JP2005081379A - Arc welder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that, in an arc welder provided with a plurality of main transformers arranged in parallel, when a difference arises in electric current flowing in the main transformers, the current flows biasedly to one side and a transformer bearing a larger load is burnt due to overloading. <P>SOLUTION: In an arc welder, 1st and 2nd main transformers are arranged in parallel and connected to a commercial AC power source, 1st and 2nd power main circuits are connected to the secondary sides of the 1st and 2nd main transformers to rectify a secondary voltage and to conduct power control, a power control circuit controls an output of the 1st and 2nd power main circuits according to a set value of output current, and a DC reactor smoothes the output. In the arc welder, there are provided an electric current difference detecting circuit, which calculates a difference value of input current of the 1st and 2nd main transformers, and a warning circuit, which determining that a uniform state of the input current of the 1st and 2nd main transformers is collapsed when the calculated value is a reference value or more, stops the operation of the power control circuit, and which determining that the uniform state is kept when the calculated value is smaller than the reference value, actuates the operation of the power control circuit. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention connects a plurality of main transformers in parallel, calculates the difference between the input currents of the main transformers connected in parallel, and stops the output when the calculated difference value exceeds a predetermined reference value. The present invention relates to an arc welding machine.

  Conventionally, as shown in FIG. 8, the first main circuit switch MS1 and the second main circuit switch MS2 that are connected to a commercial AC power source to open and close the input and the first main circuit switch MS1 are connected. A first main transformer INT1 that converts a commercial AC power source into a voltage suitable for arc welding, and a second main transformer INT2 that is connected to the second main circuit switch MS2 and converts the commercial AC power source into a voltage suitable for arc welding. A main transformer INT2, a first power main circuit SCR1 connected to the secondary side of the first main transformer INT1 and rectifying and controlling the primary side voltage; and 2 of the second main transformer INT2 The second power main circuit SCR2, which is connected to the secondary side and rectifies and power-controls the secondary side voltage, the power-on switch SW1 that controls the command signal to turn on the commercial AC power, and the power-on switch SW1 are turned on. The above commercial AC power supply As soon as it is input, the first switch drive signal Mf1 is output to close the first main circuit switch MS1, and then the second switch drive signal Mf2 is output after a predetermined switch delay time elapses. A switch control circuit MKT that outputs and closes the second main circuit switch MS2, and outputs of the first power main circuit SCR1 and the second power main circuit SCR2 when an activation signal Ts is input from the outside. A power control circuit SCT to be controlled and a DC reactor DCL connected to the output side of the first power main circuit SCR1 and the second power main circuit SCR2 to smooth the output are provided.

  The switch control circuit MKT outputs the first switch drive signal Mf1 and the second switch drive signal Mf2 in this order, and after the second switch drive signal Mf2 is output, the switch control circuit MKT determines in advance. When the time T2 has elapsed, the power control circuit start signal Msc is output, and the power control circuit SCT receives the first power main circuit when both the power control circuit start signal Msc and the start signal Ts are input. The outputs of SCR1 and the second power main circuit SCR2 are controlled. As described above, since the magnetizing inrush current flows in a time-sharing manner when the commercial AC power is turned on, the value of the magnetizing inrush current can be reduced. However, if the combined output current tends to flow biased to one of the main transformers in spite of parallel operation, it becomes overloaded and burns out.

Japanese Patent Application No. 2002-341696

  In an arc welding machine with a plurality of main transformers and power main circuits in parallel, a difference occurs in the currents flowing through the main transformers due to defects in the thyristor elements etc. of the power main circuit, even though they are operating in parallel. However, if the combined output current has a strong tendency to flow biased to one of the main transformers, the larger load becomes overloaded and burns out.

  In order to solve the above-mentioned problems, the first invention is connected to a commercial AC power source and converted to a voltage suitable for arc welding, and connected to the commercial AC power source and the first main transformer INT1. The main transformer INT1 is connected in parallel to the second main transformer INT2 for converting the commercial AC power source into a voltage suitable for arc welding, and is connected to the secondary side of the first main transformer INT1. A first power main circuit SCR1 composed of a switching element for rectifying and controlling the power of the secondary side voltage, and a switching element connected to the secondary side of the second main transformer INT2 for rectifying and controlling the power of the secondary side voltage When the activation signal Ts is turned on from the outside, the operation starts and the first power main circuit SCR1 and the second power according to the predetermined output current set value Rv are started. Main circuit SCR2 In the arc welding machine for connecting the output of the power control circuit SC for controlling the output, the output of the first power main circuit SCR1 and the output of the second power main circuit SCR2, and smoothing by the DC reactor DCL, the first A current difference which calculates a difference value (i1-i2) between the primary side input current i1 of the main transformer INT1 and the primary side input current i2 of the second main transformer INT2 and outputs it as a current difference detection signal Wc When the value of the detection circuit and the current difference detection signal Wc is greater than or equal to a predetermined reference value Ir, the uniform state of the primary input currents of the first main transformer INT1 and the second main transformer INT2 is It is determined that it has collapsed, the input current alarm signal Cp is output, the operation of the power control circuit SC is stopped, and the primary side input current is in a uniform state when the value of the current difference detection signal Wc is less than the reference value Ir. There a determination to stop the output of the input current alarm signal Cp is an arc welder, characterized in that an input current alarm circuit CP to continue the operation of the power control circuit SC.

  In the second invention, the current difference detection circuit causes the primary current U phase of the first main transformer INT1 to be loosely inserted into the input current detector Ct, and the second main transformer INT2 The arc welding according to claim 1, wherein a difference value (i1-i2) of the primary side input current i is calculated by loosely inserting a primary side wiring U phase in a direction opposite to the loosely inserted wiring. Machine.

  In the arc welding machines of the first and second inventions, when a plurality of main transformers are connected in parallel, the difference values of the respective input currents are sequentially monitored, and current flows biased to one of the main transformers. In order to stop the operation after determining that it is abnormal, it is possible to prevent the main transformer or the like from being overloaded and burned out.

[Embodiment 1]
FIG. 1 is an electrical connection diagram of the arc welder of the present invention, in which a first power main circuit SCR1 and a second power main circuit SCR2 are output control elements (switching elements composed of thyristor elements, chopper transistors, and the like). As an arc welding machine for supplying DC power to an arc load generated between the welding torch TH and the workpiece CW. In FIG. 1, a first main transformer INT1 and a second main transformer INT2 (for example, rated at 1000 A) are arranged in parallel, and the first main transformer INT1 and the second main transformer INT2 are arranged. The first power main circuit SCR1 and the second power main circuit SCR2 are connected to the secondary side of the first power main circuit SCR2, and a DC reactor DCL is connected to the outputs of the first power main circuit SCR1 and the second power main circuit SCR2. Main circuit portion is formed.

  The first main transformer INT1 and the second main transformer INT2 shown in FIG. 1 convert the commercial AC power source into a voltage suitable for arc welding. The first power main circuit SCR1 rectifies and power-controls the secondary side voltage of the first main transformer INT1, and the second power main circuit SCR2 controls the secondary voltage of the second main transformer INT2. Side voltage is rectified and power controlled.

  The output current setting circuit RV sets and outputs a predetermined output current set value Rv, and the start switch TS controls the start signal Ts on and off. The main control circuit MC is formed by the input current alarm circuit CP, the reference value setting circuit IR, and the power control circuit SC shown in FIG.

  The current difference detection circuit is formed by an input current detector CT and a full-wave rectifier circuit WC, and the input current detector CT is one phase (for example, U phase) on the input side of the first main transformer INT1. The difference between the input current i1 and the input current i2 of one phase (for example, U phase) on the input side of the second main transformer INT2 is calculated and output as the input current detection signal Ct. The full-wave rectifier circuit WC performs full-wave rectification on the input current detection signal Ct and outputs it as a current difference detection signal Wc.

  The input current alarm circuit CP shown in FIG. 2 starts to operate when the activation signal Ts is turned on, compares the value of the current difference detection signal Wc with the reference value Ir predetermined by the reference value setting circuit IR, and compares the current difference. If the value of the detection signal Wc is less than the reference value Ir, the input current i1 of the first main transformer INT1 and the input current i2 of the second main transformer INT2 are in a uniform state (i1 = i2). The input current alarm signal Cp is set to the Low level, and when the value of the current difference detection signal Wc is equal to or greater than the reference value Ir, it is determined that the uniform state has collapsed, and the input current alarm signal Cp is set to the High level and output.

  The power control circuit SC starts operating when the activation signal Ts is turned on, and performs output control of the first power control signal Sc1 and the second power control signal Sc2 according to the value of the output current set value Rv. Further, when the input current alarm signal Cp becomes High level, the output of the first power control signal Sc1 and the second power control signal Sc2 is stopped.

  The first power main drive circuit SD1 shown in FIG. 1 converts the level of the first power control signal Sc1, outputs it as the first power main drive signal Sd1, and controls the power of the first power main circuit SCR1. The second power main drive circuit SD2 converts the level of the second power control signal Sc2, outputs it as the second power main drive signal Sd2, and controls the power of the second power main circuit SCR2.

  FIG. 3 is a detailed view of the input current detector CT shown in FIG. The input current detector CT detects the input current i1 by loosely inserting the primary side wiring (for example, U phase) of the first main transformer INT1, and detects the primary side wiring ( For example, when the input current i2 that is reversed by loose insertion of the U phase in the opposite direction is detected and the difference value of the detected input current is in a uniform state, the relationship of i1 = i2 is established. Therefore, the difference value of the input current detector CT is i1-i2 = 0, and the value of the input current detection signal Ct is output as 0.

  The operation of the present invention shown in FIG. 1 will be described with reference to the waveform timing chart of FIG. 4A shows the U-phase input current waveform i1 of the first main transformer INT1, and FIG. 4B shows the inverted waveform of the U-phase input current waveform i2 of the second main transformer INT2. Show. 4 (C) shows the input current detection signal Ct, FIG. 4 (D) shows the current difference detection signal Wc obtained by full-wave rectification of the input current detection signal Ct, and FIG. 4 (E) shows the start signal Ts. 4 (F) shows the input current alarm signal Cp, FIG. 4 (G) shows the first power control signal Sc1, and FIG. 4 (H) shows the second power control signal Sc2.

  When the activation signal Ts is turned on at time t = t1 shown in FIG. 4, the input current waveform i1 shown in FIG. 4A and the inverted input current waveform i2 shown in FIG. The input current detector CT detects the difference value (i1-i2) between the input current waveform i1 and the input current waveform i2, and outputs it as an input current detection signal Ct shown in FIG. The full-wave rectifier circuit WC performs full-wave rectification on the input current detection signal Ct and outputs it as a current difference detection signal Wc.

  The input current alarm circuit CP compares the value of the current difference detection signal Wc with the reference value Ir set by the reference value setting circuit IR, and because the value of the current difference detection signal Wc is less than the reference value Ir, It is determined that the input current i1 of the first main transformer INT1 and the input current i2 of the second main transformer INT2 are in a uniform state, and the input current alarm signal Cp is set to the low level.

  The power control circuit SC operates when the input current alarm signal Cp is at the low level and the activation signal is on, and according to the output current set value Rv, the first power control signal Sc1 shown in FIG. Output control of the second power control signal Sc2 shown in FIG. Further, the first power main drive circuit SD1 performs level conversion when the first power control signal Sc1 is input, and outputs the first power main drive signal Sd1 to control the power of the first power main circuit SCR1, When the second power control signal Sc2 is input, the second power main drive circuit SD2 performs level conversion and outputs the second power main drive signal Sd2 to control the power of the second power main circuit SCR2.

  At time t = t2, when the uniformity of the input current i1 shown in FIG. 4A and the inverted input current i2 shown in FIG. 4B is lost, the current difference detection signal Wc shown in FIG. To increase. As a result, when the value of the current difference detection signal Wc exceeds the reference value Ir at time t = t3, the input current alarm circuit CP determines that the input current of the first main transformer INT1 and the second main transformer INT2 It is determined that the uniform state with the input current of the input current has collapsed, and the input current alarm signal Cp is set to High level and output.

  When the input current alarm signal Cp becomes High level, the power control circuit SC stops outputting the first power control signal Sc1 shown in FIG. 4 (G) and the second power control signal Sc2 shown in FIG. 4 (H). To do. Further, the abnormality display lamp LED is turned on when the input current alarm signal Cp becomes High level. Subsequently, when the activation signal Ts is turned off, the input current alarm circuit CP sets the input current alarm signal Cp to Low level and turns off the abnormality display lamp LED.

  When the activation signal Ts shown in FIG. 4D is turned off at time t = t4, the input current alarm circuit CP and the power control circuit SC stop operating, and each output signal is set to a low level.

  In the above description, the U-phase input current of the commercial AC power supply is used, but the V-phase and the W-phase may be used. Also, the input current alarm circuit CP shown in FIG. 2 operates regardless of whether the activation signal Ts is on or off. When the value of the current difference detection signal Wc is equal to or higher than the reference value Ir, the input current alarm signal Cp is set to High. It may be output as a level.

[Embodiment 2]
FIG. 5 is an electrical connection diagram of the arc welder according to the second embodiment. In the figure, the same reference numerals as those in the electrical connection diagram of the arc welder of the present invention shown in FIG.

  The first power main circuit SCR1, the second power main circuit SCR2, and the third power main circuit SCR3 shown in FIG. 5 are connected to the welding torch TH as an output control element (a switching element including a thyristor element and a chopper transistor). DC power is supplied to the arc load generated between the workpiece CW. In FIG. 5, a plurality of first main transformers INT1, second main transformers INT2, and third main transformers INT3 (for example, rated at 1000A) are arranged in parallel, and the first main transformers INT1, A first power main circuit SCR1, a second power main circuit SCR2, and a third power main circuit SCR3 are connected to the secondary side of the second main transformer INT2 and the third main transformer INT3, A DC reactor DCL is connected to the outputs of one power main circuit SCR1, second power main circuit SCR2, and third power main circuit SCR3 to form a main circuit section.

  The second main control circuit unit MC2 shown in FIG. 6 is formed by an input current alarm circuit CP, a reference value setting circuit IR, and a second power control circuit SC2.

  The second input current detector CT2 shown in FIG. 7 includes 2i2 obtained by doubling the input current i1 of the first main transformer INT1, the input current i2 of the second main transformer INT2, and the third main transformer. The difference value (2i1-i2-i3) from the input current i3 of the device INT3 is calculated and output as the second input current detection signal Ct2. The second current difference detection circuit is formed by the second input current detector CT2 and the full wave rectification circuit WC, and the full wave rectification circuit WC performs the full wave rectification on the second input current detection signal Ct2. And output as a current difference detection signal Wc.

  The input current alarm circuit CP shown in FIG. 6 starts to operate when the activation signal Ts is input, compares the value of the current difference detection signal Wc with the reference value Ir predetermined by the reference value setting circuit IR, and compares the current difference. If the value of the detection signal Wc is less than the reference value Ir, the input current i1 of the first main transformer INT1, the input current i2 of the second main transformer INT2, and the input current i3 of the third main transformer INT3. Is determined to be in a uniform state, the input current alarm signal Cp is set to a low level, and when the value of the current difference detection signal Wc is equal to or greater than the reference value Ir, it is determined that the uniform state has collapsed and the input current alarm signal Cp is determined. Output at High level.

  The second power control circuit SC2 starts to operate when the activation signal Ts is input, and the first power control signal Sc1, the second power control signal Sc2, and the third power control signal according to the output current set value Rv. Output control of Sc3 is performed. Further, when the input current alarm signal Cp becomes High level, the output of the first power control signal Sc1, the second power control signal Sc2, and the third power control signal Sc3 is stopped.

  The first power main drive circuit SD1 shown in FIG. 5 performs level conversion on the first power control signal Sc1, outputs it as the first power main drive signal Sd1, and controls the power of the first power main circuit SCR1. The second power main drive circuit SD2 converts the level of the second power control signal Sc2, outputs it as the second power main drive signal Sd2, controls the power of the second power main circuit SCR2, and performs the third power main drive. The circuit SD3 converts the level of the third power control signal Sc3 and outputs it as a third power main drive signal Sd3 to control the power of the third power main circuit SCR3. It is also possible to arrange four or more main transformers in parallel.

It is an electrical connection diagram of the arc welder of the present invention. It is a detailed circuit diagram of the main control circuit shown in FIG. It is a detailed block diagram of the input current detector shown in FIG. It is a waveform timing diagram for demonstrating operation | movement of the arc welder of this invention. It is an electrical connection figure of the arc welder of 2nd Embodiment. FIG. 6 is a detailed circuit diagram of a second main control circuit shown in FIG. 5. It is a detailed block diagram of the 2nd input current detector shown in FIG. It is an electrical connection figure of the arc welding machine of a prior art.

Explanation of symbols

CT input current detector CT2 second input current detector CW workpiece CP input current alarm circuit DCL DC reactor IR reference value setting circuit INT1 first main transformer INT2 second main transformer INT3 third main transformer LED Abnormal display lamp MC Main control circuit part MC2 Second main control circuit part RV Output current setting circuit SC Power control circuit SC2 Second power control circuit SD1 First power main drive circuit SD2 Second power main drive circuit SD3 Third power main drive circuit SCR1 First power main circuit SCR2 Second power main circuit SCR3 Third power main circuit TS Start switch TH Welding torch WC Full-wave rectifier circuit Ct Input current detection signal Ct2 Second input Current detection signal Cp Input current alarm signal Rv Output current set value Sc1 First power control signal Sc2 Second power control Issue Sc3 third power control signals Sd1 first power main driving signal Sd2 second power main drive signal Sd3 third power main drive signal Ts activation signal
Wc Current difference detection signal

Claims (2)

  A first main transformer that is connected to a commercial AC power source and converts the voltage into a voltage suitable for arc welding, and connected to the commercial AC power source and arranged in parallel with the first main transformer, A first main power comprising a second main transformer for converting to a voltage suitable for arc welding, and a switching element connected to the secondary side of the first main transformer to rectify and control the secondary side voltage. A circuit, a second power main circuit comprising a switching element connected to the secondary side of the second main transformer and rectifying and controlling the secondary side voltage, and starts when an activation signal is input from the outside. A power control circuit for controlling outputs of the first power main circuit and the second power main circuit in accordance with a predetermined output current set value; an output of the first power main circuit; Connect to the output of the main power circuit and smooth by the DC reactor In an arc welder, a current difference detection that calculates a difference value between a primary side input current of the first main transformer and a primary side input current of the second main transformer and outputs it as a current difference detection signal. When the circuit and the value of the current difference detection signal are equal to or greater than a predetermined reference value, it is determined that the uniform state of the primary side input current of the first main transformer and the second main transformer has collapsed. An input current alarm signal is output to stop the operation of the power control circuit, and when the value of the current difference detection signal is less than the reference value, it is determined that the primary side input current is in a uniform state and an input current alarm is issued. An arc welding machine comprising: an input current alarm circuit that stops signal output and continues operation of the power control circuit. The current difference detection circuit is configured to cause the input current detection unit to loosely insert the primary side wiring of the first main transformer and reverse the primary side wiring of the second main transformer to the loose insertion. The arc welding machine according to claim 1, wherein the difference value of the primary side input current is calculated by loose insertion in a direction.

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