DE102022211926A1 - welding machine - Google Patents

Abstract

The innovation is a welding device with an active high-current rectifier (10) provided there for energy conversion, wherein a three-phase rectifier functions as the high-current rectifier (10), which comprises a rectifier circuit and, within the rectifier circuit, electronic current valves (14) for the targeted activation and deactivation of individual bridge branches of the rectifier circuit.

Description

The innovation proposed here concerns the technical field of electric welding machines and electric welding devices - hereinafter referred to collectively as electric welding devices or welding devices for short. These are connected to a power source for energy supply and the electric welding device has means for converting the electrical energy drawn from the power source. The power source is usually the respective low-voltage network in the network version for three-phase alternating current (three-phase current). The conversion takes place in order to make the electrical energy drawn usable for electric welding and is carried out by means of a rectifier. This comprises a rectifier circuit, i.e. a rectifier circuit from a group of possible rectifier circuits. The group comprises at least one B6 bridge circuit, an M3 three-pulse mid-point rectifier circuit and an M6 six-pulse mid-point rectifier circuit. The terms rectifier and rectifier circuit are sometimes used synonymously in accordance with common usage. The conversion takes place from the low-voltage network into a controllable DC extra-low voltage (IEC 60499; DC ≤ 120V).

A rectifier is a power converter, i.e. a device for converting current, in this case a device for generating a direct current from an alternating current supplied on the input side. Current conversion is generally the conversion of one or more electrical quantities in a power system using converter valves. A converter valve is a functional element that only carries the electrical current in one direction, the forward direction. A converter valve consists of a valve component or alternatively of several valve components, each of which is in the on or off state at the same time. Examples of valve components are diodes, thyristors and transistors.

The electrical connection of the converter valves and any other functional elements required results in a respective converter circuit. This comprises at least one, but usually several converter branches. Each part of the converter circuit that performs the function of a converter valve is a converter branch. The structural design of the converter valves required for a converter circuit is called a converter set or valve set. In the case of a rectifier or a rectifier circuit, these terms apply accordingly (converter circuit, rectifier circuit; converter set, rectifier set; current conversion, rectification, etc.). A current or rectifier valve is sometimes also referred to below as a valve for short.

Traditionally, switchable three-phase mains transformers with series-connected rectifier sets on the output/secondary side were used for energy conversion. Even today, arc welding machines still consist of a welding transformer with primary and secondary windings and a downstream welding rectifier. The welding rectifier consists of a plate rectifier with valve components in the form of silicon power diodes (hereinafter referred to as Si diodes). The high welding currents of up to approx. 600A (for example in MIG/MAG inert gas welding; with other arc processes such as submerged arc welding, welding currents of up to 1,500A are possible) require a distributed rectifier structure that can be easily circulated by cooling air. The welding rectifier is therefore usually designed as a plate rectifier. Press-in diodes connected in parallel are mounted in several rectangular cooling plates and connected to busbars on the DC side.

The disadvantage is the high forward voltage of around 1.1V of the Si diodes during operation. In conjunction with the high welding currents, this inevitably leads to considerable power losses. In order to achieve good cooling of the Si diodes, the Si diodes are arranged on a respective cooling plate and distributed over all of the cooling plates of the plate rectifier, and the individual cooling plates are lined up one behind the other in an insulated manner. The wide distribution of the cooling plates (plate distribution) ensures good convection cooling and forced cooling. However, the large-area distribution of the Si diodes with high welding currents at the same time requires correspondingly large, solid busbars. In large plate rectifiers with long current paths, line losses on the busbars lead to additional heating losses.

In low voltage applications up to 120V DC and at the same time high power requirements, high currents of up to several 100A and beyond into the kA range inevitably arise due to the power law (P = U × I). In MIG/MAG arc welding, the standard characteristic curve results from EN 60974-1 for example, a welding voltage of U = 14 + 0.05 I for I ≤ 600A, and 44V for I > 600A. This means that for practically relevant welding currents between 20A and 550A, welding voltages (low voltage) of 15V to 41.5V can be expected. Using the standard characteristic curve, the voltage curve for a medium-power MIG/MAG welding machine at the highest welding level can be easily visualized. According to the standard characteristic curve, for example, 26.89V standard welding voltage results at 257.8A standard welding current.

The representation in 1 shows a known B6 bridge circuit (or three-phase bridge), referred to below as B6 circuit, here with an example of an input-side transformer. This functions as a converter/rectifier circuit and is used to rectify a three-phase alternating current supplied on the input side, thus generating a direct current. A respective low-voltage network can be considered as the source of the three-phase alternating current. The B6 circuit is the usual circuit of a welding rectifier.

2 shows a graphical representation of the current, voltage and power ratios on a Si diode in a B6 circuit. The typical sine half-waves of the diode current with 1=257.8A (top) resulting from a B6 circuit generate a voltage drop of 1.21V (middle) in the forward direction when the current flows through the Si diode. This results in the diode power loss (bottom) with an instantaneous value of Pv = 312W power loss on the Si diode. This is repeated at mains frequency on all Si diodes in the B6 circuit, in a standard B6 circuit with lower and upper diode branches (valve branches) - two valve/diode branches in series together form a valve/diode section and in the case of a B6 circuit a half-bridge of the B6 circuit - both in the lower and upper Si diodes. Since in a B6 circuit (in contrast to an M3 three-pulse midpoint rectifier circuit and an M6 six-pulse midpoint rectifier circuit; hereinafter referred to as M3 circuit or M6 circuit) two valves (diodes) always form a valve section, the power loss occurs at a lower and upper valve and thus results in 2 × 312W = 624W. According to the standard characteristic curve, the welding power at the arc for the welding process is 26.89 V × 257.8A = 6,932W. This results in a rectifier efficiency of only 91% in relation to the arc power.

The power loss of a Si diode is in the order of 1 .. 1.3 W per ampere, while that of a Schottky diode is still 0.5 .. 0.9 W/A. In a bridge rectifier, this power loss is doubled due to the two valve branches through which the current always flows.

These unfavorable conditions have promoted the development of active rectifiers with actively controlled power semiconductors as valves, because active rectifiers have a significantly lower power loss than passive diode rectifiers due to the lower forward voltages of the actively controlled power semiconductors.

Active rectifiers have long been known from literature, especially in the field of communications technology, and are established in small-signal technology. They are used there, for example, for the distortion-free rectification of signals and control voltages. Active rectifiers have only recently found their way into power electronics and are usually limited to single-phase network applications (230V). The use of active rectifiers is not known for devices connected to a low-voltage network in the network version for three-phase alternating current in the lower kA range and in the low-voltage range (IEC 60499 DC ≤ 120V, AC ≤ 50V), especially welding equipment. Components or even ready-made active rectifiers for this are not available on the market.

One objective of the proposed innovation is to provide a welding machine with improved energy efficiency.

The object outlined above is achieved according to the invention by means of a welding device, hereinafter also referred to as a device (device for electric welding; welding device) or as an innovation, having the features of claim 1.

According to this, a rectifier provided for energy conversion (current conversion) in the welding device is designed in the form of an active high-current rectifier. A three-phase rectifier acts as an active high-current rectifier. The active high-current rectifier comprises a rectifier circuit, for example a basically known B6 circuit (B6 bridge circuit) or an M3 or M6 circuit. Within the rectifier circuit, the active high-current rectifier comprises electronic current valves, in particular current valves with electronic power semiconductor switching elements as valve components, for the targeted activation and deactivation of individual branches of the rectifier circuit (bridge branches).

Electronic power semiconductor switching elements include, for example, high-current transistors such as MOSFET transistors (hereinafter referred to individually as MOSFET and in the plural as MOSFETs) or other high-current electronic switching elements such as insulated gate bipolar transistors (IGBT) or thyristors.

The special feature of the welding machine proposed here is that the energy wall The rectifier circuit is controlled by means of an active high-current rectifier and that this comprises electronic current valves for the targeted activation and deactivation of individual bridge branches of the rectifier circuit, which are characterized by a considerably lower power loss compared to electronic components otherwise used in rectifier circuits, namely diodes, in particular Si diodes. The lower power loss and thus the increased energy efficiency is the advantage of the welding device proposed here.

The representation in 3 shows an active rectifier (known per se) with a B6 circuit as rectifier circuit. In comparison to the one in 1 In the circuit shown, specifically controllable electronic current valves are used as current converter valves (valves) instead of the Si diodes. Due to the targeted controllability of these current valves, the rectifier is an active rectifier. This applies to other rectifier circuits that are also fundamentally possible, for example an M3 or M6 circuit.

To the 3 The rectifier circuit shown shows 4 (analogous to the representation in 2 ) a graphical representation of the current, voltage and power ratios using a MOSFET as an example of an electronic power semiconductor switching element (valve component) of a B6 circuit. The typical sine half-waves of the MOSFET current with I=266A (top) resulting from a B6 circuit only produce a voltage drop of 0.236V (middle) in the forward direction when the current flows. This results in the MOSFET power loss (bottom) with an instantaneous value of only Pv = 62.8W. Here, too, this is repeated at mains frequency on all MOSFETs, in the usual B6 bridge circuit both in the MOSFETs of the lower and upper half of all half-bridges. Since in a B6 circuit (in contrast to an M3 or M6 circuit) two MOSFETs still form a rectifier path (valve path), the MOSFET power loss occurs in the lower and upper bridge branches and thus results in 2 × 62.8W = 125.6W.

According to the standard characteristic curve, the welding process results in a welding power of 27.3V × 266A = 7,261.8W at the arc. This results in a rectification efficiency of 98.3% for the active rectifier in relation to the arc power.

By using an active rectifier, the rectifier efficiency has improved from 91% to 98.3% in relation to the arc power. The power loss of the rectifier has been reduced by 79.9%. The energy conversion required to operate a welding device can therefore be carried out with almost no loss using an active rectifier.

Advantageous embodiments of the innovation proposed here are the subject of the further claims. References used within the claims indicate the further development of the subject matter of the claim referred to by the features of the respective dependent claim. They are not to be understood as a waiver of the achievement of independent, objective protection for the features or combinations of features of a dependent claim. Furthermore, with regard to an interpretation of the claims and the description, when a feature in a dependent claim is specified in more detail, it must be assumed that such a limitation does not exist in the respective preceding claims or in a more general embodiment of the device in question. Any reference in the description to aspects of dependent claims is therefore to be read expressly as a description of optional features, even without a special reference.

Advantageous embodiments of the welding device proposed here, which has an active high-current rectifier with electronic current valves for energy conversion, deal with the structural design of the high-current rectifier, the current flow in the area of the high-current rectifier and the placement of the components of the high-current rectifier. It has been shown that simply using an active high-current rectifier as a welding rectifier in a welding device already leads to improved energy efficiency, but that further improvements are also advantageous.

For this purpose, the following considers what result, in terms of design, a mere use of an active high-current rectifier as a welding rectifier could have led to and what disadvantages are associated with this.

Basically, a welding rectifier can be implemented on the basis of an active high-current rectifier in the form of a discrete THT structure (THT = Through-Hole Technology). In contrast to surface mounting (SMT), a THT structure, also known as through-hole mounting, is characterized by the fact that the components have wire connections and these are inserted through contact holes in a circuit board during assembly and then connected to a respective conductor track on the circuit board by soldering.

In such a welding rectifier implementation, several high-current transistors are connected in parallel as valve components and electrically connected to a converter valve using a THT structure. Each converter valve of this type replaces one of the Si diodes in the B6 circuit ( 1 ).

The representation in 5 shows an embodiment of such a converter valve. The parallel-connected transistors 1 (for example six transistors) are expediently arranged in a star shape on a carrier 2. The arrangement is preferably carried out on an insulated, suspended, conductive metal plate (for example an aluminum sheet), which then also functions as a cooling plate of a heat sink. A power supply can be provided centrally for all transistors 1 via a thick copper plate as the star center to the source connections of the transistors. This copper plate forms the center of the star-shaped transistors 1. The gate connection of the transistors 1 is made via a hexagonal circuit board 3 with an inner circular cutout, which leaves the area of the copper plate in the star center free. For the drain connection of the transistors 1, an upper copper plate is screwed onto the transistors 1 and connected to the carrier. The result is an assembly/valve set which realizes exactly one of a total of six bridge branches of a B6 circuit. To obtain a complete B6 circuit, six such modules, each with six individual MOSFETs, are required.

Such a structure is absolutely necessary when implementing an active high-current rectifier based on a B6 circuit due to the high currents that occur during electric welding. The disadvantage is that the material and assembly costs are considerable. In addition, a THT structure can usually only be assembled by hand, which also results in a considerable amount of time and an error and/or quality risk associated with manual work. Furthermore, the distributed structure of the bridge branches does not allow for short connection and electrical line paths. This also leads to line losses.

Due to these disadvantages, the applicant did not further pursue a fundamentally possible discrete design of a welding rectifier in the form of an active high-current rectifier based on a B6 circuit.

In order to reduce the assembly effort and at the same time reduce the line and connection losses, it was then considered to implement the individual bridge branches using SMD technology (SMD = Surface-Mounted Device). In order not to overload the circuit board, it is important to reinforce and cool the high-current conductor tracks with busbars and at the same time to use the busbars directly as rectifier connection lugs.

The representation in 6 shows a resulting assembly with two times six MOSFETs 4, which together form a bridge branch of the B6 circuit. Two of the total six current valves of the B6 circuit are therefore located on one assembly. To obtain a complete B6 circuit, three of these assemblies (SMD bridge branches) are connected together and screwed together.

In order to increase the current carrying capacity of the circuit board and to achieve the lowest possible contact resistance to the MOSFETs 4, the busbars 5 are screwed onto the circuit board 6 directly near the power semiconductors (MOSFETs 4).

This significantly increases the current carrying capacity of the circuit board 6, dissipates excess heat and conducts the alternating currents and the rectifier currents. In the illustration in 6 you can see the centrally mounted AC power rail 5 and the two DC power rails 5 (DC+, DC-) on the left and right. There is also an insulated cooling plate and/or a heat sink on the back.

To obtain a complete B6 circuit, at least three such assemblies, each with two times six (or more or less than six, depending on the load) MOSFETs 4 are required.

This solution is not yet optimal either. The main disadvantage is the still considerable assembly effort, especially in connection with the assembly of the busbars 5 and finally also in connection with the combination of three components to form a welding rectifier. Finally, the dimensions of the resulting welding rectifier are also unfavorable.

The solution finally arrived at by the Applicant is characterised by the use of a metal core printed circuit board (Metal Core PCB or MCPCB; 7 : Reference number 12) from: The rectifier circuit of the high-current rectifier is implemented on a metal core circuit board (at least one metal core circuit board). Preferably, the rectifier circuit of the high-current rectifier is implemented on exactly one metal core circuit board.

A metal core circuit board consists of a dielectric layer, a metal layer and a copper foil with high mechanical strength. The advantage of a metal core circuit board compared to the conventional circuit board based on epoxy and glass fiber in their five to ten times higher thermal conductivity, better heat distribution and a thickness up to ten times smaller than conventional architectures. The current valves are made with SMD components and current posts are used instead of busbars. All half bridges of the rectifier circuit, for example designed as a B6 circuit, are combined in a common power module.

Additionally or alternatively, it is advantageously provided that current bolts ( 7 : reference number 18).

A current bolt is used to electrically contact a circuit board and a conductor track there, as well as to electrically connect the conductor track to a current conductor, for example a current conductor designed as a busbar. An electrically conductive base body, in particular a cylindrical base body, functions as a current bolt, which is or can be electrically connected to the circuit board via a first section of its outer surface, in particular one of the two cylinder bases, and to the current conductor via a second section of its outer surface, in particular the other cylinder base.

Examples of a design of a current bolt are shown in the EN 10 2015 204 119 A1 .

It is advantageous that the current bolts are connected by soldering to the metal core circuit board and to at least one conductor track therein.

In an advantageous embodiment, at least one current bolt is provided for receiving the currents flowing during operation of the rectifier circuit, for example a B6 circuit, namely at least one current bolt for receiving the alternating currents supplied to the rectifier circuit during operation and at least one current bolt for receiving the direct current resulting during operation of the rectifier circuit.

In a particularly preferred embodiment, at least two electrically parallel current bolts are provided to absorb the currents flowing during operation of the rectifier circuit, for example a B6 circuit. The at least two electrically parallel current bolts absorb the currents flowing during operation in a favorable manner, have sufficient current-carrying capacity, especially in combination, heat up only moderately during operation and do not lead to any significant power losses. A particularly advantageous embodiment with at least two electrically parallel current bolts, which is specifically considered for a B6 circuit, is characterized in that two electrically parallel current bolts are provided to absorb the alternating currents and that three electrically parallel current bolts are provided to absorb the direct current. The alternating currents are the alternating currents supplied to the B6 circuit (rectifier circuit) when it is operating. The direct current is the direct current resulting from the operation of the B6 circuit (rectifier circuit).

The claims submitted with the application are suggested formulations without prejudice to the attainment of further protection. Since the features of the dependent claims in particular can constitute separate and independent inventions in view of the state of the art on the priority date, the applicant reserves the right to make these or other combinations of features previously only disclosed in the description and/or drawing the subject of independent claims or declarations of division. They can also contain independent inventions that have a design that is independent of the subject matter of the claims referred to.

The overall innovation proposed here is also the use of an active high-current rectifier for converting electrical energy in an electric welding device as described here and below and for use in electric welding.

Finally, the innovation proposed here is also a method for the targeted control of the electronic current valves included in the active high-current rectifier during operation of a welding device.

An embodiment of the invention is explained in more detail below with reference to the drawing. Corresponding objects or elements are provided with the same reference numerals in all figures.

The embodiment is not to be understood as a limitation of the invention. Rather, additions and modifications are also possible within the scope of the present disclosure, in particular those which, for example, are achieved by combining or modifying individual features in connection with those described in the general or specific description part and in the The features or method steps contained in the claims and/or the drawing can be inferred by the person skilled in the art with regard to the solution of the problem and, through combinable features, lead to a new object or to new method steps or sequences of method steps.

• 1 eine B6-Brückenschaltung,
• 2 Strom-, Spannungs- und Leistungsverhältnisse an einer Si-Diode der B6-Brückenschaltung aus 1,
• 3 eine B6-Brückenschaltung mit aktiven elektronischen Stromventilen,
• 4 Strom-, Spannungs- und Leistungsverhältnisse an einem der Ventilbauelemente der B6-Brückenschaltung aus 1,
• 5 und
• 6 eine Ausführungsform eines Gleichrichters auf Basis einer B6-Brückenschaltung,
• 7 eine Ausführungsform eines Gleichrichters (aktiver Hochstromgleichrichter) auf Basis einer B6-Brückenschaltung wie hier vorgeschlagen,
• 8 eine Ansteuerschaltung innerhalb der B6-Brückenschaltung und
• 9 ein Schweißgerät mit einem aktiven Hochstromgleichrichter gemäß 7.

Show it

• 1 a B6 bridge circuit,
• 2 Current, voltage and power ratios at a Si diode of the B6 bridge circuit from 1 ,
• 3 a B6 bridge circuit with active electronic current valves,
• 4 Current, voltage and power ratios at one of the valve components of the B6 bridge circuit from 1 ,
• 5 and
• 6 an embodiment of a rectifier based on a B6 bridge circuit,
• 7 an embodiment of a rectifier (active high-current rectifier) based on a B6 bridge circuit as proposed here,
• 8th a control circuit within the B6 bridge circuit and
• 9 a welding machine with an active high-current rectifier in accordance with 7 .

The representation in 1 shows an example of a rectifier circuit, a B6 bridge circuit as the basis for a rectifier. The illustration in 2 shows the current, voltage and power ratios at one of the valves (here a Si diode) of such a B6 bridge circuit when used as a welding rectifier.

The representation in 3 shows a B6 bridge circuit with - in contrast to the one in 1 shown circuit - converter valves (valves) in the form of active electronic current valves in each bridge branch as the basis for an active rectifier. The representation in 4 shows the current, voltage and power ratios at one of the valves of such a B6 bridge circuit when used as a welding rectifier, namely when used as an active high-current rectifier (active high-current welding rectifier).

The representations in 5 and 6 show embodiments of an active high-current welding rectifier of the applicant which are no longer pursued.

The representation in 7 shows, in the form of a schematically simplified electrical-construction equivalent circuit diagram, an embodiment of an active high-current welding rectifier 10 proposed here. This comprises a B6 circuit, which is known per se, as a rectifier circuit on a carrier in the form of a metal core circuit board 12. Other circuits are also possible in principle, for example an M3/M6 circuit.

The proposed active high-current welding rectifier 10 comprises a parallel connection of several electronic switching elements 16 as current valves (valves) 14 in each bridge branch. A respective plurality of the electronic switching elements 16 is shown in the illustration in 7 only indicated in a simplified schematic form. For example, four or six switching elements 16 connected in parallel come into consideration. The totality of the switching elements 16 connected in parallel forms a current valve (valve) 14 and each switching element 16 within the parallel circuit is a valve component 16. In the interest of maintaining the clarity of the illustration, only individual current valves 14 and switching elements/valve components 16 are designated by their reference number. High-current capable MOSFETs come into consideration in particular as valve components 16 of the current valves 14.

A metal core circuit board 12 as a carrier of the rectifier circuit and the flow valves 14 included therein has the advantage of a possible reduction in the necessary number of valve components 16. The good thermal properties of a metal core circuit board 12 allow - in comparison to a welding rectifier corresponding 6 - a change from six to five or fewer parallel valve components 16, in particular MOSFETs, in each bridge branch.

Another special feature is the use of high-current current bolts 18 for the supply and discharge of the currents flowing during operation of the active high-current welding rectifier 10, which is also referred to below as rectifier 10. In the illustration in 7 the current bolts 18 are shown schematically in a simplified form as cylinders, whereby a cylindrical shape is actually an optionally possible shape. Other spatial shapes are also possible, for example a cuboid shape. Here too, in the interest of maintaining the clarity of the illustration, only individual current bolts 18 are designated with their reference number.

Each current bolt 18 contacts a conductor track on the metal core circuit board 12. The electrically conductive contact with the conductor track preferably consists of a base surface (first base surface) of the current bolt 18 and the opposite base surface (second base surface) of the current bolt 18 serves as a contact point of the rectifier 10. The current bolts 18 are preferably soldered to the first base surface with the respective conductor track and additionally screwed to the metal core circuit board 12. The current bolts 18 are preferably fastened in the immediate spatial proximity to the connections of the current valves 14, particularly preferably directly above and below the respective valve outputs and inputs.

An additional special feature is that at least two electrically parallel current bolts 18 serve to supply and discharge the currents flowing during operation of the rectifier 10. In comparison to the welding rectifier in 6 The current bolts 18 electrically replace the flat current rails 5 still provided there.

In the embodiment shown, the three phases of the alternating current to be rectified are fed to the rectifier 10 via two parallel current bolts 18 (P2, P3, P4) and the resulting direct current is tapped via three parallel current bolts 18 (P1, P5). The embodiment of the rectifier 10 shown therefore has a double AC connection (P2, P3, P4) and a reinforced, namely triple, direct current connection (P1, P5), so that at least one current bolt 18 is located in the immediate vicinity of each current valve 14 and without significant conductor track connection lengths (short current paths).

All current bolts 18 are advantageously located on the same surface of the metal core circuit board 12. This has the advantage that contact can be made to the rectifier 10 from the same side and from exactly one side. Preferably, the free base surfaces of the current bolts 18 (i.e. the base surfaces opposite the base surfaces intended for contacting the conductor track) are provided with a threaded hole or a thread-free hole that functions as a socket or the like. The current-carrying conductors for connecting the rectifier can then be easily mounted from the one side mentioned above, i.e. "from above" as it were.

Preferably, a layout of the conductor tracks on the metal core circuit board 12 is characterized in that, with the positions of the current bolts 18 resulting from the layout, all current bolts 18 are moved close to the current valves 14, so that short line paths (short current paths) and low line resistances result.

The representation in 8th shows - schematically simplified - part of a control circuit 20. This is intended for the targeted activation of the current valves 14 included in the rectifier 10 and the respective rectifier circuit. Activation of a current valve 14 means the activation of the or each valve component 16 included in the respective current valve 14. The control circuit 20 includes a trigger circuit 22 and a locking circuit 24. The trigger circuit 22 generates a control signal 26 and the locking circuit generates a control signal 28.

In the graphical representation of the control circuit 20 in 8th In the center of the valve component 16 of a current valve 14 of the rectifier 10 is shown. The usual connections (drain, source, gate) are designated with the letters D, S and G. The valve component 16 is, for example, a power MOSFET, in any case an electronic component with a so-called parasitic diode.

The trigger circuit 22 monitors the drain-source voltage of the valve component 16, i.e. the voltage across the parasitic diode there. A zero crossing of this voltage is an indication of the start of the so-called natural commutation, i.e. the transition of the current flow from one bridge branch to another bridge branch of the rectifier 10. When this voltage crosses zero, a so-called soft switching of the valve component 16 is possible. Soft switching is useful and desirable in the case of the welding rectifier 10 in question, because at the zero crossing switching can be carried out without power and thus without loss or at least essentially without power/without loss. Otherwise resulting switching losses are thus avoided.

The zero crossing can be distorted during electric welding due to, for example, welding arc short circuits and the associated dynamic load changes. Therefore, in a particularly preferred embodiment of the innovation proposed here, this zero crossing is determined for all flow valves 14 for each valve component 16 included therein by means of the control circuit 20, and the respective flow valve 14, i.e. all valve components 16 included therein, is controlled by means of the control circuit 20 on the basis of this zero crossing.

The detection of the zero crossing is carried out by means of the trigger circuit 22. This is connected parallel to the drain-source path of exactly one valve component 16 of the respective current valve 14 and thus connected in parallel to its parasitic diode. The trigger circuit 22 senses the respective voltage across the drain-source path (drain-source voltage) and generates the control signal 26 when this voltage crosses zero. The control signal 26 could be fed directly to activate the current valve 14, namely to activate the valve components 16 included therein to their gate terminals, and in a simple embodiment of the control circuit 20, the control signal 26 is fed directly to the gate terminals of all valve components 16 included in the current valve 14 to be activated.

The control circuit 20 is - in the sense of a schematically simplified representation of the conditions - in the illustration in 8th shown using the example of exactly one valve component 16. In the case of a flow valve 14 with a plurality of valve components 16, as is the case with the circuit of the rectifier 10 proposed here according to 7 If this is the case, exactly one of the valve components 16 of each flow valve 14 is monitored by means of the control circuit 20 and the control signal 26 is then determined (directly or indirectly) for all valve components 16 comprised by the respective flow valve 14.

In an advantageous, but nevertheless optional embodiment of the control circuit 20, activation of a respective flow valve 14 and the valve components 16 included therein by means of the control circuit 20 should only be possible if other flow valves 14 (and the valve components 16 therein) have not also been activated at the same time. The locking circuit 24 is provided for this purpose. This is shown in the illustration in 8th as an AND gate. The locking circuit 24 is supplied with the control signal 26 and the control signals 26 of further control circuits 20, namely control circuits 20 of the current valves 14 in the parallel bridge branches, the latter in the case of an AND gate acting as a locking circuit 24, each at negating inputs. For this purpose, the current valve 14, which is the 8th shown valve component 16, symbolically designated with the letter "A" for differentiation. The flow valves 14 of the parallel bridge branches - not shown here - would be designated accordingly, for example, with the letters "B" and "C" and each have their own control circuit 20, which in turn generates a control signal 26. These control signals 26 are symbolically designated with "B" and "C" at the input of the locking circuit 24 shown. This indicates that they originate from the control circuits 20 of the flow valves 14 in the parallel bridge branches.

The locking circuit 24 generates a control signal 28. This is fed to the gate terminals of the valve components 16 included in the respective current valve 14, namely to all valve components 16 of the current valve 14 whose valve component 16 is monitored by means of the control circuit 20. The control signal 28 only has a level which causes an activation of the respective current valve 14 and the valve components 16 included thereby if, on the one hand, a zero crossing of the drain-source voltage of the valve component 16 takes place and, on the other hand, no current valve 14 in the parallel bridge branches has been activated by means of their respective control circuit 20.

Here, the above applies accordingly: The control circuit 20 and its locking circuit 24 are shown in 8th shown using the example of exactly one valve component 16. In the case of a flow valve 14 with a plurality of valve components 16, as is the case with the circuit of the rectifier 10 proposed here according to 7 If this is the case, exactly one of the valve components 16 of each flow valve 14 is monitored by means of the control circuit 20 and the control signal 26 is then indirect and the control signal 28 derived therefrom is directly intended for all valve components 16 comprised by the respective flow valve 14.

A hold-delete function with respect to the signals generated by the control circuit 20 is implemented, for example, by means of a hysteresis function with suitably selected on/off threshold values of the trigger circuit 22. The signal duration of the control signal 26 then results from the threshold values and the natural commutation.

In the case of valve components 16 without a parasitic diode, their wiring with a diode as an additional component comes into consideration. In this case, the above also applies accordingly to such valve components 16.

The representation in 9 shows - only in a schematically massively simplified form - a welding device 100 with an active high-current rectifier 10 as proposed here.

Individual aspects of the description presented here that are in the foreground can be briefly summarized as follows: A welding device 100 is specified with an active high-current rectifier 10 provided there for energy conversion, wherein a three-phase rectifier functions as the high-current rectifier 10, which as a rectifier circuit, for example, has a B6 circuit and within the rectifier circuit electronic current valves 14 for targeted activation and deactivation. activation of individual bridge branches of the rectifier circuit.

In a particular embodiment of such a welding device 100, the rectifier circuit of the high-current rectifier 10, in particular in a design as a B6 circuit, is implemented on exactly one metal core circuit board 12 and/or at least two electrically parallel current bolts 18 are provided to absorb the currents flowing during operation of the rectifier circuit. The latter, for example, in that two electrically parallel current bolts 18 are provided to absorb the alternating currents supplied to the rectifier circuit during operation, in particular in the form of a B6 circuit, and in that three electrically parallel current bolts 18 are provided to absorb the direct current resulting from operation of the rectifier circuit, in particular in the form of a B6 circuit.

Optionally, in such a welding device 100, the high-current rectifier 10 comprises a control circuit 20 for the targeted activation of a current valve 14 when a voltage across a parasitic diode of at least one valve component 16 of the current valve 14 passes through zero.

List of reference symbols

1

transistor

2

carrier

3

Circuit board

4

MOSFET

5

Busbar

6

Circuit board

10

active high current rectifier, rectifier

12

Metal core circuit board

14

Flow valve

16

Valve component, electronic switching element

18

Power bolt

20

Control circuit

22

Trigger circuit

24

Locking circuit

26

Control signal

28

Control signal

100

welding machine

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• DE 102015204119 A1 [0039]

Cited non-patent literature

• EN 60974-1 [0006]

Claims (7)

Welding device (100) with an active high-current rectifier (10) provided there for energy conversion, wherein the high-current rectifier (10) functions as a three-phase rectifier, which comprises a rectifier circuit and, within the rectifier circuit, electronic current valves (14) for the targeted activation and deactivation of individual bridge branches of the rectifier circuit, wherein the rectifier circuit functions as a B6 bridge circuit, wherein the rectifier circuit of the high-current rectifier (10) is implemented on a metal core circuit board (12), wherein current bolts (18) function as supply and discharge connections for the rectifier circuit of the high-current rectifier (10), wherein at least one current bolt (18) is provided to receive the alternating currents supplied to the rectifier circuit during operation of the rectifier circuit, and where at least one current bolt (18) is provided to receive the direct current resulting from the operation of the rectifier circuit, wherein the rectifier circuit has a control circuit (20) for activating the current valves (14) comprises valve components (16), wherein a point in time of the zero crossing of a drain-source voltage of at least one valve component (16) of the respective current valve (14) can be detected by means of the control circuit (20), namely by means of a trigger circuit (22) comprised by the control circuit (20), and wherein the respective current valve (14) can be activated by means of the control circuit (20) due to the detection of the zero crossing. Welding machine (100) to Claim 1 , wherein the rectifier circuit of the high-current rectifier (10) is realized on exactly one metal core circuit board (12). Welding machine (100) to Claim 1 or 2 , wherein two electrically parallel current bolts (18) are provided to absorb the alternating currents supplied to the rectifier circuit during operation, and wherein three electrically parallel current bolts (18) are provided to absorb the direct current resulting from operation of the rectifier circuit. Welding device (100) according to one of the preceding claims, wherein the high-current rectifier (10) has insulated gate bipolar transistors (IGBT), thyristors or MOSFETs as electronic valve components (16) of the current valves (14). Welding device (100) according to one of the preceding claims, wherein the current bolts (18) are connected to the metal core circuit board (12) by soldering to a conductor track there. Welding device (100) according to one of the preceding claims, wherein the control circuit (20) comprises a locking circuit (24), wherein the respective current valve (14) can only be activated by means of the locking circuit (24) if the zero crossing has been detected and no activation of a current valve (14) in the parallel bridge branches occurs at the same time. Method for operating a welding device according to one of the preceding claims, wherein the zero crossing of a drain-source voltage of at least one valve component (16) of the respective current valve (14) is detected by means of the control circuit (20), in particular by means of a trigger circuit (22) included in the control circuit (20), and the respective current valve (14) is activated due to the detection of the zero crossing.

Images