem Impulstransformator (340),

    wobei eine von dem Sekundärkreis (350) gelieferte Energie nur vom Wert der Kondensatorbank und der ersten Spannung gemäß der Formel E = ½ CV2 abhängt, wobei E die zugeführte Energie ist, C die Kapazität der Kondensatorbank (320) ist und V die in der Kondensatorbank (320) gespeicherte erste Spannung ist, und

    dadurch gekennzeichnet, dass

    das Abschalten des Schweißstroms ein Ausschalten eines Bipolartransistors mit isoliertem Gate (IGBT), der die Kondensatorbank (320) mit dem Impulstransformator (340) selektiv elektrisch verbindet, an einem Punkt, kurz nachdem ein einer Primärseite des Impulstransformators (340) zugeführter Primärstrom beginnt, weiter zuzunehmen, während von einer Sekundärseite des Impulstransformators (340) zugeführter Sekundärstrom nicht zunimmt, umfasst.


     
    9. Verfahren nach Anspruch 8, wobei die Kondensatorbank (320) elektrisch von dem Impulstransformator (340) getrennt wird, bevor die in der Kondensatorbank (320) gespeicherte Energie beinahe erschöpft ist.
     
    10. Verfahren nach Anspruch 9, wobei die Kondensatorbank (320) nach einer programmierbaren Verzögerung elektrisch getrennt wird.
     
    11. Verfahren nach Anspruch 8, wobei der Schweißstrom bei einem Schweißbeginn wiederholt schnell an- und abgeschaltet wird, um eine Anstiegsrate des Schweißstroms zu reduzieren.
     
    12. Verfahren nach Anspruch 11, wobei der Schweißstrom bei dem Schweißbeginn mindestens 4 oder 5 Mal schnell an- und abgeschaltet wird.
     
    13. Verfahren nach Anspruch 8, wobei der Schweißstrom einmal schnell an- und abgeschaltet wird, um einen dem Strom entsprechenden kurzen Impuls zu erzeugen.
     


    Revendications

    1. Soudeuse à décharge capacitive (300) comprenant :

    une batterie de condensateurs (320) pour stocker l'énergie ;

    un transformateur d'impulsions (340) pour convertir une première tension stockée dans la batterie de condensateurs (320) en une seconde tension ;

    un circuit secondaire (350) connecté électriquement au transformateur d'impulsions (340), le circuit secondaire (350) étant destiné à alimenter une pièce à souder avec un courant de soudage correspondant à une sortie ayant la seconde tension du transformateur d'impulsions (340), dans lequel une énergie fournie par le circuit secondaire (350) dépend uniquement de la valeur de la batterie de condensateurs et de la première tension selon la formule E = ½ CV2, où E est l'énergie alimentée, C est la capacitance de la batterie de condensateurs (320), et V est la première tension stockée dans la batterie de condensateurs (320),

    caractérisée par

    un transistor bipolaire à porte isolée (IGBT) pour connecter électriquement de manière sélective la batterie de condensateurs (320) au transformateur d'impulsions (340) ;

    un contrôleur (335) adapté pour sortir un signal de commande afin d'allumer et de couper l'IGBT (330), dans lequel

    le contrôleur (335) est adapté pour couper l'IGBT (330) à un moment brièvement après que le courant primaire alimenté sur un côté primaire du transformateur d'impulsions (340) commence à continuer à augmenter tandis que le courant secondaire alimenté par un côté secondaire du transformateur d'impulsions (340) n'augmente pas.


     
    2. Soudeuse à décharge capacitive selon la revendication 1, dans laquelle le contrôleur est adapté pour couper l'IGBT après un délai pour éviter une saturation du transformateur d'impulsions.
     
    3. Soudeuse à décharge capacitive selon la revendication 2, dans laquelle le délai peut être programmé par l'utilisateur.
     
    4. Soudeuse à décharge capacitive selon la revendication 1, dans laquelle le contrôleur (335) est en outre adapté pour allumer et couper de manière répétée l'IGBT (330) rapidement au démarrage d'un soudage afin de diminuer une vitesse d'augmentation du courant de soudage.
     
    5. Soudeuse à décharge capacitive selon la revendication 4, dans laquelle le contrôleur (335) est adapté pour allumer et couper rapidement l'IGBT au moins 4 ou 5 fois au démarrage du soudage.
     
    6. Soudeuse à décharge capacitive selon la revendication 1, dans laquelle le contrôleur (335) est en outre adapté pour allumer et couper l'IGBT rapidement une fois afin de générer une courte impulsion.
     
    7. Soudeuse à décharge capacitive selon la revendication 1, dans laquelle la seconde tension a un niveau de tension qui est inférieur à celui de la première tension.
     
    8. Procédé destiné à souder une pièce en utilisant une soudeuse à décharge capacitive (300) comprenant une batterie de condensateurs (320) pour stocker l'énergie, un transformateur d'impulsions (340) pour convertir une première tension stockée dans la batterie de condensateurs en une seconde tension, et un circuit secondaire (350) pour alimenter une pièce à souder avec un courant de soudage correspondant à une sortie ayant la seconde tension du transformateur d'impulsions (340), le procédé comprenant :

    alimenter la pièce à souder avec un courant de soudage en connectant électriquement la batterie de condensateurs (320) au transformateur d'impulsions (340) pour alimenter l'énergie ; et

    couper le courant de soudage avant une saturation du transformateur d'impulsions (340) en déconnectant électriquement la batterie de condensateurs (320) du transformateur d'impulsions (340),

    dans laquelle une énergie fournie par le circuit secondaire (350) dépend uniquement de la valeur de la batterie de condensateurs et de la première tension selon la formule E = ½ CV2, où E est l'énergie alimentée, C est la capacitance de la batterie de condensateurs (320), et V est la première tension stockée dans la batterie de condensateurs (320), et

    caractérisé en ce que

    la coupure du courant de soudage comporte la coupure d'un transistor bipolaire à porte isolée (IGBT) connectant électriquement de manière sélective la batterie de condensateurs (320) au transformateur d'impulsions (340) à un moment brièvement après que le courant primaire alimenté sur un côté primaire du transformateur d'impulsions (340) commence à continuer à augmenter tandis que le courant secondaire alimenté par un côté secondaire du transformateur d'impulsions (340) n'augmente pas.


     
    9. Procédé selon la revendication 8, dans laquelle la batterie de condensateurs (320) est déconnectée électriquement du transformateur d'impulsions (340) avant que l'énergie stockée dans la batterie de condensateurs (320) soit presque épuisée.
     
    10. Procédé selon la revendication 9, dans laquelle la batterie de condensateurs (320) est déconnectée électriquement après un délai programmable.
     
    11. Procédé selon la revendication 8, dans laquelle le courant de soudage est allumé et coupé de manière répétée rapidement au démarrage du soudage afin de diminuer une vitesse d'augmentation du courant de soudage.
     
    12. Procédé selon la revendication 11, dans laquelle le courant de soudage est allumé et coupé rapidement au moins 4 ou 5 fois au démarrage du soudage.
     
    13. Procédé selon la revendication 8, dans laquelle le courant de soudage est allumé et coupé rapidement une fois afin de générer une courte impulsion correspondant au courant.
     




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    Cited references

    REFERENCES CITED IN THE DESCRIPTION



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    Patent documents cited in the description