阅读说明：本技术 电弧加工用电源装置以及电弧加工用电源装置的控制方法 (Power supply device for arc machining and method for controlling power supply device for arc machining ) 是由 滨野善行 田畑芳行 森川彻也 三泽司 堀江宏太 于 2018-03-08 设计创作，主要内容包括：本公开提供一种电弧加工用电源装置以及电弧加工用电源装置的控制方法。根据构成逆变器电路(INV1、INV2)的开关元件的温度的测定值和输出电流所涉及的设定值,选择多个逆变器电路(INV1、INV2)的驱动和停止,使得逆变器电路(INV1、INV2)中的消耗功率变小。(The present disclosure provides a power supply device for arc machining and a control method of the power supply device for arc machining. The driving and stopping of the plurality of inverter circuits (INV1, INV2) are selected based on the measured values of the temperatures of the switching elements constituting the inverter circuits (INV1, INV2) and the set values related to the output currents, so that the power consumption in the inverter circuits (INV1, INV2) is reduced.)

1. A power supply device for arc machining, which performs short-circuit welding or pulse welding on a workpiece, comprising:

a first primary rectifier circuit for rectifying commercial ac power and outputting dc voltage;

a 1 st smoothing capacitor for smoothing the dc voltage output from the 1 st primary rectifier circuit;

a 1 st inverter circuit that converts the dc voltage smoothed by the 1 st smoothing capacitor into a high-frequency ac voltage;

a 1 st main transformer for converting the output of the 1 st inverter circuit into a high-frequency AC voltage suitable for arc machining;

a 1 st secondary rectifier circuit for rectifying the output of the 1 st main transformer;

a first rectifier circuit 2 that rectifies the commercial ac power and outputs a dc voltage;

a 2 nd smoothing capacitor for smoothing the dc voltage output from the 2 nd primary rectifier circuit;

a 2 nd inverter circuit that converts the dc voltage smoothed by the 2 nd smoothing capacitor into a high-frequency ac voltage;

a 2 nd main transformer for converting the output of the 2 nd inverter circuit into a high-frequency alternating voltage suitable for arc machining;

a second rectifier circuit 2 for rectifying the output of the 2 nd main transformer;

a dc reactor that smoothes a current obtained by superimposing an output of the 1 st secondary rectifier circuit and an output of the 2 nd secondary rectifier circuit, and outputs an output current to an output terminal;

an output current detection circuit that detects the output current;

an output current setting circuit that sets a predetermined set value relating to the output current;

a 1 st storage circuit for storing in advance a minimum number of inverter circuits to be driven corresponding to the output current;

a comparison circuit configured to compare a set value related to the output current set by the output current setting circuit with the minimum number of inverter circuits that need to be driven and are corresponding to the output current stored in the 1 st storage circuit, and to obtain the minimum number of inverter circuits that need to be driven and are corresponding to the set value;

a 2 nd storage circuit which stores in advance a relationship of power consumption with respect to temperature, the relationship being a relationship between a temperature of a switching element constituting the inverter circuit, an inverter output current of the inverter circuit for each driving, and power consumption of the inverter circuit;

a set value relating to the output current set by the output current setting circuit;

an arithmetic circuit for obtaining power consumption for a combination of driving and stopping of each inverter circuit based on a measured temperature of a switching element constituting the 1 st inverter circuit, a measured temperature of a switching element constituting the 2 nd inverter circuit, and a relationship between the power consumption and the temperature stored in the 2 nd storage circuit;

a selection circuit that selects a combination of inverter circuits that is equal to or greater than the minimum number of inverter circuits that need to be driven corresponding to the setting, the inverter circuits being obtained by the comparison circuit, and that consumes the least power among the power consumptions obtained by the calculation circuit; and

and an output control circuit that outputs a 1 st output control signal for controlling the 1 st inverter circuit and a 2 nd output control signal for controlling the 2 nd inverter circuit, based on the combination of inverter circuits selected by the selection circuit.

2. The power supply apparatus for arc machining according to claim 1,

the short-circuit welding has a welding start period, a main welding period and a welding end period,

in the main welding period, an average output current, which is a time average of the output current output to the work, is set as a set value of the output current.

3. The power supply apparatus for arc machining according to claim 1,

the pulse welding has a welding start period, a main welding period and a welding end period,

in the main welding period, the base current value and the peak current value are set as set values for the output current.

4. The power supply apparatus for arc machining according to claim 2 or 3, wherein,

in the welding start period, a welding start current value at which welding is started is set as a set value relating to the output current.

5. The power supply apparatus for arc machining according to claim 2 or 3, wherein,

in the welding end period, a welding end current value used for ending welding is set as a set value relating to the output current.

6. A method for controlling a power supply device for arc machining, which is provided with a plurality of inverter circuits connected in parallel and performs short-circuit welding having a welding start period, a main welding period, and a welding end period on a workpiece,

in the method for controlling the power supply device for arc machining,

in the main welding period of the short-circuit welding, power consumption in a combination of operations of the inverter circuits is calculated based on a measured value of a temperature of a switching element constituting the inverter circuit and an average output current which is a time average of output currents output to the work piece,

the respective driving and stopping of the plurality of inverter circuits are selected so that the total of the power consumption in the plurality of inverter circuits is minimized.

7. A method for controlling a power supply device for arc machining, which is provided with a plurality of inverter circuits in parallel and performs pulse welding having a welding start period, a main welding period, and a welding end period on a workpiece,

in the method for controlling the power supply device for arc machining,

calculating power consumption in a combination of operations of the inverter circuits based on a measured value of a temperature of a switching element constituting the inverter circuit, and a base current and a peak current of the pulse welding during the main welding period of the pulse welding,

the respective driving and stopping of the plurality of inverter circuits are selected so that the total of the power consumption in the plurality of inverter circuits is minimized.

8. The method for controlling a power supply apparatus for arc machining according to claim 6 or 7, wherein,

calculating power consumption in a combination of operations of the inverter circuits based on a measured value of a temperature of a switching element constituting the inverter circuit and a constant start current or an average start current obtained by time-averaging an output current in the welding start period,

the respective driving and stopping of the plurality of inverter circuits are selected so that the total of the power consumption in the plurality of inverter circuits is minimized.

9. The method for controlling a power supply apparatus for arc machining according to claim 6 or 7, wherein,

calculating power consumption in a combination of operations of the inverter circuits based on a measured value of a temperature of a switching element constituting the inverter circuit and a constant tail current or an average tail current obtained by time-averaging an output current in the welding end period,

the respective driving and stopping of the plurality of inverter circuits are selected so that the total of the power consumption in the plurality of inverter circuits is minimized.

Technical Field

The present disclosure relates to a technique for performing parallel operation by arranging a plurality of inverter circuits in parallel in a power supply device for arc machining.

Background

In a power supply device for arc machining, in order to increase an output current as a welding current, a plurality of inverter circuits are provided in parallel to perform a parallel operation.

On the other hand, in the power supply device for arc machining in which a plurality of inverter circuits as described above are provided in parallel, when the output current is small in particular, there is a case where weldability is improved by stopping some of the inverter circuits as compared with driving all of the inverter circuits.

In a conventional power supply device for arc machining in which a plurality of inverter circuits are connected in parallel, there is disclosed a method of detecting missing teeth in a pulse waveform of an output control signal of an inverter circuit and stopping one of the inverter circuits (patent document 1).

Prior art documents

Patent document

Patent document 1: japanese patent No. 4965238

Disclosure of Invention

However, in the above-described conventional configuration, the power consumption of the entire arc machining power supply apparatus may be increased by stopping any inverter circuit.

The present disclosure provides a method for controlling a reduction in power consumption of an arc machining power supply device in which a plurality of inverter circuits are provided in parallel.

An aspect of the present disclosure provides a power supply device for arc machining that performs short-circuit welding or pulse welding on a workpiece, the power supply device including: a first primary rectifier circuit for rectifying commercial ac power and outputting dc voltage; a 1 st smoothing capacitor for smoothing the DC voltage outputted from the 1 st primary rectifier circuit; a 1 st inverter circuit for converting the DC voltage smoothed by the 1 st smoothing capacitor into a high-frequency AC voltage; a 1 st main transformer for converting the output of the 1 st inverter circuit into a high-frequency AC voltage suitable for arc machining; a 1 st secondary rectification circuit for rectifying the output of the 1 st main transformer; a first rectifier circuit 2 for rectifying commercial ac power and outputting dc voltage; a 2 nd smoothing capacitor for smoothing the DC voltage outputted from the 2 nd primary rectifier circuit; a 2 nd inverter circuit for converting the dc voltage smoothed by the 2 nd smoothing capacitor into a high-frequency ac voltage; a 2 nd main transformer for converting the output of the 2 nd inverter circuit into a high frequency AC voltage suitable for arc machining; a second rectifier circuit 2 for rectifying the output of the 2 nd main transformer; a dc reactor that smoothes a current obtained by superimposing an output of the 1 st secondary rectifier circuit and an output of the 2 nd secondary rectifier circuit, and outputs an output current to an output terminal; an output current detection circuit for detecting an output current; an output current setting circuit that sets a predetermined set value relating to the output current; a 1 st storage circuit for storing in advance a minimum number of inverter circuits to be driven corresponding to the output current; a comparison circuit for comparing a set value related to the output current set by the output current setting circuit with the minimum number of inverter circuits required to be driven corresponding to the output current stored in the 1 st storage circuit, and obtaining the minimum number of inverter circuits required to be driven corresponding to the setting; a 2 nd storage circuit which stores in advance a relationship of power consumption with respect to temperature, the relationship being a relationship between a temperature of a switching element constituting the inverter circuit, an inverter output current of the inverter circuit for each driving, and power consumption of the inverter circuit; a set value related to the output current set by the output current setting circuit; an arithmetic circuit for obtaining power consumption for a combination of driving and stopping of each inverter circuit based on a relationship between a measured temperature of a switching element constituting the 1 st inverter circuit, a measured temperature of a switching element constituting the 2 nd inverter circuit, and power consumption stored in the 2 nd storage circuit with respect to temperature; a selection circuit that selects a combination of inverter circuits that are not less than the minimum number of inverter circuits that need to be driven according to the setting obtained by the comparison circuit and that consume the least power among the power consumptions obtained by the calculation circuit; and an output control circuit that outputs a 1 st output control signal for controlling the 1 st inverter circuit and a 2 nd output control signal for controlling the 2 nd inverter circuit, based on the combination of the inverter circuits selected by the selection circuit.

A control method of a power supply device for arc machining according to another aspect of the present disclosure is a control method of a power supply device for arc machining in which a plurality of inverter circuits are provided in parallel and short-circuit welding having a welding start period, a main welding period, and a welding end period is performed on a workpiece, wherein, in the main welding period of the short-circuit welding, power consumption in a combination of operations of the respective inverter circuits is calculated based on a measured value of a temperature of a switching element constituting the inverter circuits and an average output current that is a time average of output currents output to the workpiece, and driving and stopping of the plurality of inverter circuits are selected so that a total of power consumption of the respective inverter circuits is minimized.

A control method of a power supply device for arc machining according to still another aspect of the present disclosure is a control method of a power supply device for arc machining in which a plurality of inverter circuits are provided in parallel and pulse welding having a welding start period, a main welding period, and a welding end period is performed on a work, and with respect to the main welding period of the pulse welding, power consumption in a combination of operations of the respective inverter circuits is calculated based on a measured value of a temperature of a switching element constituting the inverter circuits, and a base current and a peak current of the pulse welding, and driving and stopping of each of the plurality of inverter circuits is selected so that a total of the power consumption in the plurality of inverter circuits is minimized.

A power supply device for arc machining according to an aspect of the present disclosure is a power supply device for arc machining that is capable of handling a large current, the power supply device including a plurality of power supply units connected in parallel. Each power supply unit includes a primary rectification circuit, a smoothing capacitor, an inverter circuit, a main transformer, and a secondary rectification circuit. The arc machining power supply device measures the temperatures of switching elements constituting each inverter circuit, and determines the driving or stopping of each inverter circuit based on the temperatures, so that the power consumption in each inverter circuit is minimized. Therefore, the power consumption of the power supply device for arc machining can be reduced.

Drawings

Fig. 1 is an electrical connection diagram of a power supply device for arc machining in which two power supply units are provided in parallel.

Fig. 2 is a diagram showing an example of information stored in the 1 st storage circuit in the power supply device for arc machining in which two power supply units are provided in parallel, that is, an example of a relationship between the minimum number of inverter circuits that need to be driven in accordance with an output current.

Fig. 3A is a diagram showing an example of information stored in the 2 nd memory circuit in the power supply device for arc machining in which two power supply units are provided in parallel, that is, an example of a relationship between power consumption and temperature, and more specifically, an example of a relationship between inverter output current of an inverter circuit and power consumption of the inverter circuit, which is driven on an average per temperature basis of the inverter circuit.

Fig. 3B is a diagram showing another example of the relationship between the consumed power and the temperature.

Fig. 4 is a diagram showing an example of the calculation result of the calculation circuit in the power supply device for arc machining in which two power supply units are provided in parallel.

Fig. 5 is a diagram showing an example of an output current waveform and an output voltage waveform at the time of short-circuit welding.

Fig. 6A is a diagram showing power consumption of the inverter circuit in a normal temperature region with respect to a combination of driving and stopping of each inverter circuit.

Fig. 6B is a diagram showing power consumption of the inverter circuit in a high temperature region with respect to a combination of driving and stopping of each inverter circuit.

Fig. 7 is a diagram showing the operation result of the operation circuit.

Fig. 8 is a diagram showing an example of the relationship between the output current and the output voltage and the number of inverter circuits to be driven during short-circuit welding.

Fig. 9 is a diagram showing an example of the relationship between the output current and the output voltage and the number of inverter circuits to be driven during short-circuit welding.

Fig. 10 is a diagram showing an example of an output current waveform and an output voltage waveform at the time of pulse welding.

Fig. 11 is a diagram showing an example of the relationship between the output current and the output voltage during pulse welding and the number of inverter circuits to be driven.

Detailed Description

(embodiment mode 1)

Hereinafter, embodiment 1 of the present disclosure will be described with reference to fig. 1 to 9. First, the configuration of the power supply device for arc machining will be described with reference to fig. 1 to 4. Fig. 1 shows a power supply device for arc machining in which two power supply units each including a primary rectifier circuit, a smoothing capacitor, an inverter circuit, a main transformer, and a secondary rectifier circuit are connected in parallel.

A dc power supply circuit is formed by a first primary rectifier circuit DR11 that rectifies AC power from a commercial AC power supply AC and outputs a dc voltage, and a first smoothing capacitor C1 that smoothes the dc voltage. The 2 nd primary rectifier circuit DR12 and the 2 nd smoothing capacitor C2 are provided in parallel with the 1 st primary rectifier circuit DR11, and perform the same operations as the 1 st primary rectifier circuit DR11 and the 1 st smoothing capacitor C1 that smoothes the dc voltage, respectively.

The 1 st inverter circuit INV1 is formed of switching elements such as IGBTs and MOSFETs. The 1 st inverter circuit INV1 converts the dc voltage output from the 1 st primary rectifier circuit DR11 into a high-frequency ac voltage and outputs the high-frequency ac voltage. The 2 nd inverter circuit INV2 also converts the dc voltage output from the 2 nd primary rectifier circuit DR12 into a high-frequency ac voltage and outputs the high-frequency ac voltage.

The 1 st main transformer MTR1 converts the high-frequency ac voltage output from the 1 st inverter circuit INV1 into a high-frequency ac voltage suitable for arc machining. The 1 st secondary rectifier circuit DR21 rectifies the output of the 1 st main transformer MTR1 to output a direct current.

The 2 nd main transformer MTR2 converts the high-frequency ac voltage output from the 2 nd inverter circuit INV2 into a high-frequency ac voltage suitable for arc machining. The 2 nd secondary rectifier circuit DR22 rectifies the output of the 2 nd main transformer MTR2 to output a direct current.

The dc reactor DCL smoothes a dc current obtained by superimposing a dc current output from the 1 st secondary rectifier circuit DR21 and a dc current output from the 2 nd secondary rectifier circuit DR 22.

Electric wires and the like that can be electrically connected by an operator are attached between the output terminal OT and the welding torch TH and between the output terminal OT and the workpiece M, respectively. The output terminal OT supplies the dc current smoothed by the dc reactor DCL as a welding current between the welding torch TH and the workpiece M.

The output current detection circuit CT detects an output current as a welding current and outputs an output current detection signal Io indicating the detected output current. The output current is a direct current obtained by superimposing a direct current outputted from the 1 st secondary rectifier circuit DR21 and a direct current outputted from the 2 nd secondary rectifier circuit DR 22.

The output current setting circuit IS outputs a set value relating to an output current previously adjusted by an operator as an output current setting signal IS.

The 1 st storage circuit MC1 stores in advance a relationship of the minimum number of inverter circuits that need to be driven with respect to the minimum output current. Here, the inverter circuits refer to a 1 st inverter circuit INV1 and a 2 nd inverter circuit INV 2. The 1 st storage circuit MC1 outputs the stored relationship as a 1 st storage signal MC 1. For example, as shown in fig. 2, the 1 st storage circuit MC1 stores the relationship of the minimum number of inverter circuits that need to be driven corresponding to the output current. In the case where the output current is a current value smaller than the output current threshold Ith, at least one inverter circuit needs to be driven. When the output current is equal to or larger than the output current threshold Ith, at least two inverter circuits need to be driven.

The comparison circuit CC shown in fig. 1 compares the output current setting signal Is with the 1 st stored signal Mc1, and outputs the minimum number of inverter circuits to be driven as the comparison signal CC.

The 2 nd storage circuit MC2 stores the relationship between the power consumption of the inverter circuit and the temperature, and outputs the relationship as the 2 nd storage signal MC 2. More specifically, the relationship is a relationship between the inverter output current of each inverter circuit driven on average and the power consumption of the inverter circuit with respect to the temperature of the switching element constituting the inverter circuit. For example, the 2 nd storage circuit MC2 stores the relationship between the inverter output current of each inverter circuit driven on average and the power consumption of the inverter circuit with respect to temperature as shown in fig. 3A. As is clear from this figure, when the output current per inverter circuit to be driven is increased on average, the power consumption of the inverter circuit tends to be increased. In addition, when the temperature range is a high temperature of, for example, 80 to 90 ℃, the slope of the power consumption of the inverter output current per driving inverter circuit increases compared to the normal temperature of 5 to 35 ℃.

Conversely, as shown in fig. 3B, when the temperature range is high, the slope of the power consumption with respect to the inverter output current per driving inverter circuit may be reduced as compared with the normal temperature. The relationship between the power consumption of the inverter circuit stored in the 2 nd memory circuit MC2 and the temperature can be determined by specifications of switching elements (IGBT and MOSFET) constituting the 1 st inverter circuit INV1 and the 2 nd inverter circuit INV2, and the like.

The 1 st temperature measurement value T1 shown in fig. 1 is a temperature measurement value of the switching elements constituting the 1 st inverter circuit INV 1. The 2 nd temperature measurement value T2 is a temperature measurement value of the switching elements constituting the 2 nd inverter circuit INV 2. The temperature of these switching elements is measured by a thermistor or the like, not shown.

The operation circuit OC calculates the total power consumption of all the inverter circuits for the combination of driving and stopping of each inverter circuit. The total power consumption is obtained based on the 1 st temperature measurement value T1, the 2 nd temperature measurement value T2, and the 2 nd memory signal Mc 2. The arithmetic circuit OC outputs the arithmetic result as an arithmetic signal OC. For example, fig. 4 shows the calculation result of the power consumption in the combination of the inverter circuits by the calculation circuit OC. The 1 st inverter circuit INV1 and the 2 nd inverter circuit INV2 are driven and stopped in combination of 3 kinds (except for the case where both are stopped). The computing circuit OC computes power consumption values W21, W22, and W43(W31+ W32), which are the total power consumption Ww3 in each case.

Here, the power consumption value W21 is a value of the total power consumption when the 1 st inverter circuit INV1 is driven and the 2 nd inverter circuit INV2 is stopped, that is, a value of the total power consumption when only one of the 1 st inverter circuit INV1 is driven. The power consumption value W22 is a value of the total power consumption when the 1 st inverter circuit INV1 is stopped and the 2 nd inverter circuit INV2 is driven, that is, a value of the total power consumption when only one of the 2 nd inverter circuit INV2 is driven. Note that the power consumption value W43 is a total power consumption value when the two inverter circuits are driven and the 1 st inverter circuit INV1 and the 2 nd inverter circuit INV2 are driven together, that is, a value of power consumption of the sum of the power consumption values W31 of the 1 st inverter circuit INV1 and the power consumption value W32 of the 2 nd inverter circuit INV 2.

The selection circuit SC shown in fig. 1 selects a combination having the smallest total power consumption of the 1 st inverter circuit INV1 and the 2 nd inverter circuit INV2 among combinations having the smallest number of inverter circuits to be driven. The selection result is obtained based on the comparison signal Cc and the operation signal Oc. The selection circuit SC outputs a selection result regarding driving or stopping of each inverter circuit as a selection signal SC.

The output control circuit OCC controls the output of the inverter circuit selected to be driven by the selection signal Sc so that the output current detection signal Io Is equal to the output current setting signal Is. The output control circuit OCC further controls the output of the inverter circuit selected to be stopped by the selection signal Sc to be 0. The output control circuit OCC outputs a 1 st output control signal Occ1 for controlling the output of the 1 st inverter circuit INV1 and a 2 nd output control signal Occ2 for controlling the output of the 2 nd inverter circuit INV 2.

The 1 st inverter driving circuit SD1 outputs a 1 st inverter driving signal SD1 for driving the 1 st inverter circuit INV1 according to the 1 st output control signal Occ 1. Further, the 2 nd inverter driving circuit SD2 outputs a 2 nd inverter driving signal SD2 for driving the 2 nd inverter circuit INV2 according to the 2 nd output control signal Occ 2.

In this way, in the power supply apparatus for arc machining having the configuration shown in fig. 1, the 1 st storage circuit MC1 stores the relationship of the minimum number of inverter circuits to be driven with respect to the output current shown in fig. 2. The 2 nd storage circuit MC2 stores the relationship between the temperature of the switching elements constituting the inverter circuit, the average inverter output current per driven inverter circuit, and the power consumption of the inverter circuit shown in fig. 3A.

Next, the operation of short-circuit welding, which is short-circuit arc welding, will be described with reference to fig. 5 to 9. The short-circuit welding includes a welding start period Th, a main welding period Tw, and a welding end period Te. The main welding period is a period in which a short-circuit period Ts in a short-circuit state and an arc period Ta in an arc state are repeatedly performed. In the following description, it is assumed that the 1 st inverter circuit INV1 and the 2 nd inverter circuit INV2 are configured by the same switching elements. The same switching elements are switching elements of the same type, in other words, of the same performance.

Fig. 5 shows an output current waveform and an output voltage waveform at the time of short-circuit welding. The main welding period Tw is a period during which the welding torch TH is moved to weld a portion (weld line) to be welded to the workpiece M. The average output current Iw is a current obtained by averaging the output current supplied between the welding wire and the workpiece M in the main welding period Tw, in other words, the output current output from the workpiece M over time. The average output current Iw corresponds to a set current that is a set value of the output current in the main welding period Tw. The welding start period Th is a period in which a start current Ih higher than the average output current Iw in the main welding period Tw is output for a certain time to facilitate start of welding. The welding end period Te is a period in which the tail current Ie lower than the average output current Iw in the main welding period Tw is output for a predetermined time to prevent the wire from sticking to the workpiece M. Basically, the operator adjusts the average output current Iw in the main welding period Tw to weld the workpiece M appropriately.

As described above, the main welding period Tw of the short-circuit welding includes the short-circuit period Ts and the arc period Ta. The short circuit period Ts is a period of a short circuit state in which the welding wire is electrically contacted (short-circuited) with the workpiece M. The arc period Ta is a period of an arc state in which short-circuit is broken and an arc is generated. As shown in fig. 5, in the short-circuit period Ts, the output voltage becomes low. On the other hand, in the arc period Ta, the output voltage increases, and the output current decreases from a high current value. As described above, when the set value of the average output current Iw is constant, the output during the actual welding in the short-circuit welding is constant to some extent although there is some variation.

Therefore, the average output current 1w set by the operator can be treated as the set value of the output current setting signal Is with respect to the main welding period in the short circuit welding. When the set value of the average output current Iw is larger than the output current threshold Ith (see fig. 2) stored in the 1 st memory circuit MC1, the comparison signal Cc indicates the driving of the two inverter circuits. On the other hand, when the set value of the average output current Iw is small with respect to the output current threshold Ith, the comparison signal Cc indicates the driving of at least one inverter circuit. In this case, the minimum number of inverter circuits to be driven is changed based on the 1 st temperature measurement value T1 and the 2 nd temperature measurement value T2.

Here, a case where the set value of the average output current Iw is small with respect to the output current threshold Ith will be described.

For example, fig. 3A shows characteristics of switching elements of an inverter circuit in which a slope of an increase in power consumption in a normal temperature region is smaller than that in a high temperature region. When the average output current per inverter circuit increases, the power consumption of the inverter circuit also tends to increase. In addition, the slope of the increase in power consumption is smaller in the normal temperature region than in the high temperature region. In the normal temperature region, even if the output current per inverter circuit driven on average increases, the rate of increase in power consumption is small.

The high temperature region is a temperature higher than the normal temperature region and at which the switching elements of the inverter circuit are not damaged, and is, for example, a temperature of 80 to 90 ℃. The normal temperature range is, for example, a temperature of 5 to 35 ℃.

Before welding in a state where an inverter circuit of the power supply device for arc machining is in a sufficiently cooled normal temperature region, the 1 st measured temperature value T1 and the 2 nd measured temperature value T2 are set to substantially the same value. In this case, the relationship between the inverter output current and the power consumption of the inverter circuit is, for example, the relationship shown in fig. 6A. Since the temperature of the inverter circuit is in the normal temperature range, the slope of the increase in power consumption of the inverter circuit is small relative to the increase in the inverter output current per driving inverter circuit on average.

Fig. 7 shows the calculation result of the power consumption in the combination mode of the inverter circuits obtained by the calculation circuit OC at this time. The operation circuit OC operates the total power consumption Ww3 of each of the combinations of driving and stopping of the 1 st inverter circuit INV1 and the 2 nd inverter circuit INV 2. Specifically, the arithmetic circuit OC calculates power consumption values Ww11, Ww12, and Ww33(Ww21+ Ww22) as the total power consumption Ww 3.

An inverter output current when the average output current Iw is supplied to the output terminal OT by driving either the 1 st inverter circuit INV1 or the 2 nd inverter circuit INV2 is referred to as an inverter output current I1. Further, an inverter output current of each inverter circuit in a case where two inverter circuits of the 1 st inverter circuit INV1 and the 2 nd inverter circuit INV2 are driven together and the average output current Iw is supplied to the output terminal OT is set as the inverter output current I2. Here, the inverter output current I1 is larger than the inverter output current I2. In addition, when the two inverter circuits are driven together, the outputs of the inverter circuits are made the same. In other words, the inverter output current I1 is about 2 times the inverter output current I2.

The power consumption value Ww11 is a value of the total power consumption when the 1 st inverter circuit INV1 is driven and the 2 nd inverter circuit INV2 is stopped, that is, a value of the total power consumption when only one of the 1 st inverter circuit INV1 is driven. The power consumption value Ww12 is a value of the total power consumption when the 1 st inverter circuit INV1 is stopped and the 2 nd inverter circuit INV2 is driven, that is, a value of the total power consumption when only one of the 2 nd inverter circuits INV2 is driven. The inverter output current per inverter circuit averaged when driven at the power consumption rate values Ww11 and Ww12 is the inverter output current I1.

Note that the power consumption value Ww33 is a value of power consumption that is the sum of power consumption values of the inverter circuits when the two inverter circuits are driven together. That is, when the 1 st inverter circuit INV1 and the 2 nd inverter circuit INV2 are driven together, the power consumption value Ww21 of the 1 st inverter circuit INV1 and the power consumption value Ww22 of the 2 nd inverter circuit INV2 are the sum of the values. The average inverter output current per inverter circuit when driven at the power consumption value Ww21 and the power consumption value Ww22 is the inverter output current I2.

Specifically, the inverter output current I1 is an inverter output current of the inverter circuit to be driven when either the 1 st inverter circuit INV1 or the 2 nd inverter circuit INV2 is driven and a current of the average output current Iw is supplied to the output terminal OT.

The power consumption value Ww11 of the 1 st inverter circuit INV1 is a value of power consumption of the 1 st inverter circuit INV1 when a current of the average output current Iw is supplied to the output terminal OT only through the 1 st inverter circuit INV 1.

A power consumption value Ww12 of the 2 nd inverter circuit INV2 is a value of power consumption of the 2 nd inverter circuit INV2 when a current of the average output current Iw is supplied to the output terminal OT only through the 2 nd inverter circuit INV 2. Under the above conditions, the power consumption value Ww11 of the 1 st inverter circuit INV1 is substantially equal to the power consumption value Ww12 of the 2 nd inverter circuit INV 2.

The inverter output current I2 is an average inverter output current for each inverter circuit when the two inverter circuits are driven together and the current of the average output current Iw is supplied to the output terminal OT. The power consumption value Ww21 of the 1 st inverter circuit INV1 is a value of power consumption of the 1 st inverter circuit INV1 when two inverter circuits including the 1 st inverter circuit INV1 and the 2 nd inverter circuit INV2 supply an average output current Iw to the output terminal OT.

Note that the power consumption value Ww22 of the 2 nd inverter circuit INV2 is a value of power consumption of the 2 nd inverter circuit INV2 when the two inverter circuits including the 1 st inverter circuit INV1 and the 2 nd inverter circuit INV2 supply the average output current Iw to the output terminal OT. Under the above conditions, the power consumption value Ww21 of the 1 st inverter circuit INV1 is substantially equal to the power consumption value Ww22 of the 2 nd inverter circuit INV 2.

The power consumption value Ww33 is the total power consumption of the two inverter circuits when the two inverter circuits including the 1 st inverter circuit INV1 and the 2 nd inverter circuit INV2 collectively supply the average output current Iw to the output terminal OT. The value of the consumed power is the sum of a consumed power value Ww21 of the 1 st inverter circuit INV1 and a consumed power value Ww22 of the 2 nd inverter circuit INV 2.

Here, the total power consumption Ww3 of the calculation result of the calculation circuit OC for the combination of driving and stopping of each inverter circuit is as shown in fig. 7. Fig. 6A shows power consumption of the inverter circuit in the normal temperature region where the temperature of the switching element is low. In this case, for example, the combination of the operations of the inverter circuit in which the power consumption of the inverter circuit is reduced at the time of short-circuit welding is as follows.

Specifically, the power consumption value Ww33 is larger than the power consumption value Ww11 and larger than the power consumption value Ww 12.

Therefore, the selection circuit SC selects one inverter circuit in the normal temperature range, reduces the power consumption of the arc machining power supply device, and outputs the selection signal SC for supplying the average output current Iw to the output terminal OT.

In this example, it is assumed that the 1 st temperature measurement value T1 is substantially equal to the 2 nd temperature measurement value T2. Therefore, when only one of the inverter circuits is driven alone, the power consumption value Ww11 of the 1 st inverter circuit INV1 is substantially equal to the power consumption value Ww12 of the 2 nd inverter circuit INV 2. However, the selection signal Sc is actually output to drive one of the smaller inverter circuits.

As a result, in the normal temperature region where the temperature of the switching element of the inverter circuit is low, the relationship between the inverter output current and the output voltage at the time of short-circuit welding and the number of inverter circuits to be driven is shown in fig. 8. One inverter circuit is driven during each of the main welding period Tw and the welding end period Te. In the welding start period Th, the inverter output current is larger than the output current threshold Ith, and therefore, the two inverter circuits are driven.

In addition, for example, after one inverter circuit is driven in the main welding period Tw or the like, the temperature of the switching elements constituting the 1 st inverter circuit INV1 and the 2 nd inverter circuit INV2 similarly rises, and becomes a high temperature region. In the case of the characteristics of the switching elements shown in fig. 3A, when the temperature of the switching elements rises to reach a high temperature range, the increase rate, that is, the increase gradient of the power consumption with respect to the average output current per inverter circuit to be driven, becomes large.

As described above, the temperature of the switching elements of the inverter circuit is in a high temperature range, and the relationship between the inverter output current and the power consumption of the inverter circuit per inverter circuit to be driven on average is as shown in fig. 3A, and the increase gradient of the power consumption in the high temperature range is larger than that in the normal temperature range. In this case, the relationship between the average inverter output current per inverter circuit and the power consumption of the inverter circuit in the high temperature region is as shown in fig. 6B.

Specifically, in the 1 st inverter circuit INV1 and the 2 nd inverter circuit INV2, the power consumption value at the time of driving either one is set as the power consumption value (Ww11, Ww 12). The power consumption value, which is the sum of the power consumption values (Ww21, Ww22) when the two inverter circuits are driven together, is defined as a power consumption value Ww 33. As shown in fig. 6B, the slope of the power consumption of the inverter circuit with respect to the average inverter output current per driven inverter circuit is larger than the relationship in the normal temperature region shown in fig. 6A.

In the high temperature region, the total power consumption Ww3 of the calculation result of the calculation circuit OC in the combined mode of driving and stopping the inverter circuits is as shown in fig. 7. The combination of the inverter circuits itself does not change from the normal temperature region before the temperature rise. When the power consumption of the inverter circuit in the high temperature region where the temperature of the switching element is high is in the relationship shown in fig. 6B, for example, the combination of the operations of the inverter circuit in which the power consumption of the inverter circuit is reduced at the time of short-circuit welding is as follows.

Specifically, the consumed power value Ww33 is smaller than the consumed power value Ww11 or the consumed power value Ww 12.

Therefore, the selection circuit SC drives the two inverter circuits together, reduces the power consumption of the arc machining power supply device, and outputs the selection signal SC for supplying the average output current Iw to the output terminal OT.

As a result, when welding is resumed in a high temperature region where the temperature rises, the relationship between the output current and the output voltage at the time of short-circuit welding and the number of inverter circuits to be driven is shown in fig. 9, for example. During the actual welding period Tw and the welding end period Te in which the temperature of the switching element rises, the two inverter circuits are driven. In the welding start period Th, the inverter output current is larger than the output current threshold Ith, and therefore, the two inverter circuits are driven.

As described above, the power supply device for arc machining according to the present embodiment includes a plurality of inverter circuits (INV1, INV2) provided in parallel, and performs short-circuit welding on the workpiece M. The short-circuit welding has a welding start period Th, a main welding period Tw, and a welding end period Te. In the main welding period Tw of short-circuit welding, the power supply device for arc machining calculates power consumption in a combination of operations of driving and stopping the inverter circuits (INV1 and INV2) based on temperature measurement values (T1 and T2) of switching elements constituting the inverter circuits (INV1 and INV2) and an average output current Iw which is a time average of output currents of welding currents output to the workpiece M. The arc machining power supply device selects the driving and stopping of each of the plurality of inverter circuits so that the total power consumption Ww3, which is the sum of the power consumptions of the plurality of inverter circuits (INV1, INV2), is minimized.

This reduces power consumption of inverter circuits (INV1, INV2) constituting the power supply device for arc machining in the main welding period Tw in short-circuit welding.

(embodiment mode 2)

Next, embodiment 2 of the present disclosure will be described with reference to fig. 1 to 3A and 10 to 11.