WO2025048132A1 - Inverter-type proportional control microwelding device - Google Patents

Abstract

The present invention relates to an inverter-type proportional control microwelding device and, more specifically, to an inverter-type proportional control microwelding device that can perform a hot start regulation function and an anti-stuck function while using the difference between an output current and a target current as a tracking error and performing proportional control so that the error converges to zero. The inverter-type proportional control microwelding device according to an embodiment of the present invention comprises: a main body; a welding torch that is linked to the main body and contains an electrode therein; a welding electrode that is linked to the main body and connected to a workpiece to be welded; and a current supply means that is installed inside the main body and applies a welding current to the electrode of the welding torch and the welding electrode.

Description

Inverter type proportional control micro welding device

The present invention relates to an inverter type proportional control micro welding device, and more specifically, to an inverter type proportional control micro welding device capable of controlling hot start and preventing sticking while proportionally controlling the difference between the output current and the target current so that the error converges to zero (0) as a tracking error.

Welding technology used in all industrial fields requires stable power supply of low voltage and high current to the electrode and base material to smoothly generate an arc and improve the welding quality, which is the goal of welding.

Accordingly, with the development of power electronics technology to supply such stable power, AC arc welders, thyristor welders, and inverter welders have been developed in that order.

Although thyristor welders were widely used in the past, their scale is gradually decreasing due to the advent of inverter welders.

This trend is because the inverter's welding quality is superior and the welding machine can be made lighter.

Despite these advantages, inverter control technology is still inadequate and has many problems.

The trends in inverter technology in welding machines are as follows.

For example, in TIG welding machines, a high-frequency generator is used to start the arc.

The method is to break down the insulation between the tungsten electrode and the base metal and then rapidly increase the welding current using an inverter.

In CO2 welders, the voltage and current change simultaneously as the resistance of the welding specimen changes during the welding process.

However, in the case of conventional inverters, the Joule heat changes due to the change in resistance during welding due to the constant current control method, and therefore, the molten pool of the base material splashes a lot due to the change in heat amount, generating spatter.

To solve these problems, there is a trend toward introducing inverters with constant power control. That is, since the constant power control method has an inverse relationship between voltage and current, it maintains a constant current density according to the change in resistance.

This type of static power control method is mainly applied to expensive welding machines, and is not applied to DC-arc welding machines, which are relatively inexpensive and have a high distribution rate, due to cost issues.

In the case of a Brown gas generator, the system is configured by directly applying the inverter of a welding machine.

The reality is that electrolysis tanks are installed on the output terminals of welding systems instead of welding rods and base metals, and this is being generated without any relevant expertise.

Because the Brown's gas generator was manufactured in such a crude manner, there is not even any related literature.

The present invention was created to solve the above-mentioned problems and needs, and the purpose of the present invention is to provide an inverter-type proportional control micro welding device for controlling hot start and preventing sticking while proportionally controlling the difference between the output current and the target current so that the error converges to zero (0) as the tracking error.

In order to achieve the above-mentioned purpose, an inverter-type proportional control micro-welding device according to one embodiment of the present invention includes a main body, a welding torch connected to the main body and having an electrode provided therein, a welding electrode connected to the main body and connected to a material to be welded, and a current supply means installed in the main body and supplying current for welding to the electrode of the welding torch and the welding electrode.

In addition, the current supply means includes a power input unit connected to commercial AC current, a first rectifier unit that rectifies AC current input from the power input unit into DC current, a smoothing unit that smoothes DC current output from the first rectifier unit, an inverter unit that converts the DC current smoothed by the smoothing unit into variable high-frequency AC current, a transformer unit that transforms AC current output from the inverter unit into low-voltage, high-current suitable for welding, a second rectifier unit that rectifies AC current output through the transformer unit again and converts it into DC voltage, an output terminal that is connected to an electrode of the welding torch and a welding electrode to output (+) output and (-) output, and a control unit that controls the overall operation of the current supply means and performs hot start control and anti-stuck prevention through a proportional controller.

According to the present invention, there is an advantage in that welding can be easily performed by not only experts but also ordinary people by providing a hot-start function to facilitate arc generation at the start of welding.

In addition, the anti-stuck function can be implemented to prevent short circuits between the base material and the welding rod that may occur during the welding process, thereby increasing the ease of work.

In addition, the inverter-type welding device proposed by the present invention has the advantage of being able to greatly contribute to the welding industry by improving welding quality, reducing welding costs, and increasing welding productivity by controlling welding output current.

FIG. 1 is a perspective view illustrating an inverter-type proportional control micro welding device according to one embodiment of the present invention.

Figure 2 is a circuit diagram illustrating a current supply means according to one embodiment of the present invention.

FIG. 3 is an exemplary time chart for an IGBT among the configurations of a current supply means according to one embodiment of the present invention.

FIGS. 4 to 15 are graphs and flowcharts for explaining an inverter-type proportional control micro welding device according to an embodiment of the present invention.

The present invention may have various modifications and embodiments, and specific embodiments are illustrated in the drawings and described in detail in the detailed description.

However, this is not intended to limit the present invention to specific embodiments, but should be understood to include all modifications, equivalents, or substitutes included in the spirit and technical scope of the present invention.

When it is said that a component is "connected" or "connected" to another component, it should be understood that it may be directly connected or connected to that other component, but there may also be other components in between.

On the other hand, when it is said that a component is "directly connected" or "directly connected" to another component, it should be understood that there are no other components in between.

The terminology used in this specification is only used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise.

In this specification, it should be understood that the terms “include” or “have”, etc., are intended to specify the presence of a feature, number, step, operation, component, part or combination thereof described in the specification, but do not exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts or combinations thereof.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only to distinguish one component from another.

Additionally, terms such as “unit” described in the specification mean a unit that processes at least one function or operation, which may be implemented by hardware, software, or a combination of hardware and software.

In addition, it is to be understood that components of the embodiments described with reference to each drawing are not limited to the embodiments described herein, but may be implemented to be included in other embodiments within the scope in which the technical spirit of the present invention is maintained, and may also be reimplemented as one embodiment in which multiple embodiments are integrated, even if a separate description is omitted.

In addition, when explaining with reference to the attached drawings, identical components are given identical or related reference symbols regardless of the drawing symbols, and redundant descriptions thereof are omitted.

In describing the present invention, if it is determined that a detailed description of a related known technology may unnecessarily obscure the gist of the present invention, the detailed description will be omitted.

FIG. 1 is a perspective view illustrating an inverter-type proportional control micro welding device according to an embodiment of the present invention, FIG. 2 is a circuit configuration diagram illustrating a current supply means according to an embodiment of the present invention, FIG. 3 is an exemplary time chart for an IGBT among the configurations of the current supply means according to an embodiment of the present invention, and FIGS. 4 to 15 are graphs and flowcharts for explaining an inverter-type proportional control micro welding device according to an embodiment of the present invention.

Referring to the drawings described above, an inverter-type proportional control micro welding device (100) according to embodiments of the present invention includes a main body (110), a welding torch (120) connected to the main body (110) and having an electrode provided therein, a welding electrode (130) connected to the main body (110) and connected to a material to be welded (BM), and a current supply means (200) installed in the main body (110) and supplying current for welding to the electrode of the welding torch (120) and the welding electrode (130).

In addition, the current supply means (200) comprises a power input unit (210) connected to commercial AC current from the outside, a first rectifier (220) that rectifies the AC current input from the power input unit (210) into DC current, a smoothing unit (230) that smoothes the DC current output from the first rectifier (220), an inverter unit (240) that converts the DC current smoothed by the smoothing unit (230) into variable high-frequency AC current, a transformer unit (250) that transforms the AC current output from the inverter unit (240) into a low-voltage, high-current suitable for welding, a second rectifier unit (260) that rectifies the AC current output through the transformer unit (250) again and converts it into a DC voltage, and a second rectifier unit (260) that is connected to the electrode of the welding torch (120) and the welding electrode (130) and outputs (+) output and (-) output. It includes a control unit (280) that controls the overall operation of the output terminal (270) and the current supply means (200), and performs hot start and anti-stuck through a proportional controller (282).

In addition, the relationship between the control unit (280) and the output current (i _out ) according to the control signal of the microprocessor (281) is derived as the following arithmetic expressions (1), (2), and (3).

Arithmetic expression (1)

Arithmetic expression (2)

Arithmetic expression (3)

(Here, i _out is the output current, e is the natural constant or Euler's number, u is the control signal, P _w is the PWM duty ratio (%), 0 ≤ P _w ≤ 0.4)

In addition, the proportional controller (282)

의 산술식을 만족한다.If the tracking error (ε) is i _ref - i _out ,

Satisfies the arithmetic expression.

(where, i _ref is the target current, i _out is the output current, u is the control signal, T _i is the integration time [sec], K _p is the proportional gain [A ^-1 ], and K _I is the integral gain [A ^-1 ])

Additionally, the above i _ref corresponds to the target current of hot start or anti-stuck.

In addition, the inverter unit (240) measures voltage and current, and if the measured current and voltage are different from the set values, operates the proportional controller (282) to follow the set current and set voltage.

In addition, the control unit (280) satisfies the following arithmetic expression that generates a current that is 0 to 50 [A] higher than the set welding output current depending on the value of the hot start control volume (%) to facilitate arc formation during the hot start function.

i _{Hot_start ref} = i _setting + 50×Hot start control volume×

(Here, i _{Hot_start ref} is the target welding current to which the hot start function is applied at the start of welding, i _setting is the set welding current determined by the user, and t _ht is the time from the point in time when the hot start function is activated.)

In addition, when the control unit (280) measures the voltage between the welding torch (120) and the material to be welded ((BM)) in real time during the anti-stuck function and drops below the reference voltage (Vmin), the following arithmetic equation is satisfied so as to increase the welding output current by 15 [A] more than the point at which the welding output voltage drops.

i _{stuck_ref} = i _setting + 15×

(Here, i _{stuck_ref} is the target welding output current when the anti-stuck function is in effect, and the set welding output current is 140 [A])

First, in the present invention, a PI controller is applied to make the error zero (0) by using the difference between the output current and the target current as the tracking error.

The control system developed to implement these controllers is based on a microcontroller to implement current control and various functions.

It compares the signal coming through the current measuring sensor with the target current, detects the error, and uses this to control the output current.

Second, various functions were implemented in the welder according to the user's needs.

In the case of welding machines, a hot-start function was provided to facilitate arc generation when starting welding.

This feature helps start welding more easily than with conventional welders by starting welding with a current that is 0 to 40 amperes [A] higher than the target current when starting welding.

Additionally, it has an anti-stuck function.

This function measures the voltage between the base material and the welding electrode during welding, and momentarily increases the welding current by 15 amperes [A] when the base material and the welding electrode become close to each other, thereby preventing a short circuit between the base material and the welding electrode.

In systems like this, the application of microprocessors has made it possible to implement a variety of functions and achieve high precision at the same cost as conventional systems.

Then, the configuration and operation of the inverter type proportional control micro welding device (100) according to one embodiment of the present invention will be described in detail as follows.

Figure 1 is a diagram showing the overall structure of an inverter-type proportional control micro welding device according to one embodiment of the present invention.

An inverter-type proportional control micro welding device (100) according to one embodiment of the present invention is a device that provides a high current between an electrode of a welding torch (120) and a welding electrode (130) to melt a welding rod (not shown) and weld a material to be welded.

As illustrated in FIG. 1, the welding device (100) proposed by the present invention includes a main body (110), a welding torch (120) connected to the main body (110) and having an electrode provided therein, a welding electrode (130) connected to the main body (110) and connected to a material to be welded, and a current supply means (200) installed in the main body (110) and supplying current for welding to the electrode of the welding torch (120) and the welding electrode (130).

Here, the main body (110) forms a body frame of a welding device (100) according to one embodiment of the present invention, and forms an installation frame of an electrode of a welding torch (120), a welding electrode (130), and a current supply means (200).

A welding torch (120) is electrically connected and fixed to the front lower side of the main body (110).

An electrode is provided within the welding torch (120). The electrode of the welding torch (120) forms a welding electrode for welding the material to be welded together with the welding electrode (130). The electrode may form a welding rod itself or may be formed separately from the welding rod.

A welding electrode (130) is electrically connected to the front lower side of the main body (110).

The welding electrode (130) is intended to contact the material to be welded so that welding current can flow to the material to be welded, and includes a connecting member in the form of a pair of tongs or a fastening plate at one end.

Since the above main body (110), welding torch (120) and welding electrode (130) are identical or similar to the configuration of a general welding machine, a detailed description thereof will be omitted in the present invention.

Additionally, an inverter-type current supply means (200) for applying welding current is installed within the main body (110).

It serves to supply current from an inverter-type current supply means (200) and to apply current for welding to the electrode of a welding torch (120) and the welding electrode (130). A circuit configuration diagram of this inverter-type current supply means (200) is shown in Fig. 2.

The inverter-type current supply means (200), as illustrated in FIG. 2, comprises a power input unit (210) that supplies commercial alternating current (AC), a first rectifier (220) that rectifies the alternating current input from the power input unit (210) into direct current, a smoothing unit (230) that smoothes the direct current output from the first rectifier (220), an inverter unit (240) that converts the direct current smoothed by the smoothing unit (230) into variable high-frequency alternating current, a transformer unit (250) that transforms the alternating current output from the inverter unit (240) into a low-voltage, high-current suitable for welding, a second rectifier unit (260) that rectifies the alternating current output through the transformer unit (250) again and converts it into a direct current voltage, and a power supply unit (260) that is connected to a base material (BM) and a welding torch (TC) and outputs (+) output and (-) output. It includes an output terminal (270) and a control unit (280) that controls the overall operation of the inverter type current supply unit (200).

The power input section (210) is connected to a wiring line to receive general commercial alternating current (AC) and inputs commercial power (AC) 380 V or 220 V 60 Hz.

The first rectifier (220) receives commercial power (AC) 380 V or 220 V 60 Hz input from the power input unit (210) and converts it into direct current for use as an inverter, rectifying the AC current input in three phases into direct current.

The first rectifier (220) is a full-wave rectifier that uses the characteristic that current flows only in one direction from the anode (+) to the cathode (-) of the diode, so that only the potential on the (+) side of the AC current passes through, and the potential on the opposite side is pulled up to the (+) side by the diode connected to the other side.

The first rectifier (220) is called a pulse current when only the (+) side is concentrated, and when a capacitor that smoothes this is connected, a direct current (DC) can be obtained.

Additionally, the first rectifier (220) may be formed as a full-wave rectifier bridge circuit including four diodes according to an embodiment.

The smoothing unit (230) can be implemented as a smoothing capacitor connected to the output unit of the first rectifier (220) to rectify or detect the pulsating current output from the first rectifier (220) and output it as a direct current.

The inverter unit (240) converts the direct current smoothed by the smoothing unit (230) into a variable high-frequency alternating current, and can create an alternating current converted to a high frequency of at least 20 kHz.

That is, the inverter unit (240) converts it into a high-frequency AC voltage and then applies it to the primary side of the transformer unit (250).

In addition, the inverter section (240) can be implemented in a form in which four IGBTs (insulated gate bipolar transistors) are arranged in a full bridge form to convert the smoothed direct current in the smoothing section (240) into a variable high-frequency alternating current through cross switching.

The inverter section (240) explains the switching process of obtaining AC current from DC current using a time chart as follows.

As shown in Fig. 3, it is a full-bridge switching circuit in which Q1 (1/2) and Q2 (1/2) are driven simultaneously, and Q1 (2/2) and Q2 (2/2) are also driven simultaneously.

The direction of current flow changes depending on the time the IGBT is turned on, and an AC output voltage is obtained. By controlling the turn-on time of each IGBT, the size of the output voltage can be changed. This method is PWM (pulse width modulation).

In particular, the inverter unit (240) uses a DSP (Digital Signal Processor) that is one level more advanced than the conventional PLC concept control method to control the rapid response system within a very short time, thereby minimizing the amount of heat input to the welding material while maintaining it uniform, thereby safely welding the thin plate without melting and controlling deformation.

The inverter unit (240) is designed and integrated with a digital processing system that enables control up to 1ms (1/1000 sec), thereby enabling low-distortion precision welding of ultra-thin plates through the operation of a precision automatic control system when performing manual welding as well as automatic welding, and the welding arc is stable in pulse welding mode and can effectively control penetration and heat distribution by changing the speed of high and low currents.

The inverter unit (240) developed in the present invention performs current control and therefore receives current feedback.

Therefore, to measure the current, a Hall sensor is used to measure the current.

The Hall CT (Current Transformer) has the advantage of being separated from the power side of the circuit like a conventional Hall element, so that the system is constant, and it can be measured like a differential voltage circuit using resistance, and it has the advantage of having a high frequency of current that can be measured. In addition, it can measure various currents such as alternating current, direct current, and pulse current, so this sensor was selected.

Meanwhile, IGBT is a type of power semiconductor for high-power switching.

The switching function that blocks or allows the flow of electricity can be implemented with other parts or circuits, but products that require precise operation require dedicated parts that operate at a faster speed and have less power loss.

IGBT is a power switching semiconductor that combines the advantages of transistors, which are inexpensive but have complex circuit configurations and slow operating speeds, and MOSFETs, which are expensive but low in power and fast in speed.

The transformer (250) outputs voltage to the secondary side and applies it to the second rectifier (260), and can be implemented as an AC transformer that transforms AC current into low voltage, high current suitable for welding by using the electromagnetic induction phenomenon.

In particular, the transformer (250) can be made smaller and lighter by converting IGBT power at 20 [KHz] or higher, and can be reduced to 1/4 the weight of a conventional welding machine, the size can be reduced to 1/3, and handling and movement can be made easier.

In addition, the transformer (250) uses an insulating transformer to electrically insulate the system and the output section to ensure the safety of the system and the user, and to appropriately lower the output voltage to improve the output characteristics. This insulating transformer uses a high frequency of at least 20 [KHz] to reduce the volume and weight and secure mobility.

Therefore, the transformer (250) for the inverter can adopt an insulating transformer with good high-frequency characteristics.

The transformer (250) is not only useful for high-frequency switching, but also has the advantage of having a higher saturation frequency than an iron core and a size inversely proportional to the frequency when the transformer performs high-speed switching, so it greatly helps in saving energy, reducing weight, and making the system noiseless.

The volume of the transformer (250) at a frequency of 20 [KHz] is reduced to 1/10 compared to that at 50 [Hz].

The second rectifier (260) rectifies the AC current output through the transformer (250) and converts it into a DC voltage, and can be implemented as a known-structure full-wave rectifier bridge circuit including four diodes.

The output terminal (270) is connected to the parent material (BM) and the welding torch (TC), and outputs (+) and (-) outputs of the output converted into direct current (DC) through the second rectifier (260), and welding is performed using the welding torch (TC).

The control unit (280) controls the overall operation of the inverter-type current supply means (200), and also monitors whether abnormal current is supplied through a hall sensor, etc., and controls cleaning control, crater current control, electric shock prevention operation, and operation of a heat dissipation fan.

The control unit (280) proposed by the present invention is a one-chip microprocessor including a microprocessor (281), and has the following characteristics.

Microprocessors (281) are embedded with CPU, ROM, RAM, I/O ports, etc. integrated on the same chip, and are very small in size and inexpensive, so they are used in almost all electronic products.

The microprocessor (281) has built-in PWM, A/D converter, and LCD controller, and is in OTP (One Time Programmable) format.

This format allows the user to program the internal ROM as desired and use it by writing at any time, and is a parallel processing RISC (Reduced Instruction Set Code) structure.

That is, execution and patching are done simultaneously, so the execution speed is fast.

It has a Harvard architecture, so program memory and data memory are clearly separated, and data memory is managed in an integrated manner using a register file, so that the data memory area can be used as if it were a general-purpose register.

In addition, since it is made of CMOS, power consumption is very low (less than 2mA at 5V, 4MHz) and transmission characteristics are excellent. In addition, it has a large noise margin, high integration, and high impedance.

The microprocessor (281) can easily interface with analog signals using an A/D converter, PWM (Pulse Width Modulated) output device, etc.

The control unit (280) was designed to be applicable to various types of systems when implemented.

That is, modules are arranged around the microprocessor (281) to facilitate the addition and deletion of modules according to the system.

The microprocessor (281) and current detection circuit are located at the center of the PCB, the display section, the mounting of which is determined depending on the system, is located at the edge, and the insulation section is located at the bottom of the entire circuit and is designed to maintain a distance from other modules.

The control unit (280) was designed simply by connecting to the outside using a connector.

Therefore, in the present invention, an inverter part (240) is developed by adopting an IGBT having a high switching speed and high internal voltage, thereby contributing to energy saving and miniaturization.

This is information about a controller (282) for causing the output current and voltage coming from the inverter section (240) to follow the target output current and voltage.

The method of controlling the output current by feeding back the output current is obtained based on PI (proportional) control.

To this end, the relationship between the output current and the output signal of the microprocessor (281) is expressed in a formula and used for programming the microprocessor (281).

In addition, this controller (282) was applied to a welding machine, and simulations and experiments were performed to prove its effectiveness.

In the present invention, a system identification method for statistically estimating a model from actual input and output data was used to model the inverter unit (240).

That is, the system was experimentally identified using the relationship between the control signal and the output current in the microprocessor (281).

Figure 4 shows the relationship between the IGBT module driving signal (PWM) and the output current.

This can be expressed as a formula as follows:

(1)

(1)

Here, i _out is the output current, e is the natural constant or Euler number,

P _w is the IGBT driving signal PWM duty ratio (%), 0 ≤ P _w ≤ 0.4.

Figure 5 shows the relationship between the IGBT driving signal (PWM) and the control signal.

40% of the IGBT drive signals are controlled by dividing them into 10 bits.

This can be expressed as a formula as follows:

(2)

(2)

Here, u is a control signal.

Using equations (1) and (2), the relationship between the control input signal and the output current can be derived.

This can be expressed as a formula as follows:

(3)

(3)

Here, i _out is the output current.

Figure 6 is a graph representing equation (3).

The relationship between the control signal input and the welding output current was derived from equations (1) to (3).

In other words, the input and output relationship is expressed in a formula, and this will be applied to the controller.

In the proportional controller (282), the tracking error (ε) is defined as follows.

ε = i _ref -i _out (4)

Here, i _ref is the target output current and corresponds to the target output current when the hot-start and anti-stuck functions are in effect.

That is, it is the target current that the inverter unit (240) must follow.

The PI (proportional) controller (282) is expressed as follows.

(5)

(5)

T _i : integral time of the controller [sec],

K _p : proportional gain of the controller [A ^-1 ],

K _I : Integral gain of the controller [A ^-1 ]

Discrete-time tracking error is defined as follows:

(6)

(6)

i _ref(i) : target current (ith sampling time)

i _out(i) : Output current (ith sampling time)

In the discrete time domain, equation (5) can be expressed as follows.

(7)

(7)

u _i : control signal (i-th sampling time)

ε _i : tracking error (i-th sampling time)

t _d : sampling time,

Here, the sampling time (t _d ) is 15×10 ^-6 seconds [sec].

When t -> ∞, the controller proportional gain and integral gain must be set so that ε -> 0 to complete the controller design.

Proportional gain K _P And the integral gain K _I is,

The system was stable when K _P = 0.7 and K _I = 115.

In equation (7), D(i) is as follows.

(8)

(8)

The above PI controller (282) is applied as in the “A” part of Fig. 2.

The inverter unit (240) proposed by the present invention controls the output current through the PI control described above.

The output current is measured using a signal from the transformer (250), and this signal is compared with the set output current so that the difference, i.e. the tracking error, becomes zero (0).

Figure 7 shows the operating flow diagram of the inverter unit (240).

When the inverter unit (240) first operates, it measures voltage and current, and if the measured current and voltage are different from the set value, the PI controller (282) is operated to follow the set current and voltage.

Next, we move to the function mode, where the functions required by each system are provided. For example, in the case of a welder, the Hot-stat function and Anti-stuck function are provided.

The welding output voltage changes depending on the condition of the arc that occurs during welding.

As the arc length increases, the voltage increases accordingly, and as the arc length decreases, the voltage decreases. If the arc length becomes excessively long, the arc cannot be maintained and extinguishes, preventing further welding.

Conversely, if the arc length becomes shorter, a phenomenon in which the welding rod and base metal stick together (Sruck phenomenon) occurs.

This also prevents further welding and requires the welding rod to be removed.

The welding status according to welding output voltage is summarized in [Table 1].

state voltage Normal welding 7 ~ 35V stuck (Vmin) under 6V Arc disappear (Vmax) over 36V

The present invention is provided with a hot-start function and an anti-stuck function. The flow chart of the hot-start function and the flow chart of the anti-stuck function are expressed in FIG. 8 and FIG. 9.

Figure 8 shows a flow chart of the Hot-start function, which is a function that generates a current that is 0 to 50 amperes [A] higher than the set welding output current depending on the value of the Hot-start control volume (%) to facilitate arc formation.

Expressed as a formula, it is as follows:

(9)i _{Hot_start ref} = i _setting + 50×Value of hot_start volume×

(9)

Here, i _{Hot_start ref} is the target welding current to which the Hot-start function is applied at the start of welding.

i _setting is the set welding current determined by the user.

t _ht means the time from the point when the Hot-start function starts operating.

Figure 9 shows a flow chart of the anti-stuck function.

The anti-stuck function is a function developed to prevent the welding rod from short-circuiting with the base metal and to maintain the arc by increasing the welding output current by 15 amperes [A] more than the point at which the welding output voltage drops when the voltage between the base metal and the welding electrode is measured in real time while welding is in progress and falls below the reference voltage (Vmin).

Expressed as a formula, it is as follows:

(10)i _{stuck_ref} = i _setting + 15×

(10)

Here, i _{stuck_ref} is the target welding output current value that is applied from the moment the voltage drops below the reference voltage (Vmin) during welding, that is, from the moment the Anti_stuck function is executed.

The set welding output current is 140 amperes [A] and the hot-start volume is 60%.

Normal welding voltage is set to Vmax as 36 V and Vmin as 6 V as shown in [Table 1].

Figure 10 is a simulation result of welding output current when the inverter uses the PI controller (282) proposed by the present invention to perform the hot-start function.

By implementing the hot-start function, it can be seen that the welding output current starts at about 20 amperes [A] higher than the set welding output current when welding is started.

Up to 0.5 ms, the target welding output current increased by the hot-start function is followed, and from 1 ms, the set welding output current is reached, showing that stable welding is taking place.

Figure 11 shows the change in the control signal when the hot-start function is performed using the PI controller (282) proposed by the present invention.

A large change in the control signal at the start of welding shows that the control signal changes to generate a high current by the hot-start function.

It shows that there is almost no change in the control input from 0.5 ms and that the target control signal level is reached from 1 ms.

Figure 12 shows the tracking error when the hot-start function is in operation.

It can be seen that the large tracking error at the start of welding is caused by the high welding output current during the hot-start function, and that the tracking error converges to zero (0) as time passes.

Figure 13 is a simulation result of welding output current when the anti-stuck function is operated using the PI controller (282) of the present invention.

When the anti-stuck function is activated, the welding output current follows the target welding output current well and quickly increases to 155 amperes [A], preventing the phenomenon of the welding rod sticking to the base material (Stuck phenomenon). After 1 ms, the set output current is followed well, showing that stable welding is in progress.

Fig. 14 is a result of simulating the change in the control signal when the anti-stuck function is operated using the PI controller (282) of the present invention. At the beginning of the anti-stuck function operation, a high control input is generated to operate the anti-stuck function, and as with the hot-start function, there is almost no change after 0.5 ms, and after 1 ms, it can be seen that the control input becomes stable as the normal welding state is established.

Fig. 15 shows the tracking error when the anti-stuck function is operated when the PI controller (282) is applied. Initially, the tracking error was large because the welding output current was increased for the anti-stuck function, but it can be seen that the tracking error converges to zero (0) as time passes. It can be seen that the tracking error is reduced compared to when the hot-start function is operated because the change is relatively small compared to when the hot-start function is operated.

In this way, the inverter-type proportional control micro welding device (100) according to embodiments of the present invention can expect the following effects.

According to the present invention, one of the greatest advantages of an inverter welder is that it is small and compact, easy to carry, and can be carried like a light-weight briefcase.

Additionally, it has the advantage of consuming less power and can operate on normal household current (commercial current), which saves maintenance costs and thus helps in cost competitiveness.

In addition, since the inverter output power is electronically controlled, it has a wide power adjustment range of up to 100%, so it can be fine-tuned to specific needs, and has the advantage of stable output, enabling welding of uniform quality and reducing welding defects.

In addition, by applying a 20kHz high-frequency inverter power circuit, the welder can be made smaller and lighter, about 1/3 to 1/2 the size of existing products, and the power cost can be maintained at about 60 to 70% of that of existing equipment of the same class.

In addition, it has the advantage of making welding easier for not only experts but also ordinary people by providing a hot-start function to facilitate arc generation when starting welding.

In addition, the anti-stuck function can be implemented to prevent short circuits between the base material and the welding rod that may occur during the welding process, thereby increasing the ease of work.

In addition, the inverter-type welding device proposed by the present invention has the advantage of being able to greatly contribute to the welding industry by improving welding quality, reducing welding costs, and increasing welding productivity by controlling welding output current.

The above description is merely an illustrative description of the technical idea of the present invention, and those skilled in the art will appreciate that various modifications, changes, and substitutions may be made without departing from the essential characteristics of the present invention.

Accordingly, the embodiments disclosed in the present invention and the attached drawings are not intended to limit the technical idea of the present invention but to explain it, and the scope of the technical idea of the present invention is not limited by these embodiments and the attached drawings.

The scope of protection of the present invention should be interpreted by the claims set forth below, and all technical ideas within a scope equivalent thereto should be interpreted as being included in the scope of the rights of the present invention.

Claims (7)

entity; A welding torch connected to the above body and having an electrode provided inside; A welding electrode connected to the above body and connected to a welding material (BM); and It includes a current supply means installed in the above body and supplying current for welding to the electrode of the welding torch and the welding electrode; The above current supply means is, A power input unit connected to commercial AC current, a first rectifier unit that rectifies AC current input from the power input unit into DC current, a smoothing unit that smoothes DC current output from the first rectifier unit, an inverter unit that converts the DC current smoothed by the smoothing unit into variable high-frequency AC current, a transformer unit that transforms AC current output from the inverter unit into low-voltage, high-current suitable for welding, a second rectifier unit that rectifies AC current output through the transformer unit again and converts it into DC voltage, an output terminal that is connected to the electrode of the welding torch and the welding electrode and outputs (+) output and (-) output, and a control unit that controls the overall operation of the current supply means and performs hot start and anti-stuck through a proportional controller. Inverter type proportional control micro welding device. In the first paragraph, The above control unit has a relationship with the output current (i _out ) according to the control signal of the microprocessor, which is derived from the following arithmetic equations (1), (2), and (3). Arithmetic expression (1)

Arithmetic expression (2)

Arithmetic expression (3)

(Here, i _out is the output current, e is the natural constant, u is the control signal, P _w is the PWM duty ratio (%), 0 ≤ P _w ≤ 0.4) Inverter type proportional control micro welding device. In the first paragraph, The above proportional controller If the tracking error (ε) is i _ref - i _out ,

Satisfying the arithmetic expression of , (where, i _ref is the target current, i _out is the output current, u is the control signal, T _i is the integration time [sec], K _p is the proportional gain [A ^-1 ], and K _I is the integral gain [A ^-1 ]) Inverter type proportional control micro welding device. In the third paragraph, The above i _ref is an inverter-type proportional control micro welding device corresponding to the target current of hot start or anti-stuck. In the first paragraph, The above inverter part measures voltage and current, and if the measured current and voltage are different from the set value, operates the proportional controller to follow the set current and set voltage. Inverter type proportional control micro welding device. In the first paragraph, The above control unit satisfies the following arithmetic expression that generates a current that is 0 to 50 [A] higher than the set welding output current depending on the value of the hot start control volume (%) so that arc formation is easy during the hot start function. i _{Hot_start ref} = i _setting + 50×Hot start control volume×

(Here, i _{Hot_start ref} is the target welding current to which the hot start function is applied at the start of welding, i _setting is the set welding current determined by the user, and t _ht is the time from the point in time when the hot start function is activated.) Inverter type proportional control micro welding device. In the first paragraph, When the above control unit measures the voltage between the welding torch (120) and the material to be welded in real time during the anti-stuck function and drops below the reference voltage (Vmin), the welding output voltage satisfies the following arithmetic formula to increase the welding output current by 15 [A] more than the point at which the welding output voltage drops. i _{stuck_ref} = i _setting + 15×

(Here, i _{stuck_ref} is the target welding output current when the anti-stuck function is in effect, and the set welding output current is 140 [A]) Inverter type proportional control micro welding device.

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