JP2010125458A - Output control method of welding power source - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve balance of output current in each inverter circuit when a plurality of inverter circuits built in a power source unit are arranged in parallel, and parallel operation is performed. <P>SOLUTION: In the output control method of a welding power source, N pieces of output control circuits are connected in parallel, and an output voltage set value Er for setting the output voltage of the welding power source, and an inductance set value Lr for setting a proper inductance value of the welding power source, are preliminarily set. A welding voltage during welding is detected and, simultaneously, a first output current of a first output control circuit or an N'th output current of an N'th output control circuit is detected. A current setting variance ΔIr=(Er-Vd)/Lr is calculated with a welding voltage detection value Vd as input, and a welding current control set value is calculated by integrating the current setting variance ΔIr, and a welding current command value is calculated by making the welding current control set value 1/N times. Then, the output is controlled in the manner that the first output current value of the first output control circuit or the N'th output current value of the N'th output control circuit is nearly equalized to the welding current command value. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a welding power source output control method in which a plurality of welding power source output control circuits are provided in parallel.

  In CO2, MAG welding, etc., a DC reactor having a different internal inductance value is provided depending on the type of welding power source or the rated output current, the difference in internal inductance value caused by this DC reactor, and the welding power source output terminal and welding torch or In order to stabilize welding, the inductance value is adjusted in accordance with the difference in the external inductance value, which varies depending on the length and the length of the welding cable connecting the base material. If the adjustment of the inductance value is neglected, the welding state becomes unstable due to the deviation from the appropriate inductance value.

  FIG. 4 shown below is a block diagram of a welding power source having an electronic reactor function that always maintains an appropriate inductance value even when the internal inductance value and the external inductance value change. Hereinafter, a description will be given with reference to FIG.

  In FIG. 4, an output control circuit INV includes a primary rectifier circuit that rectifies a commercial AC power supply (not shown) and outputs a DC voltage, a smoothing capacitor that is provided in parallel with the primary rectifier circuit and smoothes the DC voltage, and a DC voltage. A first inverter circuit for converting the output of the first inverter circuit into a high-frequency AC voltage, a first main transformer for converting the output of the first inverter circuit into a high-frequency AC voltage suitable for a predetermined load, and the output of the first main transformer The output control circuit INV is configured by a secondary rectifier circuit that rectifies power, performs output control with a commercial power supply as an input, and outputs an output current.

  In FIG. 4, the output current detection circuit ID detects the output current of the output control circuit INV and outputs it as an output current detection signal Id, and the welding voltage detection circuit VD detects the welding voltage v and detects the welding voltage detection signal Vd. Output as. The direct current reactor DCL smoothes the output of the output control circuit INV and supplies it to the welding torch 4.

  The output voltage setting circuit ER shown in FIG. 4 sets a predetermined output voltage setting signal Er. The inductance setting circuit LR outputs an inductance setting signal Lr corresponding to the appropriate inductance value Lm. The current setting change amount calculation circuit DIR, the welding voltage detection signal Vd, the output voltage setting signal Er, and the inductance setting signal Lr shown in the figure are input, and the calculation of (Er−Vd) / Lr is performed to obtain the current setting change amount signal. ΔIr is obtained. The integration circuit IIR calculates the welding current control setting signal Irc by integrating the current setting change amount signal ΔIr.

  The current error amplification circuit API amplifies an error between the value of the welding current control setting signal Irc and the output current detection signal Id and outputs a current error amplification signal APi. The output control circuit INV controls the output current in accordance with the current error amplification signal APi. Therefore, the output current detection signal Id becomes substantially equal to the welding current control setting signal Irc.

FIG. 5 is an equivalent circuit of the welding power source apparatus shown in FIG. 4 having a constant voltage characteristic that maintains an appropriate inductance even when the internal inductance value and the external inductance value change.
The principle of maintaining an appropriate inductance even when the internal inductance value and the external inductance value change using this equivalent circuit will be described.

FIG. 5A is an equivalent circuit diagram of a welding power source having a constant voltage characteristic having an appropriate inductance value Lm. In the figure, the following formula is established.
E = Lm · di / dt + v
However, E [V] is an output voltage, Lm [H] is an appropriate inductance value, i [A] is a welding current, and v [V] is a welding voltage.
When the above equation is arranged, the following equation is obtained.
di / dt = (E−v) / Lm
Integrating both sides gives the following formula.
i = ∫ ((E−v) / Lm) · dt
Here, when the welding current i is replaced with the welding current control set value Irc, the output voltage E is replaced with the output voltage set value Er, and the appropriate inductance value Lm is replaced with the inductance set value Lr, the following equations are obtained.
Irc = ∫ ((Er−v) / Lr) · dt
An equivalent circuit corresponding to the above equation is shown in FIG. In the figure, the welding voltage v is detected and the welding current control set value Irc corresponding to the welding current i of the constant current source CC is controlled to be the calculated value of the above equation. Thereby, the change of the welding current i with respect to the fluctuation of the welding load becomes the same as that in FIG.

FIG. 5C shows an equivalent circuit when the values of the internal inductance and the external inductance are Lio. In this figure, even if Lr of Irc = ∫ ((Er−v) / Lr) · dt remains Lm, the change of the welding current i with respect to the fluctuation of the welding load is the same. That is, even if the values Lio of the internal inductance and the external inductance change, the above control method is not affected. Therefore, even if the internal inductance value changes due to variations in the parts constituting the welding power source device, and the external inductance value changes due to the length and routing of the welding cable, the inductance setting value Lr is always set to an appropriate inductance value. Become.
(For example, Patent Document 1)

JP 2003-305571 A

A conventional welding power source has an electronic reactor function that always maintains an appropriate inductance value even when the internal inductance value and the external inductance value change.
There is a demand for a welding power source in which a plurality of output control circuits having this function are provided in the welding power source in parallel to increase the output current.
However, the output control circuit of this power supply device has a constant voltage characteristic, and when the output control circuit having this constant voltage characteristic is provided in parallel with, for example, N units, the components such as the semiconductor elements constituting the output control circuit vary. As a result, a slight deviation occurs in the output voltage, and when this state continues, one output current of the output control circuit increases, the other output current decreases and the current balance is lost. Current flows too much in the semiconductor element, leading to deterioration of parts due to heat loss.

  Therefore, the present invention provides a welding power source that is not affected by changes in the internal inductance value and the external inductance value even when the output control circuit is provided in parallel, for example, N units, and that the output current is substantially the same. Objective.

  In order to solve the above-described problem, the present invention provides an output voltage in which N output control circuits are connected in parallel, a DC reactor is connected between the connection point and the output terminal, and an output voltage of the welding power source is set. A set value Er and an inductance set value Lr for setting an appropriate inductance value for the welding power source are set in advance, a welding voltage during welding is detected, and the first output current or the Nth output current of the first output control circuit is detected. The Nth output current of the output control circuit is detected, the current setting change amount ΔIr = (Er−Vd) / Lr is calculated using the welding voltage detection value Vd as an input, and the current setting change amount ΔIr is integrated to perform welding. A current control set value is calculated, a welding current command value is calculated by multiplying the welding current control set value by 1 / N, and the first output current value of the first output control circuit is equal to the welding current command value. To be approximately equal The welding power supply output control method is characterized in that control is performed and control is performed so that an Nth output current value of the Nth output control circuit is substantially equal to the welding current command value.

  According to a second aspect of the invention, the welding current control set value is distributed based on a ratio of rated output current values of the first output control circuit to the Nth output control circuit, and the first welding current command value to the first welding current command value. N welding current command values are generated, and the first output current value of the first output control circuit is controlled to be substantially equal to the first welding current command value, or the Nth output control circuit. The welding power output control method according to claim 1, wherein the Nth output current value is controlled to be substantially equal to the Nth welding current command value.

  According to the first aspect of the invention, the welding current command value is calculated by multiplying the welding current control set value by 1 / N according to the number of output control circuits (for example, N units) connected in parallel, and the calculated welding is performed. When the N output control circuits are controlled based on the current command value, the output currents are substantially the same, the current balance is achieved, the output current can be increased, and the internal inductance is maintained even when the output control circuits are provided in parallel. Since it is not affected by the change of the value and the external inductance value, the arc is stabilized and the welding quality is improved.

  According to the second invention, N output control circuits having different rated output current values are provided in parallel, and the welding current control set value is distributed based on the ratio of the rated output current values. When each output control circuit is controlled based on the welding current command value, parallel operation is possible even with output control circuits having different rated output current values.

  FIG. 1 is an electrical connection diagram for carrying out an output control method for a welding power source according to Embodiment 1 of the present invention. In the figure, the same reference numerals as those in FIG. 4 have the same configuration, and therefore description thereof will be omitted. Only components having different reference numerals will be described.

  The first output control circuit INV1 and the second output control circuit INV2 connected in parallel as shown in FIG. 1 have the same configuration as the output control circuit INV shown in FIG. 4, and the first output control circuit INV1 is a commercial power supply. When the first output current is output by performing the output control, the second output control circuit INV1 outputs the second output current by performing the output control with the commercial power supply as an input.

  The first distribution circuit DI1 halves the welding current control setting signal Irc and outputs it as a welding current command signal Ira.

  The first current error amplification circuit API1 amplifies the error between the welding current command signal Ira and the first output current detection signal Id1, and outputs a first current error amplification signal APi1. The first output control circuit INV1 constitutes a first constant current source CC1 that performs constant current control of the output current in accordance with the first current error amplification signal APi1.

  The second current error amplification circuit API2 amplifies an error between the welding current command signal Ira and the second output current detection signal Id2, and outputs a second current error amplification signal APi2. The second output control circuit INV2 constitutes a second constant current source CC2 that performs constant current control of the output current in accordance with the second current error amplification signal APi2.

Next, FIG. 2 is the equivalent circuit of the present invention shown in FIG. 1, and the operation will be described using this equivalent circuit.
FIG. 2A is an equivalent circuit diagram of a welding power source having a constant voltage characteristic having an appropriate inductance value Lm. In the figure, the following formula is established.
di / dt = (E−v) / Lm
Integrating both sides gives the following formula.
i = ∫ ((E−v) / Lm) · dt
Here, when the welding current i is replaced with the welding current control set value Irc, the output voltage E is replaced with the output voltage set value Er, and the appropriate inductance value Lm is replaced with the inductance set value Lr, the following equations are obtained.
Irc = ∫ ((Er−v) / Lr) · dt
An equivalent circuit corresponding to the above equation is shown in FIG. In the figure, the welding voltage v is detected and controlled based on the welding current control set value 1/2 · Irc (corresponding to the welding current i / 2 of the first constant current source CC1, and the second constant current source CC2 is controlled. Is also controlled based on the welding current control set value 1/2 · Irc, so that the change of the welding current i with respect to the fluctuation of the welding load is the same as in FIG.

  That is, two constant current sources CC are connected in parallel from the equivalent circuit shown in FIG. 2B, and the welding current control set value Irc is halved by the first distribution circuit DI1 shown in FIG. The command signal Ira (1/2 · Irc) is calculated. When the output currents of the first constant current source CC1 and the second constant current source CC2 are controlled based on the welding current command signal Ira (1/2 · Irc), the values of the two output currents are substantially the same. Become.

  FIG. 2C shows an equivalent circuit when the internal inductance value and the external inductance value are Lio. In the same figure, even if Lr = Lm, the change of each welding current i / 2 with respect to the fluctuation of the welding load is the same. That is, even if the internal inductance value and the external inductance value Lio change, the inductance setting value Lr is always an appropriate inductance value.

As described above, in the present invention, a welding power source is formed in which the two output currents are substantially balanced and are not affected by changes in the internal inductance value and the external inductance value.
Furthermore, in the present invention, N output control circuits are connected in parallel, and a DC reactor is connected between the connection point and the output terminal. However, the N output control circuits disposed in the welding power source are connected to each other. Since the inductance value is generated by the length and the routing of the welding cable to be connected, it is not necessary to provide a DC reactor.

[Embodiment 2]
FIG. 3 is an electrical connection diagram for carrying out the output control method of the welding power source according to the second embodiment of the present invention. In this figure, the same reference numerals as those in FIG. 1 and FIG. 4 have the same configuration, and therefore description thereof will be omitted. Only components having different reference numerals will be described.

  In the first output control circuit INV1 and the second output control circuit INV2 shown in FIG. 3, the ratio of the rated output current values is, for example, 2: 1 and two output control circuits having different rated output current values are used. It is provided in parallel.

  The second distribution circuit DI2 shown in FIG. 3 increases the welding current control setting signal Irc by 2/3 (2/3 · Irc) and outputs it as the second welding current command signal Ira2, and the third distribution circuit. DI3 multiplies the welding current control setting signal Irc by 1/3 (1/3 · Irc) and outputs it as a third welding current command signal Ira3.

  The first current error amplification circuit API1 shown in FIG. 3 amplifies the error between the second welding current command signal Ira2 and the first output current detection signal Id1, and outputs a first current error amplification signal APi1. . Then, the first output control circuit INV1 controls the output current according to the first current error amplification signal APi1.

  The second current error amplification circuit API2 shown in FIG. 3 amplifies the error between the third welding current command signal Ira3 and the second output current detection signal Id2, and outputs a second current error amplification signal APi2. . Then, the second output control circuit INV2 controls the output current according to the second current error amplification signal APi2.

  From the above, even when the rated current value of the first output control circuit INV1 connected in parallel is 200A, for example, and the rated current value of the second output control circuit INV2 is not the same as 100A, the output control circuit is provided in parallel. Parallel operation is possible.

It is an electrical connection diagram of a welding power source for carrying out the output control method according to Embodiment 1 of the present invention. It is an equivalent circuit diagram for demonstrating Embodiment 1 of this invention. It is an electrical connection diagram of the welding power source for implementing the output control method concerning Embodiment 2 of the present invention. It is an electrical connection diagram of a welding power source for implementing the output control method of a prior art. It is an equivalent circuit diagram for demonstrating a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Welding wire 2 Base material 3 Arc 4 Welding torch 5 Feed roll API Current error amplifier circuit APIi Current error amplifier signal API1 First current error amplifier circuit APi1 First current error amplifier signal API2 Second current error amplifier circuit API2 Second current error amplification signal CC constant current source CC1 first constant current source CC2 second constant current source DI1 first distribution circuit DI2 second distribution circuit DI3 third distribution circuit DCL DC reactor DIR Current setting change Quantity calculation circuit E1 First output voltage E2 Second output voltage ER Output voltage setting circuit Er Output voltage setting signal (output voltage setting value)
ID output current detection circuit id output current detection signal ID1 first output current detection circuit id1 first output current detection signal ID2 second output current detection circuit id2 second output current detection signal IIR integration circuit INV output control circuit INV1 First output control circuit INV2 Second output control circuit Irc Welding current control setting signal Ira Welding current command signal Ira2 Second welding current command signal Ira3 Third welding current command signal Lio Internal and external inductance value Lm Proper inductance value LR Inductance setting circuit Lr Inductance setting signal v Welding voltage VD Welding voltage detection circuit Vd Welding voltage detection signal ΔIr Current setting change amount (signal)

Claims (2)

  N output control circuits are connected in parallel, a DC reactor is connected between the connection point and the output terminal, and an output voltage set value Er for setting the output voltage of the welding power source and an appropriate inductance value for the welding power source are set. An inductance setting value Lr to be set in advance, a welding voltage during welding is detected, and a first output current of the first output control circuit or an Nth output current of the Nth output control circuit is detected; The welding voltage detection value Vd is input to calculate a current setting change amount ΔIr = (Er−Vd) / Lr, and the current setting change amount ΔIr is integrated to calculate a welding current control setting value, and the welding current control setting is calculated. The welding current command value is calculated by multiplying the value by 1 / N, and the first output current value of the first output control circuit is controlled to be substantially equal to the welding current command value, or the Nth Output control circuit An output control method for a welding power source, wherein an output current value of N is controlled to be substantially equal to the welding current command value.   The welding current control set value is distributed based on a ratio of rated output current values of the first output control circuit to the Nth output control circuit, and the first welding current command value to the Nth welding current command value. And the first output current value of the first output control circuit is controlled to be substantially equal to the first welding current command value, or the Nth output current of the Nth output control circuit. 2. The output control method for a welding power source according to claim 1, wherein a value is controlled to be substantially equal to the Nth welding current command value.

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