Patent Description:
A welding system according to the present invention is defined in claim <NUM>.

Where appropriate, the same or similar reference numerals are used in the figures to refer to similar or identical elements.

" The embodiments described herein are not limiting, but rather are exemplary only. It should be understood that the described embodiments are not necessarily to be construed as preferred or advantageous over other embodiments. Moreover, the term "embodiments" does not require that all embodiments of the disclosure include the discussed feature, advantage, or mode of operation.

As used herein, a wire-fed welding-type system refers to a system capable of performing welding (e.g., gas metal arc welding (GMAW), gas tungsten arc welding (GTAW), submerged arc welding (SAW), etc.), brazing, cladding, hardfacing, and/or other processes, in which a filler metal is provided by a wire that is fed to a work location, such as an arc or weld puddle.

As used herein, a welding-type power source refers to any device capable of, when power is applied thereto, supplying welding, cladding, plasma cutting, electrode preheating, induction heating, laser (including laser welding, laser hybrid, and laser cladding), carbon arc cutting or gouging and/or resistive preheating, including but not limited to transformer-rectifiers, inverters, converters, resonant power supplies, quasi-resonant power supplies, switch-mode power supplies, etc., as well as control circuitry and other ancillary circuitry associated therewith.

As used herein, preheating refers to heating the electrode wire prior to a welding arc and/or deposition in the travel path of the electrode wire. As used herein, the term "preheat voltage" refers to a measured voltage representative of the voltage across a section of electrode conducting preheating current, but not necessarily the exact voltage across that section.

Some disclosed examples describe electric currents being conducted "from" and/or "to" locations in circuits and/or power supplies. Similarly, some disclosed examples describe "providing" electric current via one or more paths, which may include one or more conductive or partially conductive elements. The terms "from," "to," and "providing," as used to describe conduction of electric current, do not necessitate the direction or polarity of the current. Instead, these electric currents may be conducted in either direction or have either polarity for a given circuit, even if an example current polarity or direction is provided or illustrated.

Disclosed example preheating power supplies include: power conversion circuitry configured to output welding-type power via a first output power connector and a second output power connector; and a bypass path prevention circuit configured to prevent less than a threshold voltage applied to the first output power connector and the second output power connector from a different power supply from causing current to flow between the first output power connector and the second output power connector.

In some examples, the bypass path prevention circuit includes a diode configured to increase a forward voltage drop from the first output power connector to the second output power connector. Some example preheating power supplies further include a controller configured to control the power conversion circuitry to output an electrode preheating voltage based on the forward voltage drop.

Some example preheating power supplies further include a switching element configured to selectively couple the first output power connector to the second output power connector; and a switching control circuit configured to selectively control the switching element to decouple the first output power connector and the second output power connector. In some examples, the switching control circuit is configured to control the switching element to decouple the first output power connector and the second output power connector when the power conversion circuitry is not outputting current via the first output power connector and the second output power connector. In some examples, the switching control circuit is configured to control the switching element to couple the first output power connector and the second output power connector when the power conversion circuitry is outputting current via the first output power connector and the second output power connector.

In some examples, the bypass path prevention circuit includes a resistor. In some examples, the bypass path prevention circuit includes a load switch. In some examples, the bypass path prevention circuit includes a negative temperature coefficient thermistor. In some examples, the welding-type power comprises electrode preheating current.

Disclosed example (not covered by the present invention) welding power source interconnection cables include: a first termination configured to be coupled to a first welding-type power connector; a second termination configured to be coupled to a second welding-type power connector; and a forward voltage increase circuit configured to increase a voltage drop from the first termination to the second termination.

Some example welding power source interconnection further include a third welding-type power connector connected to the first termination and configured to receive a third termination such that the third termination is connected to the first termination. In some examples, the forward voltage increase circuit includes a diode configured to set a minimum voltage required to conduct current from the first termination to the second termination. In some examples, the forward voltage increase circuit includes two or more diodes connected in series and configured to set the minimum voltage required to conduct current from the first termination to the second termination. In some examples, the forward voltage increase circuit includes a resistor. In some examples, the forward voltage increase circuit includes a negative temperature coefficient thermistor.

Referring to <FIG>, an example welding system <NUM> is shown in which a robot <NUM> is used to weld a workpiece <NUM> using a welding tool <NUM>, such as the illustrated bent-neck (i.e., gooseneck design) welding torch (or, when under manual control, a handheld torch), to which power is delivered by welding equipment <NUM> via conduit <NUM> and returned by way of a ground conduit <NUM>. The welding equipment <NUM> may comprise, inter alia, one or more power sources (each generally referred to herein as a "power supply"), a source of a shielding gas, a wire feeder, and other devices. Other devices may include, for example, water coolers, fume extraction devices, one or more controllers, sensors, user interfaces, communication devices (wired and/or wireless), etc..

The welding system <NUM> of <FIG> may form a weld (e.g., at weld joint <NUM>) between two components in a weldment by any known electric welding techniques. Known electric welding techniques include, inter alia, shielded metal arc welding (SMAW), MIG, flux-cored arc welding (FCAW), TIG, laser (e.g., laser welding, laser cladding, laser hybrid), sub-arc welding (SAW), stud welding, friction stir welding, and resistance welding. MIG, TIG, hot wire cladding, hot wire TIG, hot wire brazing, multiple arc applications, and SAW welding techniques, inter alia, may involve automated or semi-automated external metal filler (e.g., via a wire feeder). In multiple arc applications (e.g., open arc or sub-arc), the preheater may preheat the wire into a pool with an arc between the wire and the pool. Optionally, in any embodiment, the welding equipment <NUM> may be arc welding equipment having one or more power supplies, and associated circuitry, that provides a direct current (DC), alternating current (AC), or a combination thereof to an electrode wire <NUM> of a welding tool (e.g., welding tool <NUM>). The welding tool <NUM> may be, for example, a TIG torch, a MIG torch, or a flux cored torch (commonly called a MIG "gun"). The electrode wire <NUM> may be tubular-type electrode, a solid type wire, a flux-core wire, a seamless metal core wire, and/or any other type of electrode wire.

As will be discussed below, the welding tool <NUM> may employ a contact tip assembly that heats the electrode wire <NUM> prior to forming a welding arc using the electrode wire <NUM>, which provides multiple benefits for certain welding applications. Some of these benefits are disclosed in <CIT>, entitled "Systems, Methods, and Apparatus to Preheat Welding Wire.

In the welding system <NUM>, the robot <NUM>, which is operatively coupled to welding equipment <NUM> (e.g., welding and/or preheating equipment) via conduit <NUM> and ground conduit <NUM>, controls the location of the welding tool <NUM> and operation of the electrode wire <NUM> (e.g., via a wire feeder) by manipulating the welding tool <NUM> and triggering the starting and stopping of the current flow (whether a preheating current and/or welding current) to the electrode wire <NUM> by sending, for example, a trigger signal to the welding equipment <NUM> (e.g., welding and/or preheating equipment). When welding current is flowing, a welding arc is developed between the electrode wire <NUM> and the workpiece <NUM>, which ultimately produces a weldment. The conduit <NUM> and the electrode wire <NUM> thus deliver welding current and voltage sufficient to create the welding arc between the electrode wire <NUM> and the workpiece <NUM>.

<FIG> is a block diagram illustrating preheating and welding current paths in a conventional welding system <NUM> using resistive preheating. The conventional welding system <NUM> includes a weld torch <NUM> having a first contact tip <NUM> and a second contact tip <NUM>. The system <NUM> further includes an electrode wire <NUM> fed from a wire spool <NUM>, a preheating power supply <NUM>, and a welding power supply <NUM>. The system <NUM> is illustrated in operation as producing a welding arc <NUM> between the electrode wire <NUM> and a workpiece <NUM>.

In operation, the electrode wire <NUM> passes from the wire spool <NUM> through the second contact tip <NUM> and the first contact tip <NUM>, between which the preheating power supply <NUM> generates a preheating current to heat the electrode wire <NUM>. Specifically, in the configuration shown in <FIG>, the preheating current enters the electrode wire <NUM> via the second contact tip <NUM> and exits via the first contact tip <NUM>. At the first contact tip <NUM>, a welding current may also enter the electrode wire <NUM>. The welding current is generated, or otherwise provided by, the welding power supply <NUM>. The welding current exits the electrode wire <NUM> and returns via the workpiece <NUM>. When the electrode wire <NUM> makes contact with a target metal workpiece <NUM>, an electrical circuit is completed and the welding current flows through the electrode wire <NUM>, across the metal work piece(s) <NUM>, and returns to the welding power supply <NUM>. The welding current causes the electrode wire <NUM> and the parent metal of the work piece(s) <NUM> in contact with the electrode wire <NUM> to melt, thereby joining the work pieces as the melt solidifies. By preheating the electrode wire <NUM>, a welding arc <NUM> may be generated with reduced arc energy. Generally speaking, the preheating current is proportional to the distance between the contact tips <NUM>, <NUM> and the electrode wire <NUM> size.

The welding current is generated, or otherwise provided by, a welding power supply <NUM>, while the preheating current is generated, or otherwise provided by, the preheating power supply <NUM>. The preheating power supply <NUM> and the welding power supply <NUM> may ultimately share a common power source (e.g., a common generator or line current connection), but the current from the common power source is converted, inverted, and/or regulated to yield the two separate currents - the preheating current and the welding current. For instance, the preheat operation may be facilitated with a single power source and associated converter circuitry, in which case three leads may extend from a single power source.

During operation, the system <NUM> establishes a welding circuit <NUM> to conduct welding current, which is illustrated by a weld current path <NUM>. The weld current path <NUM> flows from the welding power supply <NUM> to the first contact tip <NUM> and returns to the welding power supply <NUM> via the welding arc <NUM>, the workpiece <NUM>, and a work lead <NUM>. To enable connection between the welding power supply <NUM> and the first contact tip <NUM> and the workpiece <NUM>, the welding power supply <NUM> includes terminals <NUM>, <NUM> (e.g., a positive terminal and a negative terminal).

During operation, the preheating power supply establishes a preheating circuit to conduct preheating current, which is represented by a preheat current path <NUM> through a section <NUM> of the electrode wire <NUM>. To enable connection between the preheating power supply <NUM> and the contact tips <NUM>, <NUM>, the preheating power supply <NUM> includes terminals <NUM>, <NUM>. The preheating current path <NUM> flows from the welding power supply <NUM> to the second contact tip <NUM>, the section <NUM> of the electrode wire <NUM>, the first contact tip <NUM>, and returns to the preheating power supply <NUM> via a cable <NUM> connecting the terminal <NUM> of the welding power supply <NUM> to the terminal <NUM> of the preheating power supply <NUM>.

Because the preheating current path <NUM> is superimposed with the welding current path <NUM> over the connection between the first contact tip <NUM> and the power supplies <NUM>, <NUM>, the cable <NUM> may enable a more cost-effective single connection between the first contact tip <NUM> and the power supplies <NUM>, <NUM> (e.g., a single cable) than providing separate connections for the welding current to the first contact tip <NUM> and for the preheating current to the first contact tip <NUM>.

As illustrated in <FIG>, the weld current may flow through second current path <NUM>, in which the current exits the terminal <NUM> of the welding power supply <NUM>, flows through the cable <NUM> to the terminal <NUM> of the preheating power supply <NUM>, exits the terminal <NUM> of the preheating power supply <NUM>, flows to the second contact tip <NUM>, through the electrode wire <NUM>, through the welding arc <NUM>, and through the workpiece <NUM>, and returns via the work lead <NUM> to the terminal <NUM> of the welding power supply <NUM> to complete the current path.

Because there are two paths <NUM>, <NUM> for the welding power source current, the welding current will split between the paths <NUM>, <NUM> in an inverse relationship to the resistance. The ratio of current in the paths <NUM>, <NUM> will be such that the current takes the path of least resistance and the total energy dissipated is minimized. Therefore, the current in the preheat current path <NUM> can vary substantially and cause inconsistency with arc starts.

Stated another way, a voltage between the terminal <NUM> and the first contact tip <NUM> provides a driving voltage <NUM> for current to flow through the preheating power supply <NUM>. The driving voltage <NUM> increases when the length of conductor between the terminal <NUM> and the first contact tip increases <NUM>.

<FIG> is a block diagram of an example welding system <NUM> using resistive preheating and including a forward voltage increase circuit <NUM> that reduces or prevents weld current flow through the preheating power supply <NUM>. The example welding system <NUM> of <FIG> includes the weld torch <NUM>, the first contact tip <NUM>, the second contact tip <NUM>, the electrode wire <NUM>, the wire spool <NUM>, the preheating power supply <NUM>, and the welding power supply <NUM>. In the example of <FIG>, the terminal <NUM> of the preheating power supply <NUM> is connected to the terminal <NUM> of the welding power supply <NUM>, and both terminals <NUM>, <NUM> are connected to the first contact tip <NUM>.

The example forward voltage increase circuit <NUM> reduces or prevents the weld current from traversing the current path <NUM> (illustrated in <FIG>) through the terminals <NUM>, <NUM> of the preheating power supply <NUM> by increasing a forward voltage <NUM> from the terminal <NUM> of the welding power supply <NUM> to the terminals <NUM> and <NUM> to a sufficiently high forward voltage (e.g., a higher voltage than the driving voltage <NUM>). The forward voltage may be configured based on the expected welding voltage range output by the welding power supply <NUM>. By increasing the forward voltage drop from the terminal <NUM> to the terminal <NUM>, the weld current flows through the current path <NUM> instead of to the preheating power supply <NUM>.

The forward voltage increase circuit <NUM> is part of a welding power source interconnection cable <NUM> connected between the terminals <NUM>, <NUM> of the power supplies <NUM>, <NUM>. The example interconnection cable <NUM> includes a first termination <NUM> that can be coupled to the terminal <NUM> of the welding power supply <NUM> and a second termination <NUM> that can be coupled to the terminal <NUM> of the preheating power supply <NUM>. The forward voltage increase circuit <NUM> increases a forward voltage <NUM> from the termination <NUM> to the termination <NUM>.

As illustrated in <FIG>, the terminal <NUM> of the preheating power supply <NUM> may be coupled to the electrode wire <NUM> via a contact point in a wire feeder <NUM> supplying the electrode wire <NUM>. An example contact point is a conductive roller of a wire drive motor <NUM> (e.g., an idle roller of the wire drive motor <NUM>).

The example wire feeder <NUM> may include a preheat controller <NUM> configured to provide preheating commands <NUM> (e.g., target current, target voltage, etc.) to the preheating power supply <NUM> based on voltage feedback <NUM>, <NUM> from the contact tips <NUM>, <NUM> and/or based on welding information <NUM> from the welding power supply <NUM>.

While example polarities are illustrated in <FIG>, and <FIG>, other polarities may be used where the preheating current at least partially cancels the welding current between the first contact tip <NUM> and the terminals <NUM>, <NUM>, <NUM>, <NUM> of the power supplies <NUM>, <NUM>.

<FIG> illustrates an example implementation of the welding power source interconnection cable <NUM> of <FIG>, including an example implementation of the forward voltage increase circuit <NUM> of <FIG>.

The example forward voltage increase circuit <NUM> includes one or more diodes <NUM> in series with the preheat current flow path such that the forward voltage drop of the diode(s) <NUM> is higher than that of the driving voltage <NUM> of <FIG>. Because the driving voltage <NUM> cannot overcome the forward voltage drop required by the diodes <NUM>, the added voltage drop provided by the diodes <NUM> may prevent the weld current from flowing to the preheating power supply <NUM> and cause the weld current to flow instead to the first contact tip <NUM> to follow the weld current path <NUM>.

The example forward voltage increase circuit <NUM> includes diodes <NUM> for either direction of current flow such that there is a current path regardless of polarity of the voltage across the forward voltage increase circuit <NUM>. In some other examples, the forward voltage increase circuit <NUM> only includes the diodes <NUM> in one direction, such that the forward voltage increase circuit <NUM> enables current flow in only one direction (e.g., polarity-dependent).

Additionally or alternatively, the forward voltage increase circuit <NUM> may include a resistance to divert more of the weld current to the first contact tip <NUM> away from the preheating power supply. Other circuits and/or circuit elements may also be used to reduce or prevent the flow of weld current through the cable <NUM>.

To enable connection of the weld cable <NUM> to the preheating power supply <NUM> and the welding power supply <NUM>, the example terminations <NUM>, <NUM> of <FIG> include standard welding connectors configured to be connected to welding studs, Euro-style connectors, and/or any other type of connector that may be found on a welding-type power supply. Additionally or alternatively, one or both of the terminations <NUM>, <NUM> may include a connector to be hard wired to a power bus of the power supplies <NUM>, <NUM>.

The example termination <NUM> of <FIG> includes a third connector <NUM>, such as a weld stud coupled to the termination <NUM>. The third connector <NUM> enables a second connection to be made (e.g., via a connector <NUM>) between the termination <NUM> and the first contact tip <NUM>. The third connector <NUM> provides the pathway for the welding current to flow between the terminal <NUM> and the first contact tip <NUM> (e.g., without traversing the preheating power supply <NUM>).

Instead of providing an interconnection cable as illustrated in <FIG>, the preheating power supply <NUM> is configured to reduce or prevent flow of welding current between the terminals <NUM>, <NUM> (e.g., from the terminal <NUM> to the terminal <NUM>). <FIG> is an example power supply <NUM> that is used to implement the preheating power supply <NUM> of <FIG>, and/or <NUM>, in which a bypass path prevention circuit <NUM> prevents the flow of weld current from the terminal <NUM> to the terminal <NUM>, while permitting preheating current to be output by the preheating power supply <NUM>. The bypass path prevention circuit <NUM> may be internal or external to a housing of the power supply <NUM>.

The example power supply <NUM> powers, controls, and supplies consumables to a welding application. In some examples, the power supply <NUM> directly supplies input power to the welding torch <NUM>. In the illustrated example, the welding power supply <NUM> is configured to supply welding power to welding operations and/or preheating power to preheating operations. The example power supply <NUM> may also provide power to a wire feeder to supply the electrode wire <NUM> to the welding torch <NUM> (e.g., for GMAW welding and/or flux core arc welding (FCAW)).

The power supply <NUM> receives primary power <NUM> (e.g., from the AC power grid, an engine/generator set, a battery, or other energy generating or storage devices, or a combination thereof), conditions the primary power, and provides an output power to one or more welding devices and/or preheating devices in accordance with demands of the system. The primary power <NUM> may be supplied from an offsite location (e.g., the primary power may originate from the power grid). The welding power supply <NUM> includes a power converter <NUM>, which may include transformers, rectifiers, switches, and so forth, capable of converting the AC input power to AC and/or DC output power as dictated by the demands of the system (e.g., particular welding processes and regimes). The power converter <NUM> converts input power (e.g., the primary power <NUM>) to welding-type power based on a weld voltage setpoint and outputs the welding-type power via a weld circuit.

In some examples, the power converter <NUM> is configured to convert the primary power <NUM> to both welding-type power and auxiliary power outputs. However, in other examples, the power converter <NUM> is adapted to convert primary power only to a weld power output, and a separate auxiliary converter is provided to convert primary power to auxiliary power. In some other examples, the power supply <NUM> receives a converted auxiliary power output directly from a wall outlet. Any suitable power conversion system or mechanism may be employed by the power supply <NUM> to generate and supply both weld and auxiliary power.

The power supply <NUM> includes a controller <NUM> to control the operation of the power supply <NUM>. The welding power supply <NUM> also includes a user interface <NUM>. The controller <NUM> receives input from the user interface <NUM>, through which a user may choose a process and/or input desired parameters (e.g., voltages, currents, particular pulsed or non-pulsed welding regimes, and so forth). The user interface <NUM> may receive inputs using any input device, such as via a keypad, keyboard, buttons, touch screen, voice activation system, wireless device, etc. Furthermore, the controller <NUM> controls operating parameters based on input by the user as well as based on other current operating parameters. Specifically, the user interface <NUM> may include a display <NUM> for presenting, showing, or indicating, information to an operator. The controller <NUM> may also include interface circuitry for communicating data to other devices in the system, such as the wire feeder. For example, in some situations, the power supply <NUM> wirelessly communicates with other welding devices within the welding system. Further, in some situations, the power supply <NUM> communicates with other welding devices using a wired connection, such as by using a network interface controller (NIC) to communicate data via a network (e.g., ETHERNET, 10BASE2, 10BASE-T, 100BASE-TX, etc.). In the example of <FIG>, the controller <NUM> communicates with the wire feeder via the weld circuit via a communications transceiver <NUM>.

The controller <NUM> includes at least one controller or processor <NUM> that controls the operations of the welding power supply <NUM>. The controller <NUM> receives and processes multiple inputs associated with the performance and demands of the system. The processor <NUM> may include one or more microprocessors, such as one or more "general-purpose" microprocessors, one or more special-purpose microprocessors and/or ASICS, and/or any other type of processing device. For example, the processor <NUM> may include one or more digital signal processors (DSPs).

The example controller <NUM> includes one or more storage device(s) <NUM> and one or more memory device(s) <NUM>. The storage device(s) <NUM> (e.g., nonvolatile storage) may include ROM, flash memory, a hard drive, and/or any other suitable optical, magnetic, and/or solid-state storage medium, and/or a combination thereof. The storage device <NUM> stores data (e.g., data corresponding to a welding application), instructions (e.g., software or firmware to perform welding processes), and/or any other appropriate data. Examples of stored data for a welding application include an attitude (e.g., orientation) of a welding torch, a distance between the contact tip and a workpiece, a voltage, a current, welding device settings, and so forth.

The memory device <NUM> may include a volatile memory, such as random access memory (RAM), and/or a nonvolatile memory, such as read-only memory (ROM). The memory device <NUM> and/or the storage device(s) <NUM> may store a variety of information and may be used for various purposes. For example, the memory device <NUM> and/or the storage device(s) <NUM> may store processor executable instructions <NUM> (e.g., firmware or software) for the processor <NUM> to execute. In addition, one or more control regimes for various welding processes, along with associated settings and parameters, may be stored in the storage device <NUM> and/or memory device <NUM>, along with code configured to provide a specific output (e.g., initiate wire feed, enable gas flow, capture welding data, detect short circuit parameters, determine amount of spatter) during operation.

In some examples, the welding power flows from the power converter <NUM> through a weld cable <NUM>. The example weld cable <NUM> is attachable and detachable from the terminals <NUM>, <NUM> at each of the welding power supply <NUM> (e.g., to enable ease of replacement of the weld cable <NUM> in case of wear or damage). Furthermore, in some examples, welding data is provided with the weld cable <NUM> such that welding power and weld data are provided and transmitted together over the weld cable <NUM>. The communications transceiver <NUM> is communicatively coupled to the weld cable <NUM> to communicate (e.g., send/receive) data over the weld cable <NUM>. The communications transceiver <NUM> may be implemented based on various types of power line communications methods and techniques. For example, the communications transceiver <NUM> may utilize IEEE standard P1901. <NUM> to provide data communications over the weld cable <NUM>. In this manner, the weld cable <NUM> may be utilized to provide welding power from the welding power supply 302a, 302b to the wire feeder and the welding tool <NUM>. Additionally or alternatively, the weld cable <NUM> may be used to transmit and/or receive data communications to/from the wire feeder and the welding torch <NUM>. The communications transceiver <NUM> is communicatively coupled to the weld cable <NUM>, for example, via cable data couplers <NUM>, to characterize the weld cable <NUM>, as described in more detail below. The cable data coupler <NUM> may be, for example, a voltage or current sensor.

The power supply <NUM> includes or is implemented in a wire feeder.

In some examples, a gas supply <NUM> provides shielding gases, such as argon, helium, carbon dioxide, mixed gases, and so forth, depending upon the welding application. The shielding gas flows to a valve <NUM>, which controls the flow of gas, and if desired, may be selected to allow for modulating or regulating the amount of gas supplied to a welding application. The valve <NUM> may be opened, closed, or otherwise operated by the controller <NUM> to enable, inhibit, or control gas flow (e.g., shielding gas) through the valve <NUM>. Shielding gas exits the valve <NUM> and flows through a cable <NUM> (which in some implementations may be packaged with the welding power output) to the wire feeder which provides the shielding gas to the welding application. In some examples, the power supply <NUM> does not include the gas supply <NUM>, the valve <NUM>, and/or the cable <NUM>.

In some examples, the bypass path prevention circuit <NUM> includes one or more diodes, and/or other forward voltage increase device(s), similar to the forward voltage increase circuit <NUM> of <FIG>. In such examples, the bypass path prevention circuit <NUM> is passive and is configured to increase a forward voltage from terminal <NUM> to the terminal <NUM> (e.g., in the direction of current flow).

In some other examples, the bypass path convention circuit <NUM> includes one or more switching elements such as transistors or relays. The controller <NUM> may control the bypass path prevention circuit <NUM> to enable the switching elements to conduct current when the power supply <NUM> is outputting preheating power and/or when less than a threshold weld current is detected (e.g., via a current sensor, a voltage sensor, or another sensor) as flowing between the terminals <NUM>, <NUM>. Conversely, the example controller <NUM> may control the bypass path prevention circuit <NUM> when the power supply <NUM> is not outputting preheating power and/or when more than a threshold weld current is flowing between the terminals <NUM>, <NUM>. Weld current may be detected by comparing a commanded current or voltage to be output by the power converter <NUM> with a sensed voltage with a measured current and/or voltage.

In some examples in which a transistor is used to implement the bypass path prevention circuit <NUM>, the controller <NUM> may control the transistor(s) in a linear mode, such that a voltage across the bypass path prevention circuit <NUM> is sufficient to reduce or prevent weld current from flowing through between the terminals <NUM>, <NUM> (e.g., slightly more than the driving voltage <NUM>.

While the example bypass path prevention circuit <NUM> is shown between the terminal <NUM> and the power converter <NUM>, in other examples the bypass path prevention circuit <NUM> is additionally or alternatively configured between the power converter and the terminal <NUM> to increase the forward voltage in the direction of current flow.

The present system may be realized in hardware, software, or a combination of hardware and software. The present system may be realized in a centralized fashion in at least one computing system, or in a distributed fashion where different elements are spread across several interconnected computing systems. A typical combination of hardware and software may be a general-purpose computing system with a program or other code that, when being loaded and executed, controls the computing system such that it carries out the methods described herein.

Claim 1:
A welding system (<NUM>) comprising a first contact tip (<NUM>), a preheating power supply (<NUM>), and a different welding power supply (<NUM>), wherein the different power supply (<NUM>) is connected to the first contact tip (<NUM>), the preheating power supply (<NUM>) comprising:
power conversion circuitry including first and second output power connectors (<NUM>, <NUM>) of the preheating power supply (<NUM>) wherein the first output power connector (<NUM>) is connected to a second output power connector (<NUM>) of the different power supply (<NUM>), wherein both the first and second output power connectors (<NUM>, <NUM>) are connected to the first contact tip (<NUM>), and wherein the power conversion circuitry is configured to output welding-type power to the first contact tip (<NUM>) via the first output power connector (<NUM>) and a second output power connector (<NUM>); and
a bypass path prevention circuit (<NUM>) configured to prevent less than a threshold voltage (<NUM>) applied to the first output power connector (<NUM>) and the second output power connector (<NUM>) from the different power supply (<NUM>) from causing current to flow between the first output power connector (<NUM>) and the second output power connector (<NUM>);
wherein said preheating power supply (<NUM>) establishes a preheat current path via the first contact tip (<NUM>) configured to return to the preheating power supply (<NUM>) via the second output power connector (<NUM>) of the different power supply (<NUM>).