WO2023012712A1 - Welding machine with adaptive power supply - Google Patents

Welding machine with adaptive power supply Download PDF

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Publication number
WO2023012712A1
WO2023012712A1 PCT/IB2022/057238 IB2022057238W WO2023012712A1 WO 2023012712 A1 WO2023012712 A1 WO 2023012712A1 IB 2022057238 W IB2022057238 W IB 2022057238W WO 2023012712 A1 WO2023012712 A1 WO 2023012712A1
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WO
WIPO (PCT)
Prior art keywords
power supply
phase
output
control unit
unit
Prior art date
Application number
PCT/IB2022/057238
Other languages
French (fr)
Inventor
Guglielmo De Rosa
Original Assignee
Awelco Inc. Production S.P.A.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Awelco Inc. Production S.P.A. filed Critical Awelco Inc. Production S.P.A.
Publication of WO2023012712A1 publication Critical patent/WO2023012712A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K9/00—Arc welding or cutting
    • B23K9/10—Other electric circuits therefor; Protective circuits; Remote controls
    • B23K9/1006—Power supply
    • B23K9/1043—Power supply characterised by the electric circuit

Definitions

  • the present invention concerns a welding machine with adaptive power supply, configured to automatically adapt to the input power supply so as to be capable to receive both a three-phase power supply voltage and a single-phase power supply voltage.
  • Coated electrode welding machines require a stable output voltage-current characteristic, i.e. they need to maintain a stable output current at the arc values and at the same time they need a certain flexibility on the output current values, so as to allow an operator using the welding machine to adjust its (output) welding power as desired. Therefore, such welding machines usually comprise a transformer, to allow them to be powered by the mains, that is coupled to a suitable circuit configured to reduce the voltage down to the aforementioned arc values.
  • coated electrode welding machines further comprise an electrode holder, configured to support a coated electrode that is selected from various commercially available specimens.
  • the coated electrodes are produced in various sizes and dimensions and with different functions, on the basis of safety and/or operability needs.
  • the object of the present invention is therefore to allow in a simple, reliable, efficient, rapid, versatile and inexpensive way to carry out an arc and/or coated electrode welding.
  • a welding machine with adaptive power supply configured to automatically adapt to the input power supply alternatively selected between a three-phase power supply voltage and a single-phase power supply voltage, comprising an internal circuitry comprising: an input interface, comprising at least one input connector configured to be connected to a mains power supply, wherein the input interface comprises three output phase cables, a neutral wire, and a circuit ground wire, and wherein: o when said mains power supply has three-phase voltage, said three phase cables of the input interface are configured to be connected to respective phase cables of said mains power supply, and o when said mains power supply has single-phase voltage, said three phase cables of the input interface are configured to be short-circuited and connected to the phase cable of said mains power supply and said neutral cable of the input interface is configured to be connected to the neutral cable of said mains power supply; a detection unit connected to the three phase cables and to the neutral cable of the input interface and configured to detect whether said mains power supply has three-phase voltage or single-phase voltage
  • said detection unit may comprise: a first transformer, the primary winding of which is connected to said two cables selected from the three phase cables of the input interface; a second transformer, the primary winding of which is connected to said cable selected from the three phase cables of the input interface and to said neutral cable of the input interface; a first rectifier circuit connected to the secondary winding of said first transformer and having a positive output and a negative output, wherein the positive output is connected to a phase terminal of the control unit; a second rectifier circuit connected to the secondary winding of said second transformer and having a positive output and a negative output, wherein the positive output is connected to a neutral terminal of the control unit; a stabiliser circuit configured to power said control unit, having o an input terminal, that is connected to the positive output of the first rectifier circuit and to the positive output of the second rectifier circuit, and o an output terminal, that is connected to a power supply terminal of the control unit; wherein said detection unit is configured to generate: said first detection signal on the positive output of the first rectifier
  • the input terminal of the stabiliser circuit may be connected to the positive output of the first rectifier circuit through at least one respective diode and/or to the positive output of the second rectifier circuit through at least one respective diode.
  • said rectifier circuit may further include a precharge relay located: at the ends of said at least one connection resistor, and at the ends of at least one auxiliary resistor connected between the first output terminal of the three-phase rectifier device and the first end node of said series connection of said two electrical charge storage devices, wherein the control unit is configured to control said precharge relay to short-circuit said at least one connection resistor and said at least one auxiliary resistor after a precharge period subsequent to reception of said first detection signal or said second detection signal by the control unit.
  • a precharge relay located: at the ends of said at least one connection resistor, and at the ends of at least one auxiliary resistor connected between the first output terminal of the three-phase rectifier device and the first end node of said series connection of said two electrical charge storage devices, wherein the control unit is configured to control said precharge relay to short-circuit said at least one connection resistor and said at least one auxiliary resistor after a precharge period subsequent to reception of said first detection signal or said second detection signal by the control unit.
  • said power unit may further comprise a power circuit that includes a plurality of semiconductor power switches, wherein said power circuit is driven by a driving circuit and powered by said rectifier circuit, wherein said driving circuit is controlled by the control unit.
  • said plurality of semiconductor power switches of the power circuit may include one or more IGBTs or may consist of a plurality of IGBTs.
  • the welding machine may further comprise at least one current sensor configured to detect a value of output current delivered by the output unit and to transmit said detected current value to said control unit, wherein said control unit dynamically controls the power unit on the basis of said detected current value.
  • the welding machine may further comprise at least one temperature sensor configured to detect a temperature of said power unit and to transmit said detected temperature to said control unit.
  • the welding machine may further comprise at least one ventilation unit configured to be controlled by said control unit and to cause the internal temperature of the welding machine to decrease, wherein when said detected temperature is higher than a predetermined threshold, said control unit activates the ventilation unit.
  • said predetermined threshold may be adjustable.
  • the ventilation unit may comprise at least one ventilation element configured to be powered by an autotransformer, a first power supply relay configured to power the autotransformer and a second power supply relay configured to power the autotransformer, wherein the autotransformer has a first end node connected to a first cable of said three phase cables of the input interface, an intermediate node connected to the first power supply relay, and a second end node connected to the second secondo power supply relay, wherein the first power supply relay is further connected to said neutral cable of the input interface, wherein the second power supply relay is further connected to a second cable of said three phase cables of the input interface different from said first cable, wherein, when said detected temperature is higher than a predetermined threshold, said control unit: when said mains power supply has three-phase voltage, activates the second power supply relay, and when said mains power supply has single-phase voltage, activates the first power supply relay.
  • the welding machine may further comprise a user interface that includes one or more selection devices configured to select a value of said output current supplied by said output unit, wherein said user interface is connected to the control unit that is configured to control said power unit on the basis of a selected value of said output current supplied by said output unit.
  • said one or more selection devices may be selected from the group comprising one or more setting potentiometers, one or more dip-switches, and a keyboard.
  • the welding machine may further comprise at least one display, connected to said control unit, and configured to display one or more elements.
  • said one or more elements may be selected from the group comprising or consisting of un currently delivered output current value, a voltage value currently present on the positive and negative output terminals of the welding machine, an internal and/or external temperature value, a type of power supply detected at the input between single-phase voltage power supply and three-phase voltage power supply.
  • the advantages offered by the welding machine with adaptive power supply according to the invention are numerous. First of all, it allows correct operation with both a three-phase and a single-phase power supply voltage, including a limited circuitry and without requiring a preliminary power supply selection intervention by an operator.
  • some embodiments of the invention allow a simple, rapid and convenient connection to the power supply voltage, presenting a single connector.
  • some embodiments of the invention allow to avoid overheating of the internal circuitry.
  • Figure 1 shows a schematic view of the internal circuit diagram of a preferred embodiment of the welding machine with adaptive power supply according to the invention, configured to operate with a three-phase power supply voltage;
  • Figure 2 shows a schematic view of the internal circuit diagram of the preferred embodiment of the welding machine with adaptive power supply of Figure 1, configured to operate with a single-phase power supply voltage.
  • the input interface 105 is configured to be connected to the mains.
  • it comprises or consists of an input connector, that is configured to be connected to both a singlephase power supply voltage and a three-phase power supply voltage, allowing the user a simple, quick, versatile and convenient connection to the mains.
  • Such input connector has at its output the phase cables R, S and T, the neutral cable N, and a circuit ground wire G.
  • a mains power supply 200 with three-phase power supply voltage e.g. 380 V
  • the input connector has the three phase cables R, S and T connected to and thus powered by the homologous mains cables RM, SM and TM while the neutral cable N is not powered.
  • a mains power supply 300 with a single-phase power supply voltage e.g.
  • further embodiments of the welding machine with adaptive power supply according to the invention may have an input interface comprising two input connectors, respectively configured to be connected to a single-phase and a three-phase power supply voltage.
  • the internal circuitry 100 of the preferred embodiment of the welding machine with adaptive power supply according to the invention further comprises a detection unit 110.
  • Such detection unit 110 comprises a first transformer T2, a second transformer Tl, a first rectifier circuit B2, a second rectifier circuit Bl and a stabiliser circuit STI, and it is configured to activate in alternative ways depending on the type of the input power supply voltage, as better described below.
  • the primary winding of the first transformer T2 receives the phase cables S and T at its input, while the secondary winding of the same first transformer T2 is connected to the first rectifier circuit B2. Therefore, the first transformer T2 is powered only in the case where the connector of the input interface 105 is connected to a mains power supply 200 with three-phase power supply voltage, as shown in Figure 1. In fact, when the connector of the input interface 105 is connected to a single-phase power supply voltage, the phase cables S and T are powered by the same phase PHI, thereby no current flows in the primary winding of the first transformer T2.
  • the first rectifier circuit B2 is configured to rectify the output voltage of the first transformer T2, providing a rectified voltage across the output positive terminal and the output negative terminal, that is connected to circuit ground.
  • the output positive terminal of the first rectifier circuit B2 is connected to both the control unit 130 and, through a diode DI, the input terminal of the stabiliser circuit STI.
  • the primary winding of the second transformer Tl receives the phase cable T and the neutral cable N at its input, while the secondary winding of the same second transformer Tl is connected to the second rectifier circuit Bl. Therefore, the second transformer Tl is powered only in the case where the connector of the input interface 105 is connected to a mains power supply 300 with single-phase supply voltage, as shown in Figure 2. In fact, when the connector of the input interface 105 is connected to a three-phase power supply voltage, the neutral cable N is not powered, thereby no current flows in the primary winding of the second transformer Tl.
  • the second rectifier circuit Bl is configured to rectify the output voltage of the second transformer Tl, providing a rectified voltage across the output positive terminal and the output negative terminal, that is connected to circuit ground.
  • the output positive terminal of the second rectifier circuit Bl is connected to both the control unit 130 and, through a diode D2, the input terminal of the stabiliser circuit STI.
  • the detection unit 110 is configured to generate a first detection signal on the positive output of the first rectifier circuit B2 and a second detection signal on the positive output of the second rectifier circuit Bl.
  • the stabiliser circuit STI is configured to receive on an input terminal in and to stabilise:
  • the voltage rectified by the first rectifier circuit B2 i.e. the voltage across the output positive terminal and the output negative terminal - that is connected to circuit ground - of the first rectifier circuit B2
  • the input connector is connected to a three-phase power supply voltage
  • the voltage rectified by the second rectifier circuit Bl i.e. the voltage across the output positive terminal and the output negative terminal - that is connected to circuit ground - of the output of the second rectifier circuit Bl
  • the input connector is connected to a single-phase power supply voltage
  • the stabiliser circuit STI further has a conventional ground terminal gnd, that is connected to circuit ground, and an output terminal out, connected to the control unit 130.
  • the output voltage of the stabiliser circuit STI (supplied through the output terminal out) is used to power the control unit 130, and all the electronic components controlling the operation of the electrical circuitry of the machine according to the invention.
  • the detection unit 110 connected to the three phase cables R, S and T and to the neutral cable N of the input interface 105, is configured to detect if the mains power supply 200 or 300 has three-phase or single-phase voltage on the basis of a first voltage present between two cables selected from the three phase cables R, S and T of the input interface 105 and of a second voltage present between a cable selected from the three phase cables R, S and T of the input interface 105 and the neutral cable N of the input interface 105.
  • the primary winding of the first transformer T2 can receive two cables selected from the three phase cables R, S and T of the input interface 105
  • the primary winding of the second transformer T1 can receive a cable selected from the three phase cables R, S and T of the input interface 105 and the neutral cable N of the input interface 105.
  • the internal circuitry 100 of the preferred embodiment of the welding machine with adaptive power supply according to the invention further comprises a control unit 130, that comprises at least one processing unit, such as a microprocessor, provided with at least one memory (not shown in Figures 1 and 2).
  • a control unit 130 that comprises at least one processing unit, such as a microprocessor, provided with at least one memory (not shown in Figures 1 and 2).
  • control unit 130 is connected to the detection unit 110, to the power unit 140, and to a plurality of sensors from which it receives a respective plurality of detections of electrical quantities characteristic of the operation of the welding machine with adaptive power supply according to the invention. Also, the control unit 130 conventionally comprises a ground terminal GP, connected to circuit ground.
  • control unit 130 is connected to the detection unit 110 through the following three terminals: a power supply terminal V, that is connected to the output terminal out of the stabiliser circuit STI, the output voltage of which (i.e. the voltage present across the terminals out and gnd - connected to circuit ground - of the stabiliser circuit STI) powers the same control unit 130; a phase terminal F, connected to the output positive terminal of the first rectifier circuit B2; and a neutral terminal E, connected to the output positive terminal of the second rectifier circuit Bl.
  • a power supply terminal V that is connected to the output terminal out of the stabiliser circuit STI, the output voltage of which (i.e. the voltage present across the terminals out and gnd - connected to circuit ground - of the stabiliser circuit STI) powers the same control unit 130
  • phase terminal F connected to the output positive terminal of the first rectifier circuit B2
  • a neutral terminal E connected to the output positive terminal of the second rectifier circuit Bl.
  • the control unit 130 is configured to detect the type of power supply to which the input interface 105 of the welding machine with adaptive power supply is connected, by monitoring the phase terminal F and the neutral terminal E.
  • the control unit 130 recognises that the welding machine with adaptive power supply is currently powered by a mains power supply 200 with three-phase power supply voltage.
  • the control unit 130 recognises that the welding machine with adaptive power supply is currently powered by a mains power supply 300 with single-phase power supply voltage.
  • control unit 130 is further connected to the power unit 140 through two driver terminals Pl and P2, i.e. two terminals connected to a driving circuit DRV1 of the power unit 140 through which the control unit 130 is configured to control a driving circuit DRV1. Also, such control unit 130 further controls a plurality of relays through a plurality of respective relay terminals, as described below.
  • control unit 130 is connected (through two terminals Hl and H2) to a temperature sensor TH1, located in proximity to the power unit 140 and configured to measure the temperature thereof and transmit it to the control unit 130.
  • a temperature sensor TH1 located in proximity to the power unit 140 and configured to measure the temperature thereof and transmit it to the control unit 130.
  • control unit 130 is further connected (through two terminals SI and S2) to a current sensor SCI of the output unit 180, configured to detect an output current delivered by the output unit 180.
  • control units comprising or consisting of one or more processing units selected from the group comprising microprocessors, processors and microcontrollers.
  • the internal circuitry 100 of the preferred embodiment of such machine further comprises a power unit 140, that is configured to supply, starting from the input power supply voltage, an AC voltage and an AC current to the output unit 180 which are configured to generate, through the output unit 180, an output DC current corresponding to the value selected by the user, as better described below.
  • a power unit 140 is connected to the input interface 105 and, as mentioned, to the output unit 180, and it comprises a rectifier circuit B3, Cl and C2 configured to power an IGBT power circuit 11, 12, 13, 14 driven by the driving circuit DRVl.
  • the rectifier circuit comprises a three-phase rectifier device B3, that can be advantageously implemented through a diode bridge, an auxiliary resistor R6 and a connecting resistor R7, two electrical charge storage devices, namely two capacitors Cl and C2 connected in series to each other, the precharge relay RL1 and the control relay RL4, and it is configured to receive at its input the single-phase or three-phase power supply voltage that is supplied by the output of the input connector of the input interface 105, and to present a voltage correctly rectified and usable by the IGBT power circuit 11, 12, 13, 14.
  • the three-phase rectifier device B3 is connected to the three phase cables R, S and T at the output of the input connector of the input interface 105, and it is configured to rectify the input single-phase or three-phase voltage.
  • a three-phase rectifier device B3 is a three-phase power supply bridge that includes six diodes arranged along three branches in parallel, each one of which includes a pair of diodes connected in series (i.e., with the same orientation of anode and cathode, whereby the cathode of a first diode of the pair is short-circuited to the anode of the second diode of the pair), wherein the connection node between the diodes of each one of the three branches is short-circuited to a respective cable of the three phase R, S and T.
  • Capacitors Cl and C2 are connected in series to each other and between the terminals of the three-phase rectifier B3.
  • the auxiliary resistor R6 is connected between the node of the anodes of the diodes of the three branches of the three-phase rectifier device B3 and the negative terminal of the series connection of the capacitors Cl and C2 (namely the terminal corresponding to the second capacitor C2).
  • the connection resistor R7 is connected between the common intermediate node of the capacitors Cl and C2 and the terminal of the control relay RL4 that is in turn connected to the neutral cable N of the input interface 105.
  • the control unit 130 is configured to control the precharge relay RL1 and the control relay RL4 to which it is connected through two relay control terminals RT1 and RT4.
  • the precharge relay RL1 is a double pole single throw (DPST) relay located at the ends of the auxiliary resistor R6 and of the connection resistor R7 and, when activated, it is configured to short-circuit the auxiliary resistor R6 and the connection resistor R7.
  • the control relay RL4 is a single pole single throw (SPST) relay that, when activated, is configured to connect the neutral cable N of the input interface 105 to the common intermediate node of the series connection of capacitors Cl and C2, through the connection resistor R7, as better described below.
  • the IGBT power circuit includes four IGBTs (Insulated Gate Bipolar Transistors) 11, 12, 13 and 14 the gate terminals of which are controlled, through respective resistors Rl, R2, R3 and R4, by respective outputs, namely DR1, DR2, DR3 and DR4, of the driving circuit DRVl.
  • IGBTs Insulated Gate Bipolar Transistors
  • the collectors of the IGBTs 11 and 14 are short-circuited to the positive terminal of the series of capacitors Cl and C2 (namely the terminal corresponding to the first capacitor Cl) and, consequently, to the node of the cathodes of the diodes of the three branches of the three-phase rectifier device B3, the respective emitters of IGBTs 11 and 14 are connected to the collectors of IGBTs 12 and 13, and the emitters of IGBTs 12 and 13 are connected to the negative terminal of the series of capacitors Cl and C2.
  • the driving circuit DRVl comprises two input terminals CT1 and CT2 connected to the driver terminals Pl and P2 of the control unit 130, and four output terminals DR1, DR2, DR3 and DR4, respectively connected to the gate terminals of the four IGBTs 11, 12, 13 and 14, through respective resistors Rl, R2, R3 and R4.
  • the output of the power unit 140 is taken in the two intermediate nodes of the connections between the two pairs of IGBTs, respectively the pair of IGBTs 11 and 12 and the pair of IGBTs 13 and 14; in other words, a first output terminal consists of the common node between the emitter of the IGBT 11 and the collector of the IGBT 12, and a second output terminal consists of the common node between the emitter of the IGBT 14 and the collector of the IGBT 13.
  • Such output terminals of the power unit 140 are connected to the ends of the primary winding of a transformer T3 forming the input of the output unit 180.
  • further embodiments of the welding machine with adaptive power supply according to the invention may comprise power units comprising a number other than four of IGBTs, for example six or eight, and/or semiconductor power switches different from IGBTs, such as for example semiconductor power switches selected from the group comprising or consisting of IGBTs, MOSFETs, SCRs, TRIACs and BJTs , and/or circuit configurations of power stages different from that illustrated, such as Forward and/or Full Bridge and/or Phase Shift.
  • the internal circuitry 100 of the preferred embodiment of such machine further comprises the output unit 180, that comprises the transformer T3, two diodes D3 and D4, and an output inductor LI.
  • the output unit 180 is configured to provide the output current and voltage of the welding machine with adaptive power supply.
  • the voltage present at the secondary winding of the transformer T3 is rectified through the diodes D3 and D4, each one of which has the anode connected to a respective terminal of the secondary winding of the transformer T3, while the cathodes of the diodes D3 and D4 are short-circuited together.
  • the output inductor LI is connected between the cathodes of diodes D3 and D4 and the positive output terminal 01 of the machine according to the invention, while the central node of the secondary winding of the transformer T3 is connected to the negative output terminal 02 of the machine according to the invention.
  • the output inductor LI is configured to deliver the current, advantageously selected by the user through a user interface, being connected to the positive output terminal 01 of the welding machine.
  • the output unit 180 further comprises a current sensor SCI, configured to measure the value of the current delivered at the output, and to transmit such value to the control unit 130 through the two sensor terminals SI and S2.
  • a current sensor SCI configured to measure the value of the current delivered at the output, and to transmit such value to the control unit 130 through the two sensor terminals SI and S2.
  • further embodiments of the welding machine with adaptive power supply according to the invention may comprise output units further comprising one or more elements selected from the group comprising current sensors, voltage sensors, temperature sensors and humidity sensors.
  • the welding machine with adaptive power supply further comprises a user interface (not shown in the attached figures).
  • a user interface comprises means for selecting the desired value of output current, such as for example one or more setting potentiometers and/or one or more dip-switches and/or a keyboard, connected to the control unit 130.
  • control unit 130 is configured to read the desired output current value set by the user through such user interface and to consequently drive the driving circuit DRV1 through the driver terminals Pl and P2.
  • control unit 130 is advantageously configured to control and supervise the current delivered at the output through the current sensor SCI, advantageously allowing a dynamic adjustment of the driving circuit DRVl.
  • the user interface may further advantageously comprise at least one display, connected to the control unit 130 and configured to show to the user one or more elements selected from the group comprising or consisting of a value of current selected by the user, a value of current currently delivered, a value of voltage currently present at the output positive and negative terminals 01 and 02 of the welding machine, an internal and/or external temperature value, the type of power supply detected at the input (i.e. single-phase or three-phase), the maximum settable value of current.
  • the first transformer T2 of the detection unit 110 is powered and consequently the detection unit 110 generates a first detection signal at the positive output of the first rectifier circuit B2, while the second transformer T1 of the same detection unit 110 is not powered.
  • control unit 130 detects the presence of a voltage across the phase terminal F and the ground terminal GP, i.e. it receives a first power supply signal from the detection unit 110, and verifies the absence of voltage across the neutral terminal E and the ground terminal GP, detecting that the welding machine with adaptive power supply is currently powered by three-phase voltage.
  • the common intermediate node of the series connection of the two capacitors is floating, i.e. such common intermediate node is connected only to two internal ends of the series connection of the two capacitors Cl and C2.
  • the control unit 130 supervises the precharge of the capacitors Cl and C2, that takes place through the auxiliary resistor R6 until the control unit 130 activates the precharge relay RL1 after a time ranging from 1 to 3 seconds, optionally equal to 2 seconds, and consequently short-circuiting the auxiliary resistor R6.
  • the control unit 130 sets the maximum value of current that can be delivered at the output terminals 01 and 02.
  • the control unit 130 reads the desired output current value set by the user through the user interface, and consequently it sets the driving circuit DRVl through the driver terminals Pl and P2.
  • the driving circuit DRV1 in turn supplies at the output the signals driving the gates of the IGBTs 11, 12 13 and 14 corresponding to the instructions received from the control unit 130, whereby the four IGBTs 11, 12, 13 and 14 are driven so as to supply at the primary winding of the transformer T3 of the output unit 180 AC voltage and current configured to generate, through the output unit 180, the DC output current corresponding to the value selected by the user.
  • the output unit 180 rectifies the voltage present at the secondary winding of the transformer T3, received by the power unit 140, and outputs the current selected by the user through the inductor LI and the output terminals 01 and 02.
  • the control unit 130 controls and supervises the current delivered at the output through the current sensor SCI.
  • the second transformer T1 of the detection unit 110 is powered and consequently the detection unit 110 generates a second detection signal at the positive output of the second rectifier circuit Bl, while the first transformer T2 of the same detection unit 110 is not powered.
  • control unit 130 detects the presence of a voltage across the neutral terminal E and the ground terminal GP, i.e. it receives a second power supply signal from the detection unit 110, and verifies the absence of voltage across the phase terminal F and the ground terminal GP, detecting that the welding machine with adaptive power supply is currently powered by single-phase voltage.
  • control unit 130 activates the control relay RL4, connecting the neutral cable N of the input interface 105 to the common intermediate node of the series connection of the capacitors Cl and C2, through the connection resistor R7, and then the control unit 130 supervises the precharge of the capacitors Cl and C2, that takes place through the auxiliary resistor R6 and the connection resistor R7, until the control unit 130 activates the precharge relay RL1 after a time ranging from 1 to 3 seconds, optionally equal to 2 seconds, consequently short-circuiting the auxiliary resistor R6 and the connection resistor R7.
  • the single-phase voltage rectified through the three-phase rectifier device B3 will be present at the series of capacitors Cl and C2.
  • control unit 130 sets the maximum value of current that can be delivered at the output terminals 01 and 02; this value is lower than the one set in the case where the welding machine is powered by a three-phase voltage. Subsequently, the control unit 130 reads the desired output current value set by the user through the user interface, and consequently it sets the driving circuit DRV1 through the driver terminals Pl and P2.
  • the driving circuit DRV1 in turn supplies at the output the signals driving the gates of the IGBTs 11, 12 13 and 14 corresponding to the instructions received from the control unit 130, whereby the four IGBTs 11, 12, 13 and 14 are driven so as to supply at the primary winding of the transformer T3 of the output unit 180 an AC voltage and current configured to generate, through the output unit 180, the DC output current corresponding to the value selected by the user.
  • the output unit 180 rectifies the voltage present on the secondary winding of the transformer T3, received by the power unit 140, and outputs the current selected by the user through the inductor LI and the output terminals 01 and 02.
  • the control unit 130 controls and supervises the current delivered at the output through the current sensor SCI.
  • the internal circuitry 100 of the preferred embodiment of the welding machine with adaptive power supply also comprises a ventilation unit 160, configured to cause the internal temperature of the welding machine to decrease and comprising at least one ventilation element 165, an autotransformer T4, a first relay RL2 for powering the autotransformer T4 and a second relay RL5 for powering the autotransformer T4 (which are advantageously SPST relays).
  • the at least one ventilation element 165 advantageously comprises at least one fan.
  • the ventilation unit 160 is controlled by the control unit 130 through the first relay RL2 for powering the autotransformer T4 and the second relay RL5 for powering the autotransformer T4, which are connected to the control unit 130 through two respective relay terminals RT2 and RT5.
  • the second relay RL5 for powering the autotransformer T4 when activated, connects respective ends of the autotransformer T4 to the phase cable S and to the phase cable T.
  • Such second relay RL5 for powering the autotransformer T4 can connect, when activated, respective ends of the autotransformerT4 to two cables selected from the three phase cables R, S and T.
  • the first relay RL2 for powering the autotransformer T4 when activated, connects respective ends of the autotransformerT4 to the phase cable S and to the neutral cable N.
  • Such first relay RL2 for powering the autotransformer T4 can connect, when activated, respective ends of the autotransformer T4 to the neutral cable N and to a cable selected between the three phase cables R, S and T.
  • the autotransformer T4 has a first end node connected to a first cable selected from the three phase cables R, S, and T of the input interface 105, an intermediate node connected to the first relay RL2 for powering the autotransformer T4, and a second end node connected to the second relay RL5 for powering the autotransformer T4.
  • the autotransformer T4 is connected to the input of the at least one ventilation element 165 and is configured to supply it with an appropriate voltage to allow it to operate correctly.
  • control unit 130 When the control unit 130 detects, through the temperature sensor TH1, an internal temperature higher than a predetermined, optionally adjustable, threshold, it activates the ventilation unit 160. In particular, in the case where the control unit 130 has detected an input three-phase power supply, it activates the second relay RL5 for powering the autotransformer T4 (as shown in Figure 1), whereby the voltage present between the phase cables S and T is applied across the autotransformer T4 that consequently powers said at least one ventilation element 165.
  • control unit 130 activates the first relay RL2 for powering the autotransformer T4 (as shown in Figure 2), whereby the voltage present between the phase cable S and the neutral cable N is applied to the autotransformer T4 that consequently powers said at least one ventilation element 165.
  • the at least one display of the user interface is further configured to show to the user also the possible activation status of the ventilation unit 160.

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Abstract

Welding machine with adaptive power supply, configured to be powered by a three-phase power supply voltage or a single-phase power supply voltage, comprising an internal circuitry (100) comprising: - an input interface (105); - a power supply voltage type detection unit (110); - a control unit (130); - a power unit (140); and - an output unit (180); wherein said control unit (130) is configured to determine the type of power supply voltage currently present at the input, namely: - three-phase voltage; - single-phase voltage.

Description

WELDING MACHINE WITH ADAPTIVE POWER SUPPLY
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The present invention concerns a welding machine with adaptive power supply, configured to automatically adapt to the input power supply so as to be capable to receive both a three-phase power supply voltage and a single-phase power supply voltage.
In the welding field, the use of fixed or portable electric welding machines is known. In particular, arc and coated electrode welding are some of the most widespread techniques, since they are suitable for use in open or closed environments, and at the same time they require low- cost welding machines.
Coated electrode welding machines require a stable output voltage-current characteristic, i.e. they need to maintain a stable output current at the arc values and at the same time they need a certain flexibility on the output current values, so as to allow an operator using the welding machine to adjust its (output) welding power as desired. Therefore, such welding machines usually comprise a transformer, to allow them to be powered by the mains, that is coupled to a suitable circuit configured to reduce the voltage down to the aforementioned arc values.
Also, coated electrode welding machines further comprise an electrode holder, configured to support a coated electrode that is selected from various commercially available specimens. The coated electrodes are produced in various sizes and dimensions and with different functions, on the basis of safety and/or operability needs.
Considering the variety of environments where it is necessary to carry out a welding process (e.g. open environments such as construction sites, closed environments such as laboratories), there is a need for a welding machine with high versatility of use, i.e. that is capable of to operate correctly with both three-phase and single-phase power supply voltage.
Documents JP2016140885A, CN201035350Y and CN205111022U, although disclosing welding machines suitable for operating with both a three-phase and single-phase power supply voltage, suffer from some drawbacks on the one hand concerning an overabundance of circuitry to be activated selectively, and on the other hand concerning techniques of detection that tend to dissipate excessive power, being mostly linked to voltage dividers.
Thus, there is a need in the field for a welding machine having a high versatility of application, that can be used in a simple, reliable, efficient and rapid way with both three-phase and single-phase power supply. The object of the present invention is therefore to allow in a simple, reliable, efficient, rapid, versatile and inexpensive way to carry out an arc and/or coated electrode welding.
It is specific subject-matter of the present invention a welding machine with adaptive power supply, configured to automatically adapt to the input power supply alternatively selected between a three-phase power supply voltage and a single-phase power supply voltage, comprising an internal circuitry comprising: an input interface, comprising at least one input connector configured to be connected to a mains power supply, wherein the input interface comprises three output phase cables, a neutral wire, and a circuit ground wire, and wherein: o when said mains power supply has three-phase voltage, said three phase cables of the input interface are configured to be connected to respective phase cables of said mains power supply, and o when said mains power supply has single-phase voltage, said three phase cables of the input interface are configured to be short-circuited and connected to the phase cable of said mains power supply and said neutral cable of the input interface is configured to be connected to the neutral cable of said mains power supply; a detection unit connected to the three phase cables and to the neutral cable of the input interface and configured to detect whether said mains power supply has three-phase voltage or single-phase voltage on the basis of a first voltage present between two cables selected from the three phase cables of the input interface and of a second voltage present between a cable selected from the three phase cables of the input interface and the neutral cable of the input interface; a control unit connected to the detection unit; a power unit controlled by the control unit connected to the input interface and to an output unit, wherein the power unit comprises a rectifier circuit that includes a three-phase rectifier device connected to said three phase cables of the input interface, the three-phase rectifier device having a first output terminal and a second output terminal which are respectively connected to a first end node and a second end node of a series connection of two electrical charge storage devices having a common intermediate node, and an output unit configured to provide an output current and an output voltage at an output positive terminal and an output negative terminal of the welding machine with adaptive power supply; wherein the control unit is configured to control the power unit through a control relay connected between the neutral cable of the input interface and said common intermediate node wherein: when the control unit receives from the detection unit a first detection signal indicating that said mains power supply has three-phase voltage, said common intermediate node is floating, and when the control unit receives from the detection unit a second detection signal indicating that said mains power supply has single-phase voltage, said common intermediate node is connected to the neutral cable of the input interface through at least one connection resistor.
According to another aspect of the invention, said detection unit may comprise: a first transformer, the primary winding of which is connected to said two cables selected from the three phase cables of the input interface; a second transformer, the primary winding of which is connected to said cable selected from the three phase cables of the input interface and to said neutral cable of the input interface; a first rectifier circuit connected to the secondary winding of said first transformer and having a positive output and a negative output, wherein the positive output is connected to a phase terminal of the control unit; a second rectifier circuit connected to the secondary winding of said second transformer and having a positive output and a negative output, wherein the positive output is connected to a neutral terminal of the control unit; a stabiliser circuit configured to power said control unit, having o an input terminal, that is connected to the positive output of the first rectifier circuit and to the positive output of the second rectifier circuit, and o an output terminal, that is connected to a power supply terminal of the control unit; wherein said detection unit is configured to generate: said first detection signal on the positive output of the first rectifier circuit; and said second detection signal on the positive output of the second rectifier circuit.
According to an additional aspect of the invention, the input terminal of the stabiliser circuit may be connected to the positive output of the first rectifier circuit through at least one respective diode and/or to the positive output of the second rectifier circuit through at least one respective diode.
According to a further aspect of the invention, said rectifier circuit may further include a precharge relay located: at the ends of said at least one connection resistor, and at the ends of at least one auxiliary resistor connected between the first output terminal of the three-phase rectifier device and the first end node of said series connection of said two electrical charge storage devices, wherein the control unit is configured to control said precharge relay to short-circuit said at least one connection resistor and said at least one auxiliary resistor after a precharge period subsequent to reception of said first detection signal or said second detection signal by the control unit.
According to an additional aspect of the invention, said power unit may further comprise a power circuit that includes a plurality of semiconductor power switches, wherein said power circuit is driven by a driving circuit and powered by said rectifier circuit, wherein said driving circuit is controlled by the control unit.
According to a further aspect of the invention, said plurality of semiconductor power switches of the power circuit may include one or more IGBTs or may consist of a plurality of IGBTs.
According to another aspect of the invention, the welding machine may further comprise at least one current sensor configured to detect a value of output current delivered by the output unit and to transmit said detected current value to said control unit, wherein said control unit dynamically controls the power unit on the basis of said detected current value.
According to a further aspect of the invention, the welding machine may further comprise at least one temperature sensor configured to detect a temperature of said power unit and to transmit said detected temperature to said control unit.
According to an additional aspect of the invention, the welding machine may further comprise at least one ventilation unit configured to be controlled by said control unit and to cause the internal temperature of the welding machine to decrease, wherein when said detected temperature is higher than a predetermined threshold, said control unit activates the ventilation unit.
According to a further aspect of the invention, said predetermined threshold may be adjustable. According to another aspect of the invention, the ventilation unit may comprise at least one ventilation element configured to be powered by an autotransformer, a first power supply relay configured to power the autotransformer and a second power supply relay configured to power the autotransformer, wherein the autotransformer has a first end node connected to a first cable of said three phase cables of the input interface, an intermediate node connected to the first power supply relay, and a second end node connected to the second secondo power supply relay, wherein the first power supply relay is further connected to said neutral cable of the input interface, wherein the second power supply relay is further connected to a second cable of said three phase cables of the input interface different from said first cable, wherein, when said detected temperature is higher than a predetermined threshold, said control unit: when said mains power supply has three-phase voltage, activates the second power supply relay, and when said mains power supply has single-phase voltage, activates the first power supply relay.
According to a further aspect of the invention, the welding machine may further comprise a user interface that includes one or more selection devices configured to select a value of said output current supplied by said output unit, wherein said user interface is connected to the control unit that is configured to control said power unit on the basis of a selected value of said output current supplied by said output unit.
According to an additional aspect of the invention, said one or more selection devices may be selected from the group comprising one or more setting potentiometers, one or more dip-switches, and a keyboard.
According to another aspect of the invention, the welding machine may further comprise at least one display, connected to said control unit, and configured to display one or more elements.
According to a further aspect of the invention, said one or more elements may be selected from the group comprising or consisting of un currently delivered output current value, a voltage value currently present on the positive and negative output terminals of the welding machine, an internal and/or external temperature value, a type of power supply detected at the input between single-phase voltage power supply and three-phase voltage power supply.
The advantages offered by the welding machine with adaptive power supply according to the invention are numerous. First of all, it allows correct operation with both a three-phase and a single-phase power supply voltage, including a limited circuitry and without requiring a preliminary power supply selection intervention by an operator.
Furthermore, it allows to detect in a reliable and efficient way the type of power supply voltage.
Furthermore, some embodiments of the invention allow a simple, rapid and convenient connection to the power supply voltage, presenting a single connector.
In addition to this, some embodiments of the invention allow to avoid overheating of the internal circuitry.
The present invention will be now described, for illustrative but not limiting purposes, according to its preferred embodiments, with particular reference to the Figures of the attached drawings, in which:
Figure 1 shows a schematic view of the internal circuit diagram of a preferred embodiment of the welding machine with adaptive power supply according to the invention, configured to operate with a three-phase power supply voltage;
Figure 2 shows a schematic view of the internal circuit diagram of the preferred embodiment of the welding machine with adaptive power supply of Figure 1, configured to operate with a single-phase power supply voltage.
In the Figures identical reference numerals will be used for alike elements.
With reference to Figures 1 and 2, it is possible to observe the internal circuitry 100 of a preferred embodiment of the welding machine with adaptive power supply according to the invention that comprises an input interface 105, a detection unit 110, a control unit 130, a power unit 140 and an output unit 180.
The input interface 105 is configured to be connected to the mains. Advantageously, it comprises or consists of an input connector, that is configured to be connected to both a singlephase power supply voltage and a three-phase power supply voltage, allowing the user a simple, quick, versatile and convenient connection to the mains.
Such input connector has at its output the phase cables R, S and T, the neutral cable N, and a circuit ground wire G. When the input connector is connected to a mains power supply 200 with three-phase power supply voltage (e.g. 380 V), as shown in Figure 1, it has the three phase cables R, S and T connected to and thus powered by the homologous mains cables RM, SM and TM while the neutral cable N is not powered. On the contrary, in the case where the input connector is connected to a mains power supply 300 with a single-phase power supply voltage (e.g. 220 V), as shown in Figure 2, it has the three phase cables R, S and T at its output connected to and thus powered in parallel by the same phase PHI of the single-phase power supply mains 300, and the neutral cable N connected to and thus powered by the homologous mains cable NM.
It must be noted that further embodiments of the welding machine with adaptive power supply according to the invention may have an input interface comprising two input connectors, respectively configured to be connected to a single-phase and a three-phase power supply voltage.
As previously stated, the internal circuitry 100 of the preferred embodiment of the welding machine with adaptive power supply according to the invention further comprises a detection unit 110.
Such detection unit 110 comprises a first transformer T2, a second transformer Tl, a first rectifier circuit B2, a second rectifier circuit Bl and a stabiliser circuit STI, and it is configured to activate in alternative ways depending on the type of the input power supply voltage, as better described below.
The primary winding of the first transformer T2 receives the phase cables S and T at its input, while the secondary winding of the same first transformer T2 is connected to the first rectifier circuit B2. Therefore, the first transformer T2 is powered only in the case where the connector of the input interface 105 is connected to a mains power supply 200 with three-phase power supply voltage, as shown in Figure 1. In fact, when the connector of the input interface 105 is connected to a single-phase power supply voltage, the phase cables S and T are powered by the same phase PHI, thereby no current flows in the primary winding of the first transformer T2.
The first rectifier circuit B2 is configured to rectify the output voltage of the first transformer T2, providing a rectified voltage across the output positive terminal and the output negative terminal, that is connected to circuit ground.
The output positive terminal of the first rectifier circuit B2 is connected to both the control unit 130 and, through a diode DI, the input terminal of the stabiliser circuit STI.
The primary winding of the second transformer Tl receives the phase cable T and the neutral cable N at its input, while the secondary winding of the same second transformer Tl is connected to the second rectifier circuit Bl. Therefore, the second transformer Tl is powered only in the case where the connector of the input interface 105 is connected to a mains power supply 300 with single-phase supply voltage, as shown in Figure 2. In fact, when the connector of the input interface 105 is connected to a three-phase power supply voltage, the neutral cable N is not powered, thereby no current flows in the primary winding of the second transformer Tl.
The second rectifier circuit Bl is configured to rectify the output voltage of the second transformer Tl, providing a rectified voltage across the output positive terminal and the output negative terminal, that is connected to circuit ground.
The output positive terminal of the second rectifier circuit Bl is connected to both the control unit 130 and, through a diode D2, the input terminal of the stabiliser circuit STI.
The detection unit 110 is configured to generate a first detection signal on the positive output of the first rectifier circuit B2 and a second detection signal on the positive output of the second rectifier circuit Bl.
Also, the stabiliser circuit STI is configured to receive on an input terminal in and to stabilise:
- the voltage rectified by the first rectifier circuit B2 (i.e. the voltage across the output positive terminal and the output negative terminal - that is connected to circuit ground - of the first rectifier circuit B2), in the case where the input connector is connected to a three-phase power supply voltage, or alternatively
- the voltage rectified by the second rectifier circuit Bl (i.e. the voltage across the output positive terminal and the output negative terminal - that is connected to circuit ground - of the output of the second rectifier circuit Bl), in the case where the input connector is connected to a single-phase power supply voltage.
The stabiliser circuit STI further has a conventional ground terminal gnd, that is connected to circuit ground, and an output terminal out, connected to the control unit 130. The output voltage of the stabiliser circuit STI (supplied through the output terminal out) is used to power the control unit 130, and all the electronic components controlling the operation of the electrical circuitry of the machine according to the invention.
It must be noted that the detection unit 110, connected to the three phase cables R, S and T and to the neutral cable N of the input interface 105, is configured to detect if the mains power supply 200 or 300 has three-phase or single-phase voltage on the basis of a first voltage present between two cables selected from the three phase cables R, S and T of the input interface 105 and of a second voltage present between a cable selected from the three phase cables R, S and T of the input interface 105 and the neutral cable N of the input interface 105.
In other words, the primary winding of the first transformer T2 can receive two cables selected from the three phase cables R, S and T of the input interface 105, and the primary winding of the second transformer T1 can receive a cable selected from the three phase cables R, S and T of the input interface 105 and the neutral cable N of the input interface 105.
As previously stated, the internal circuitry 100 of the preferred embodiment of the welding machine with adaptive power supply according to the invention further comprises a control unit 130, that comprises at least one processing unit, such as a microprocessor, provided with at least one memory (not shown in Figures 1 and 2).
Such control unit 130 is connected to the detection unit 110, to the power unit 140, and to a plurality of sensors from which it receives a respective plurality of detections of electrical quantities characteristic of the operation of the welding machine with adaptive power supply according to the invention. Also, the control unit 130 conventionally comprises a ground terminal GP, connected to circuit ground.
More in detail, the control unit 130 is connected to the detection unit 110 through the following three terminals: a power supply terminal V, that is connected to the output terminal out of the stabiliser circuit STI, the output voltage of which (i.e. the voltage present across the terminals out and gnd - connected to circuit ground - of the stabiliser circuit STI) powers the same control unit 130; a phase terminal F, connected to the output positive terminal of the first rectifier circuit B2; and a neutral terminal E, connected to the output positive terminal of the second rectifier circuit Bl.
The control unit 130 is configured to detect the type of power supply to which the input interface 105 of the welding machine with adaptive power supply is connected, by monitoring the phase terminal F and the neutral terminal E.
In particular, when such input interface 105 is connected to a mains power supply 200 with three-phase power supply voltage, the first transformer T2 is powered, and thus a voltage across the output positive terminal of the first rectifier circuit B2 and circuit ground is present, which voltage is detected by the control unit 130 across the phase terminal F and the ground terminal GP; on the contrary, the second transformer T1 is not powered, and consequently the voltage across the output positive terminal of the second rectifier circuit Bl and circuit ground is zero, which zero voltage is verified by the control unit 130 across the neutral terminal E and the ground terminal GP. Therefore, the control unit 130 recognises that the welding machine with adaptive power supply is currently powered by a mains power supply 200 with three-phase power supply voltage.
Vice versa, when the input interface 105 is connected to a mains power supply 300 with single-phase power supply voltage, the second transformer T1 is powered, and thus a voltage across the output positive terminal of the second rectifier circuit Bl and circuit ground is present, which voltage is detected by the control unit 130 across the neutral terminal E and the ground terminal GP; on the contrary, the first transformer T2 is not powered, and consequently the voltage across the output positive terminal of the first rectifier circuit B2 and circuit ground is zero, which zero voltage is verified by the control unit 130 across the phase terminal F and the ground terminal GP. Therefore, the control unit 130 recognises that the welding machine with adaptive power supply is currently powered by a mains power supply 300 with single-phase power supply voltage.
As stated, the control unit 130 is further connected to the power unit 140 through two driver terminals Pl and P2, i.e. two terminals connected to a driving circuit DRV1 of the power unit 140 through which the control unit 130 is configured to control a driving circuit DRV1. Also, such control unit 130 further controls a plurality of relays through a plurality of respective relay terminals, as described below.
Advantageously, the control unit 130 is connected (through two terminals Hl and H2) to a temperature sensor TH1, located in proximity to the power unit 140 and configured to measure the temperature thereof and transmit it to the control unit 130.
Still advantageously, the control unit 130 is further connected (through two terminals SI and S2) to a current sensor SCI of the output unit 180, configured to detect an output current delivered by the output unit 180.
It must be noted that further embodiments of the welding machine with adaptive power supply according to the invention may comprise control units comprising or consisting of one or more processing units selected from the group comprising microprocessors, processors and microcontrollers.
Returning to the welding machine with adaptive power supply of Figures 1 and 2, the internal circuitry 100 of the preferred embodiment of such machine further comprises a power unit 140, that is configured to supply, starting from the input power supply voltage, an AC voltage and an AC current to the output unit 180 which are configured to generate, through the output unit 180, an output DC current corresponding to the value selected by the user, as better described below. Such power unit 140 is connected to the input interface 105 and, as mentioned, to the output unit 180, and it comprises a rectifier circuit B3, Cl and C2 configured to power an IGBT power circuit 11, 12, 13, 14 driven by the driving circuit DRVl.
The rectifier circuit comprises a three-phase rectifier device B3, that can be advantageously implemented through a diode bridge, an auxiliary resistor R6 and a connecting resistor R7, two electrical charge storage devices, namely two capacitors Cl and C2 connected in series to each other, the precharge relay RL1 and the control relay RL4, and it is configured to receive at its input the single-phase or three-phase power supply voltage that is supplied by the output of the input connector of the input interface 105, and to present a voltage correctly rectified and usable by the IGBT power circuit 11, 12, 13, 14.
The three-phase rectifier device B3 is connected to the three phase cables R, S and T at the output of the input connector of the input interface 105, and it is configured to rectify the input single-phase or three-phase voltage. As shown in Figures 1 and 2, such a three-phase rectifier device B3 is a three-phase power supply bridge that includes six diodes arranged along three branches in parallel, each one of which includes a pair of diodes connected in series (i.e., with the same orientation of anode and cathode, whereby the cathode of a first diode of the pair is short-circuited to the anode of the second diode of the pair), wherein the connection node between the diodes of each one of the three branches is short-circuited to a respective cable of the three phase R, S and T.
Capacitors Cl and C2 are connected in series to each other and between the terminals of the three-phase rectifier B3. The auxiliary resistor R6 is connected between the node of the anodes of the diodes of the three branches of the three-phase rectifier device B3 and the negative terminal of the series connection of the capacitors Cl and C2 (namely the terminal corresponding to the second capacitor C2). The connection resistor R7 is connected between the common intermediate node of the capacitors Cl and C2 and the terminal of the control relay RL4 that is in turn connected to the neutral cable N of the input interface 105.
The control unit 130 is configured to control the precharge relay RL1 and the control relay RL4 to which it is connected through two relay control terminals RT1 and RT4. The precharge relay RL1 is a double pole single throw (DPST) relay located at the ends of the auxiliary resistor R6 and of the connection resistor R7 and, when activated, it is configured to short-circuit the auxiliary resistor R6 and the connection resistor R7. The control relay RL4 is a single pole single throw (SPST) relay that, when activated, is configured to connect the neutral cable N of the input interface 105 to the common intermediate node of the series connection of capacitors Cl and C2, through the connection resistor R7, as better described below.
The IGBT power circuit includes four IGBTs (Insulated Gate Bipolar Transistors) 11, 12, 13 and 14 the gate terminals of which are controlled, through respective resistors Rl, R2, R3 and R4, by respective outputs, namely DR1, DR2, DR3 and DR4, of the driving circuit DRVl.
In particular, the collectors of the IGBTs 11 and 14 are short-circuited to the positive terminal of the series of capacitors Cl and C2 (namely the terminal corresponding to the first capacitor Cl) and, consequently, to the node of the cathodes of the diodes of the three branches of the three-phase rectifier device B3, the respective emitters of IGBTs 11 and 14 are connected to the collectors of IGBTs 12 and 13, and the emitters of IGBTs 12 and 13 are connected to the negative terminal of the series of capacitors Cl and C2.
As stated, the driving circuit DRVl comprises two input terminals CT1 and CT2 connected to the driver terminals Pl and P2 of the control unit 130, and four output terminals DR1, DR2, DR3 and DR4, respectively connected to the gate terminals of the four IGBTs 11, 12, 13 and 14, through respective resistors Rl, R2, R3 and R4.
The output of the power unit 140 is taken in the two intermediate nodes of the connections between the two pairs of IGBTs, respectively the pair of IGBTs 11 and 12 and the pair of IGBTs 13 and 14; in other words, a first output terminal consists of the common node between the emitter of the IGBT 11 and the collector of the IGBT 12, and a second output terminal consists of the common node between the emitter of the IGBT 14 and the collector of the IGBT 13. Such output terminals of the power unit 140 are connected to the ends of the primary winding of a transformer T3 forming the input of the output unit 180.
It must be noted that further embodiments of the welding machine with adaptive power supply according to the invention may comprise power units comprising a number other than four of IGBTs, for example six or eight, and/or semiconductor power switches different from IGBTs, such as for example semiconductor power switches selected from the group comprising or consisting of IGBTs, MOSFETs, SCRs, TRIACs and BJTs , and/or circuit configurations of power stages different from that illustrated, such as Forward and/or Full Bridge and/or Phase Shift. Returning to the welding machine with adaptive power supply of Figures 1 and 2, the internal circuitry 100 of the preferred embodiment of such machine further comprises the output unit 180, that comprises the transformer T3, two diodes D3 and D4, and an output inductor LI.
The output unit 180 is configured to provide the output current and voltage of the welding machine with adaptive power supply. The voltage present at the secondary winding of the transformer T3 is rectified through the diodes D3 and D4, each one of which has the anode connected to a respective terminal of the secondary winding of the transformer T3, while the cathodes of the diodes D3 and D4 are short-circuited together. The output inductor LI is connected between the cathodes of diodes D3 and D4 and the positive output terminal 01 of the machine according to the invention, while the central node of the secondary winding of the transformer T3 is connected to the negative output terminal 02 of the machine according to the invention. The output inductor LI is configured to deliver the current, advantageously selected by the user through a user interface, being connected to the positive output terminal 01 of the welding machine.
Advantageously, the output unit 180 further comprises a current sensor SCI, configured to measure the value of the current delivered at the output, and to transmit such value to the control unit 130 through the two sensor terminals SI and S2.
It must be noted that further embodiments of the welding machine with adaptive power supply according to the invention may comprise output units further comprising one or more elements selected from the group comprising current sensors, voltage sensors, temperature sensors and humidity sensors.
The welding machine with adaptive power supply according to the invention further comprises a user interface (not shown in the attached figures). Such user interface comprises means for selecting the desired value of output current, such as for example one or more setting potentiometers and/or one or more dip-switches and/or a keyboard, connected to the control unit 130.
In this way, the control unit 130 is configured to read the desired output current value set by the user through such user interface and to consequently drive the driving circuit DRV1 through the driver terminals Pl and P2.
Moreover, the control unit 130 is advantageously configured to control and supervise the current delivered at the output through the current sensor SCI, advantageously allowing a dynamic adjustment of the driving circuit DRVl.
The user interface may further advantageously comprise at least one display, connected to the control unit 130 and configured to show to the user one or more elements selected from the group comprising or consisting of a value of current selected by the user, a value of current currently delivered, a value of voltage currently present at the output positive and negative terminals 01 and 02 of the welding machine, an internal and/or external temperature value, the type of power supply detected at the input (i.e. single-phase or three-phase), the maximum settable value of current.
In the following, the operation of the welding machine with adaptive power supply according to the invention will be described in detail, initially in the case where it is powered by a three-phase power supply voltage and subsequently in the case where it is powered by a single-phase power supply voltage.
As previously stated, when the welding machine with adaptive power supply is connected to a three-phase power supply voltage, the first transformer T2 of the detection unit 110 is powered and consequently the detection unit 110 generates a first detection signal at the positive output of the first rectifier circuit B2, while the second transformer T1 of the same detection unit 110 is not powered.
Therefore, the control unit 130 detects the presence of a voltage across the phase terminal F and the ground terminal GP, i.e. it receives a first power supply signal from the detection unit 110, and verifies the absence of voltage across the neutral terminal E and the ground terminal GP, detecting that the welding machine with adaptive power supply is currently powered by three-phase voltage. At this point, the common intermediate node of the series connection of the two capacitors is floating, i.e. such common intermediate node is connected only to two internal ends of the series connection of the two capacitors Cl and C2. The control unit 130 supervises the precharge of the capacitors Cl and C2, that takes place through the auxiliary resistor R6 until the control unit 130 activates the precharge relay RL1 after a time ranging from 1 to 3 seconds, optionally equal to 2 seconds, and consequently short-circuiting the auxiliary resistor R6. Thus, the three-phase voltage rectified through the three-phase rectifier device B3 will be present at the series of capacitors Cl and C2. At the same time, the control unit 130 sets the maximum value of current that can be delivered at the output terminals 01 and 02. Subsequently, the control unit 130 reads the desired output current value set by the user through the user interface, and consequently it sets the driving circuit DRVl through the driver terminals Pl and P2. The driving circuit DRV1 in turn supplies at the output the signals driving the gates of the IGBTs 11, 12 13 and 14 corresponding to the instructions received from the control unit 130, whereby the four IGBTs 11, 12, 13 and 14 are driven so as to supply at the primary winding of the transformer T3 of the output unit 180 AC voltage and current configured to generate, through the output unit 180, the DC output current corresponding to the value selected by the user. The output unit 180 rectifies the voltage present at the secondary winding of the transformer T3, received by the power unit 140, and outputs the current selected by the user through the inductor LI and the output terminals 01 and 02. Advantageously, the control unit 130 controls and supervises the current delivered at the output through the current sensor SCI.
Differently, as previously stated, when the welding machine with adaptive power supply is connected to a single-phase supply voltage, the second transformer T1 of the detection unit 110 is powered and consequently the detection unit 110 generates a second detection signal at the positive output of the second rectifier circuit Bl, while the first transformer T2 of the same detection unit 110 is not powered.
Therefore, the control unit 130 detects the presence of a voltage across the neutral terminal E and the ground terminal GP, i.e. it receives a second power supply signal from the detection unit 110, and verifies the absence of voltage across the phase terminal F and the ground terminal GP, detecting that the welding machine with adaptive power supply is currently powered by single-phase voltage. At this point, the control unit 130 activates the control relay RL4, connecting the neutral cable N of the input interface 105 to the common intermediate node of the series connection of the capacitors Cl and C2, through the connection resistor R7, and then the control unit 130 supervises the precharge of the capacitors Cl and C2, that takes place through the auxiliary resistor R6 and the connection resistor R7, until the control unit 130 activates the precharge relay RL1 after a time ranging from 1 to 3 seconds, optionally equal to 2 seconds, consequently short-circuiting the auxiliary resistor R6 and the connection resistor R7. Thus, the single-phase voltage rectified through the three-phase rectifier device B3 will be present at the series of capacitors Cl and C2. At the same time, the control unit 130 sets the maximum value of current that can be delivered at the output terminals 01 and 02; this value is lower than the one set in the case where the welding machine is powered by a three-phase voltage. Subsequently, the control unit 130 reads the desired output current value set by the user through the user interface, and consequently it sets the driving circuit DRV1 through the driver terminals Pl and P2. The driving circuit DRV1 in turn supplies at the output the signals driving the gates of the IGBTs 11, 12 13 and 14 corresponding to the instructions received from the control unit 130, whereby the four IGBTs 11, 12, 13 and 14 are driven so as to supply at the primary winding of the transformer T3 of the output unit 180 an AC voltage and current configured to generate, through the output unit 180, the DC output current corresponding to the value selected by the user. The output unit 180 rectifies the voltage present on the secondary winding of the transformer T3, received by the power unit 140, and outputs the current selected by the user through the inductor LI and the output terminals 01 and 02. Advantageously, the control unit 130 controls and supervises the current delivered at the output through the current sensor SCI.
Advantageously, the internal circuitry 100 of the preferred embodiment of the welding machine with adaptive power supply also comprises a ventilation unit 160, configured to cause the internal temperature of the welding machine to decrease and comprising at least one ventilation element 165, an autotransformer T4, a first relay RL2 for powering the autotransformer T4 and a second relay RL5 for powering the autotransformer T4 (which are advantageously SPST relays). The at least one ventilation element 165 advantageously comprises at least one fan.
In particular, the ventilation unit 160 is controlled by the control unit 130 through the first relay RL2 for powering the autotransformer T4 and the second relay RL5 for powering the autotransformer T4, which are connected to the control unit 130 through two respective relay terminals RT2 and RT5.
More specifically, the second relay RL5 for powering the autotransformer T4, when activated, connects respective ends of the autotransformer T4 to the phase cable S and to the phase cable T.
It must be noted that such second relay RL5 for powering the autotransformer T4 can connect, when activated, respective ends of the autotransformerT4 to two cables selected from the three phase cables R, S and T.
Differently, the first relay RL2 for powering the autotransformer T4, when activated, connects respective ends of the autotransformerT4 to the phase cable S and to the neutral cable N.
It must be noted that such first relay RL2 for powering the autotransformer T4 can connect, when activated, respective ends of the autotransformer T4 to the neutral cable N and to a cable selected between the three phase cables R, S and T.
The autotransformer T4 has a first end node connected to a first cable selected from the three phase cables R, S, and T of the input interface 105, an intermediate node connected to the first relay RL2 for powering the autotransformer T4, and a second end node connected to the second relay RL5 for powering the autotransformer T4.
The autotransformer T4 is connected to the input of the at least one ventilation element 165 and is configured to supply it with an appropriate voltage to allow it to operate correctly.
When the control unit 130 detects, through the temperature sensor TH1, an internal temperature higher than a predetermined, optionally adjustable, threshold, it activates the ventilation unit 160. In particular, in the case where the control unit 130 has detected an input three-phase power supply, it activates the second relay RL5 for powering the autotransformer T4 (as shown in Figure 1), whereby the voltage present between the phase cables S and T is applied across the autotransformer T4 that consequently powers said at least one ventilation element 165. Differently, in the case where the control unit 130 has detected an input singlephase power supply, it activates the first relay RL2 for powering the autotransformer T4 (as shown in Figure 2), whereby the voltage present between the phase cable S and the neutral cable N is applied to the autotransformer T4 that consequently powers said at least one ventilation element 165.
Advantageously, the at least one display of the user interface is further configured to show to the user also the possible activation status of the ventilation unit 160.
The preferred embodiments of this invention have been described and a number of variations have been suggested hereinbefore, but it should be understood that those skilled in the art can make other variations and changes without so departing from the scope of protection thereof, as defined by the attached claims.

Claims

1. Welding machine with adaptive power supply, configured to automatically adapt to the input power supply alternatively selected between a three-phase power supply voltage and a single-phase power supply voltage, comprising an internal circuitry (100) comprising: an input interface (105), comprising at least one input connector configured to be connected to a mains power supply (200; 300), wherein the input interface (105) comprises three output phase cables (R, S, T), a neutral wire (N), and a circuit ground wire (G), and wherein: o when said mains power supply (200) has three-phase voltage, said three phase cables (R, S, T) of the input interface (105) are configured to be connected to respective phase cables (RM, SM, TM) of said mains power supply (200), and o when said mains power supply (300) has single-phase voltage, said three phase cables (R, S, T) of the input interface (105) are configured to be short-circuited and connected to the phase cable (PHI) of said mains power supply (300) and said neutral cable (N) of the input interface (105) is configured to be connected to the neutral cable (NM) of said mains power supply (300); a detection unit (110) connected to the three phase cables (R, S, T) and to the neutral cable (N) of the input interface (105) and configured to detect whether said mains power supply (200; 300) has three-phase voltage or single-phase voltage on the basis of a first voltage present between two cables selected from the three phase cables (R, S, T) of the input interface (105) and of a second voltage present between a cable selected from the three phase cables (R, S, T) of the input interface (105) and the neutral cable (N) of the input interface (105); a control unit (130) connected to the detection unit (110); a power unit (140) controlled by the control unit (130) connected to the input interface (105) and to an output unit (180), wherein the power unit (140) comprises a rectifier circuit (B3, Cl, C2) that includes a three-phase rectifier device (B3) connected to said three phase cables (R, S, T) of the input interface (105), the three-phase rectifier device (B3) having a first output terminal and a second output terminal which are respectively connected to a first end node and a second end node of a series connection of two electrical charge storage devices (Cl, C2) having a common intermediate node, and an output unit (180) configured to provide an output current and an output voltage at an output positive terminal (01) and an output negative terminal (02) of the welding machine with adaptive power supply; wherein the control unit (130) is configured to control the power unit (140) through a control relay (RL4) connected between the neutral cable (N) of the input interface (105) and said common intermediate node wherein: when the control unit (130) receives from the detection unit (110) a first detection signal indicating that said mains power supply (200) has three-phase voltage, said common intermediate node is floating, and when the control unit (130) receives from the detection unit (110) a second detection signal indicating that said mains power supply (300) has single-phase voltage, said common intermediate node is connected to the neutral cable (N) of the input interface (105) through at least one connection resistor.
2. Welding machine according to claim 1, wherein said detection unit (110) comprises: a first transformer (T2), the primary winding of which is connected to said two cables selected from the three phase cables (R, S, T) of the input interface (105); a second transformer (Tl), the primary winding of which is connected to said cable selected from the three phase cables (R, S, T) of the input interface (105) and to said neutral cable (N) of the input interface (105); a first rectifier circuit (B2) connected to the secondary winding of said first transformer (T2) and having a positive output and a negative output, wherein the positive output is connected to a phase terminal (F) of the control unit (130); a second rectifier circuit (Bl) connected to the secondary winding of said second transformer (Tl) and having a positive output and a negative output, wherein the positive output is connected to a neutral terminal (E) of the control unit (130); a stabiliser circuit (STI) configured to power said control unit (130), having o an input terminal (in), that is connected to the positive output of the first rectifier circuit (B2) and to the positive output of the second rectifier circuit (Bl), and o an output terminal (out), that is connected to a power supply terminal (V) of the control unit (130); wherein said detection unit (110) is configured to generate: said first detection signal on the positive output of the first rectifier circuit (B2); and said second detection signal on the positive output of the second rectifier circuit (Bl).
3. Welding machine according to claim 2, wherein the input terminal (in) of the stabiliser circuit (STI) is connected to the positive output of the first rectifier circuit (B2) through at least one respective diode (DI) and/or to the positive output of the second rectifier circuit (Bl) through at least one respective diode (D2).
4. Welding machine according to any one of the preceding claims, wherein said rectifier circuit (B3, Cl, C2) further includes a precharge relay (RL1) located: at the ends of said at least one connection resistor (R7), and at the ends of at least one auxiliary resistor (R6) connected between the first output terminal of the three-phase rectifier device (B3) and the first end node of said series connection of said two electrical charge storage devices (Cl, C2), wherein the control unit (130) is configured to control said precharge relay (RL1) to short-circuit said at least one connection resistor (R7) and said at least one auxiliary resistor (R6) after a precharge period subsequent to reception of said first detection signal or said second detection signal by the control unit (130).
5. Welding machine according to any one of the preceding claims, wherein said power unit (140) further comprises a power circuit (11, 12, 13, 14) that includes a plurality of semiconductor power switches, wherein said power circuit (11, 12, 13, 14) is driven by a driving circuit (DRV1) and powered by said rectifier circuit, wherein said driving circuit (DRV1) is controlled by the control unit (130).
6. Welding machine according to claim 5, wherein said plurality of semiconductor power switches of the power circuit (11, 12, 13, 14) includes one or more IGBTs or consists of a plurality of IGBTs.
7. Welding machine according to any one of the preceding claims, further comprising at least one current sensor (SCI) configured to detect a value of output current delivered by the output unit (180) and to transmit said detected current value to said control unit (130), wherein said control unit (130) dynamically controls the power unit (140) on the basis of said detected current value.
8. Welding machine according to any one of the preceding claims, further comprising at least one temperature sensor (TH1) configured to detect a temperature of said power unit (140) and to transmit said detected temperature to said control unit (130).
9. Welding machine according to claim 8, further comprising at least one ventilation unit (160) configured to be controlled by said control unit (130) and to cause the internal temperature of the welding machine to decrease, wherein when said detected temperature is 21 higher than a predetermined threshold, said control unit (130) activates the ventilation unit (160).
10. Welding machine according to claim 9, wherein said predetermined threshold is adjustable.
11. Welding machine according to claim 9 or 10, wherein the ventilation unit (160) comprises at least one ventilation element (165) configured to be powered by an autotransformer (T4), a first power supply relay (RL2) configured to power the autotransformer (T4) and a second power supply relay (RL5) configured to power the autotransformer (T4), wherein the autotransformer (T4) has a first end node connected to a first cable of said three phase cables (R, S, T ) of the input interface (105), an intermediate node connected to the first power supply relay (RL2), and a second end node connected to the second secondo power supply relay (RL5), wherein the first power supply relay (RL2) is further connected to said neutral cable (N) of the input interface (105), wherein the second power supply relay (RL5) is further connected to a second cable of said three phase cables (R, S, T) of the input interface (105) different from said first cable, wherein, when said detected temperature is higher than a predetermined threshold, said control unit (130): when said mains power supply (200) has three-phase voltage, activates the second power supply relay (RL5), and when said mains power supply (300) has single-phase voltage, activates the first power supply relay (RL2).
12. Welding machine according to any one of the preceding claims, further comprising a user interface that includes one or more selection devices configured to select a value of said output current supplied by said output unit (180), wherein said user interface is connected to the control unit (130) that is configured to control said power unit (140) on the basis of a selected value of said output current supplied by said output unit (180).
13. Welding machine according to claim 12, wherein said one or more selection devices are selected from the group comprising one or more setting potentiometers, one or more dipswitches, and a keyboard.
14. Welding machine according to any one of the preceding claims, further comprising at least one display, connected to said control unit (130), and configured to display one or more elements.
15. Welding machine according to claim 14, wherein said one or more elements are 22 selected from the group comprising or consisting of un currently delivered output current value, a voltage value currently present on the positive and negative output terminals (01, 02) of the welding machine, an internal and/or external temperature value, a type of power supply detected at the input between single-phase voltage power supply and three-phase voltage power supply.
PCT/IB2022/057238 2021-08-06 2022-08-04 Welding machine with adaptive power supply WO2023012712A1 (en)

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Publication number Priority date Publication date Assignee Title
JP2016140885A (en) * 2015-02-02 2016-08-08 株式会社ダイヘン Power supply device, and welding power supply device

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CN201035350Y (en) 2007-05-17 2008-03-12 宋庆发 General purpose type arc welder electricity economizer

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Publication number Priority date Publication date Assignee Title
JP2016140885A (en) * 2015-02-02 2016-08-08 株式会社ダイヘン Power supply device, and welding power supply device

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