DE1061006B - Device for stabilizing an alternating current welding arc - Google Patents

Description

The subject of the German patent 1 002 097 is a device for stabilizing an alternating current welding arc, in which at the zero crossing of the current a capacitor jerks over a span-; .i voltage-dependent switching element and the arc gap is discharged, which is connected to the primary side Welding voltage lying impulse transformer is charged and its essential feature in it consists in that the core of the pulse transformer consists of an iron alloy, whose magnetic induction with increasing magnetic field strength rises steeply to an almost constant saturation value, and that it is already magnetically saturated at welding voltages of about 10 volts. This facility allows at the beginning of each half-wave of the alternating feed current, d. H. essentially with one frequency of approximately 100 Hz to generate relatively high and sharply delimited voltage pulses and to be superimposed on the welding voltage. This results in a satisfactory stabilization of the welding arc achieved.

Furthermore, a device for stabilizing an alternating current welding arc is already known, in which an ignition transformer is connected to welding voltage on the primary side and parallel on the secondary side is bridged by a charging capacitor, when it is discharged via an adjustable spark gap and a capacitor, possibly with attenuators, a high voltage pulse on the arc is given.

The invention addresses the same known problem per se. The invention has the task of to solve the same problem, but with even simpler means and, if possible, longer Voltage impulses which are intended to achieve an even more reliable stabilization of the arc and which also allow a tuning of capacitor and within small limits Secondary winding on resonance becomes possible.

The invention accordingly relates to a device for stabilizing an alternating current welding arc with a capacitor (charging capacitor) connected in parallel to the secondary winding of a primary side Welding voltage lying ignition transformer, in particular high voltage transformer, switched and when the current crosses zero, abruptly via a voltage-dependent, changeable switching element and the arc gap is discharged.

According to the invention, the set object is achieved in that the capacitor is dimensioned in such a way is that its charge energy is of the order of magnitude of the magnetic energy, possibly saturation energy, of the ignition transformer or to this is an integer ratio.

Means to stabilize
an AC welding arc

Applicant:
Society for Linde's ice machines

Corporation,

Branch office Höllriegelskreuth,
Höllriegelskreuth near Munich

Franz Tajbl, Pullach near Munich,

and Max Gillitzer, Munich,
have been named as inventors

As the investigations on which the invention is based have shown, this becomes simple Circuit and sizing arrangement achieved that on the secondary side of the ignition transformer, preferably High-voltage transformer, which does not need to be a pulse transformer, The alternating welding current produces voltage pulses that are precisely synchronous, which are also reflected in all Fluctuations in both the network and the welding circuit always synchronize automatically (if necessary with phase shift). Here come certain Ohmic and inductive limiting resistors, which are used in the device according to patent 1 002 097 for adaptation at various no-load voltages were required, in omission. The invention allows one completely safe charging and discharging of the charging capacitor and thus extremely smooth operation of the welding arc at a relatively low, non-disturbing frequency.

The variable, voltage-dependent switching element of the secondary circuit is preferably the Transformer, especially high-voltage transformer, in a known manner as a spark gap with adjustable spark length or adjustable electrode spacing educated. In a preferred embodiment of the invention, the tolerance is at Equality of charging energy of the charging capacitor and magnetic energy of the ignition transformer just like that great that these two simply by setting the changeable, voltage-dependent switching element,

909 560/364

Claims (4)

preferably the spark gap, can be adjusted to practically the same values while compensating for the tolerance. According to a special embodiment of the inventive concept, the adjustable, voltage-dependent switching element is set in such a way that at each zero crossing of the alternating welding current, either two equally large, immediately successive voltage pulses are generated or a single, twice as strong pulse is generated. If, due to any external circumstances, in particular the burning state of the welding arc, the first pulse should not have been sufficient to cause the arc to be re-ignited, the. The second impulse that follows shortly thereafter causes sufficient ionization in the arc gap, which guarantees that the arc burns evenly. The drawing shows, for example, an embodiment of the device according to the invention, ao FIG. 1 shows the circuit structure, while FIG. 2 shows the voltage profile at the electrode according to the invention. Insofar as the individual parts of the drawing correspond to those in the figures of patent 1 002 097, the same reference numerals have been chosen so that the difference between the two arrangements becomes clear. 1 means the secondary winding of the mains transformer, to which the electrode 3 of the welding arc burning between the welding electrode 3 and the workpiece 4 is connected via a choke 2. Parallel to this circuit is the high-voltage ignition transformer 6 with two additional taps, the secondary circuit of which is also located on the welding arc between the electrode 3 and the workpiece 4. The secondary winding 6 ′ is in series with a spark gap 10. The charging capacitor 9 is parallel to the secondary winding 6. 13 is an isolating capacitor which is connected upstream of the spark gap 10. The primary winding of the ignition transformer 6 has two additional taps so that it can be used for various welding transformers 1 with, for example, no-load voltages of 42 to 55 or approximately 55 to 72 volts. The capacitance of the capacitor 9 is dimensioned in such a way that its charging energy is equal to the magnetic energy of the transformer 6. The electrode spacing of the spark gap 10 can be changed and thus allows the capacitor 9 to be matched to the secondary winding 6 '. 14 and 15 are VHF chokes; 16 and 17 are additional drops to extend the pulse duration. 18 is a snubber capacitor. FIG. 2 shows the welding voltage diagram resulting when the circuit arrangement shown in FIG. 1 is operated, the voltage U being plotted on the ordinate against the time t shown on the abscissa. Patent claims: 1. Device for stabilizing an alternating current welding arc with a capacitor (charging capacitor) that is connected to welding voltage in parallel to the secondary winding of a primary side lying Z and transformers, especially high-voltage transformers, is switched and at zero crossing of the current suddenly via a voltage-dependent, changeable switching element and the arc gap is discharged, characterized in that the capacitor (9) is dimensioned so that its charging energy is of the order of magnitude of the magnetic energy, optionally saturation energy, of the ignition transformer (6) or to this in one is an integer ratio. 2. Device according to claim 1, characterized in that the voltage-dependent switching element is designed in a known manner as a variable spark gap (10). 3. Device according to one of claims 1 and 2, characterized in that the tolerance with the equality of the charging energy of the charging capacitor (9) and the magnetic energy of the Ignition transformer (6) is only so large that these two (6, 9) can only be adjusted by setting the variable, voltage-dependent switching element, preferably the spark gap (10), with compensation the tolerance can be adjusted to practically the same values. 4. Device according to one of claims 1 to 3, characterized in that the setting of the variable, voltage-dependent switching element (10) is made such that with each Zero crossing of the welding alternating current either two equally large, immediately following one another Voltage pulses are generated or a single, twice as strong pulse is generated. Considered publications:
German interpretative document No. 1005 662. 1 sheet of drawings © 909 560364 6.59