CN201231371Y - Novel slant pulse CO2 welding inverter - Google Patents

Abstract

A new type of oblique characteristic pulse _CO2 welding inverter power supply, the _CO2 welding inverter power supply with constant current control current waveform is modified to improve the arc stability performance. The utility model mainly introduces an oblique characteristic type arc length automatic adjustment system into the ordinary _CO2 welding inverter power supply. components such as circuits. The single-chip arc length automatic adjustment module adopts the original oblique characteristic arc length automatic adjustment algorithm, which can calculate the pulse width adjustment amount of the pulse _CO2 welding peak current in real time, so as to automatically adjust the _CO2 welding arc length, so that the utility model has self-adaptive Advantages of pulse _CO2 welding inverter power supply with arc length adjustment function.

Description

A New Slope Characteristic Pulse CO2 Welding Inverter Power Supply

technical field

The utility model relates to an inverter power supply, in particular to a pulse _CO2 gas shielded welding inverter power supply.

Background technique

At present, _CO2 gas shielded welding equipment has widely used inverter DC welding power supply. _CO2 inverter power supply not only has the advantages of small size, light weight and high efficiency, but also develops various pulse or wave-controlled _CO2 welding. The new situation of the machine. Based on the operating frequency of the IGBT inverter power supply up to 20KHz, the control period of the inverter _CO2 welding power supply is only 50us, which has very good dynamic response characteristics, and can control the arcing process and short circuit process of _CO2 welding with a response speed of 0.1ms During the welding process, the current peak value and the base value of the _CO2 welding arc stage are precisely controlled at the set value, which realizes the ideal current waveform control and quantitatively controls the energy of each droplet, thereby greatly Improve the welding performance of the equipment.

However, the pulse _CO2 welding inverter power supply realizes the current waveform control by performing constant current closed-loop control on the current peak value and the base value. That is to say, the pulse _CO2 welding inverter power supply must adopt the constant current control mode to control the current waveform.

As we all know, in constant-speed wire-feeding _CO2 welding equipment, traditionally, the flat characteristic _CO2 welding rectifier power supply is used to solve the problem of automatic adjustment of arc voltage. Otherwise, the arc will not be stable, and the welding process will not be stable either. That is, when the arc length becomes longer or shorter during the _CO2 welding process, the flat characteristic _CO2 power supply will produce a self-regulating effect to reverse the output current, and the melting speed of the welding wire will decrease or increase accordingly, and the welding wire end will be correspondingly The distance between the bottom and the surface of the molten pool becomes smaller or larger, thereby automatically restoring the arc length.

However, when pulsed _CO2 welding equipment adopts constant current control, its external characteristics will become constant current characteristics, which cannot meet the automatic adjustment performance of arc voltage and production needs, so it needs to be improved.

Contents of the invention

The purpose of this utility model is to overcome the shortcomings of the prior art, provide a new type of oblique characteristic pulse _CO2 welding inverter power supply, and transform the _CO2 welding inverter power supply with constant current control current waveform to improve arc stability performance . From the perspective of arc energy control, the utility model studies the method of closed-loop control of _CO2 welding arc voltage by controlling the peak current pulse width _tp of _CO2 welding arc burning process, and establishes the external characteristic slope of pulse _CO2 welding inverter power supply As the criterion, the automatic control model takes the peak current pulse width as the control quantity. On this basis, a new type of oblique characteristic pulse CO ₂ welding power source is proposed. This power supply takes the peak current pulse width of the pulse _CO2 welding inverter power supply as the control quantity, and controls the peak current pulse width through the arc voltage feedback so that the power supply can obtain adjustable slope volt-ampere characteristics, so as to maintain the constant current control peak and base value current characteristics At the same time, it also makes the pulse CO ₂ gas shielded welding inverter power supply have sufficiently strong arc voltage automatic adjustment characteristics.

The technical scheme of the utility model is achieved in that:

A new type of oblique characteristic pulse _CO2 welding inverter power supply is the transformation and performance improvement of the _CO2 welding inverter power supply with constant current control current waveform. It includes the inverter power supply. Its special feature is that it also Including the inclined characteristic type arc length automatic adjustment system, the system takes the peak current pulse width of the pulse CO ₂ welding inverter power supply as the control quantity, and uses the slope of the external characteristic of the power supply as the criterion to carry out negative feedback control on the power supply voltage, so that the pulse CO ₂ The average value of the output current of the welding power source increases linearly as the arc voltage drops, thereby converting the pulse _CO2 welding inverter power source based on the constant current control current waveform into a ramp characteristic pulse _CO2 welding inverter power source; the ramp characteristic arc Length automatic adjustment system, the system is based on single-chip microcomputer and arc length automatic adjustment module, connected with the basic circuit, its circuit includes control panel, AD conversion circuit, wave control parameter conversion circuit, power supply negative feedback circuit, constant current negative feedback Control circuit, PWM control circuit, welding current sensing circuit, welding voltage sensing circuit; real-time detection of welding current I _h value and welding voltage U _h value through the current and voltage sensing circuit, and the welding voltage processed by the sensing circuit The analog quantity U _v is sent to the single-chip CPU through the AD conversion circuit, and then sent to the arc length automatic adjustment module; at the same time, the pulse peak current _Ip , the base value current _Ib and the external characteristic slope K set by the user on the control panel are also sent to the single-chip computer; The arc length automatic adjustment module calculates the adjustment amount Δt _p of the peak current pulse width t _p in real time according to the arc voltage variation ΔU _h and the external characteristic slope K; the wave control parameter conversion circuit switches in real time according to the adjustment amount Δt _p of the peak current pulse width For the current setting value output by the constant current negative feedback circuit, the constant current negative feedback circuit switches the control signal u _k to the PWM control circuit in real time, and then the _CO2 welding inverter main circuit changes the pulse current waveform width, so that the pulse CO _2. The welding inverter power supply automatically adjusts the average value of the welding current to adjust the melting speed of the welding wire and stabilize the arc length.

The basic circuit of the described oblique characteristic type arc length automatic adjustment system is: (A) the arc length automatic adjustment algorithm and signal A/D, D/A conversion are realized by the single-chip microcomputer system; (B) the wave control parameter (current) is realized by the electronic circuit Waveform peak value and base value) conversion, welding current negative feedback control and inverter main circuit pulse width modulation (PWM) control; where:

(1) The welding current wave control parameter conversion circuit is composed of a multi-way switch _u1 and an operational amplifier _u2 ; the input terminals _x0 and _x1 of the multi-way switch _u1 are respectively connected to the D/A module of the single-chip microcomputer system The current peak value I _p , the output terminal of the analog quantity u _p and the output terminal of the current base value I _b analog quantity u _b , the control signal input terminal A is connected to the current peak time t _p switch pulse signal u _t output of the I/O interface circuit of the microcontroller system Terminal, when the u _t pulse signal is high level, the input terminal x of the multiplexer u ₁ . Strobe with the output terminal _x1 , the circuit outputs the set value analog u _p of the welding current waveform peak value, when the u _t pulse signal is low level, the circuit outputs the set value analog u _b of the welding current waveform base value. Operational amplifier U ₂ circuit is used to adjust the current setting value analog signal output from the multi-way switch to U _s value to make it meet the input requirements of the negative feedback control circuit of the welding power supply, and its magnification is adjusted by WR ₁ ;

(2) The negative feedback circuit of the welding power supply is composed of operational amplifiers U ₃ and U ₄ in-phase amplifiers; wherein the operational amplifier U ₃ is used to adjust the analog signal U _i of the welding current sensor to make it consistent with the welding current wave control parameters The output values of the conversion circuit are matched, and its magnification is adjusted by WR _2. The output value U _if is sent to the inverting terminal of _the operational amplifier _{U4 ;} Perform negative feedback processing with welding current analog U _if and output control signal U _k , whose negative feedback intensity is regulated by WR ₃ ;

(3) The pulse width modulation circuit PWM is composed of SG3525 chip. Its input terminal 1 is connected to the output terminal of the welding current negative feedback circuit, and its output terminal generates the switching pulse signal for the inverter main circuit IGBT component.

The single-chip arc length automatic adjustment module of the utility model adopts an original oblique characteristic type arc length automatic adjustment algorithm, which can realize the calculation of the peak current pulse width adjustment amount.

Δtp=-K*T0/Ip*ΔUhp

In the formula: ΔUhp is the change in the average value of pulsed _CO2 welding arc voltage caused by the change of arc length;

T ₀ is the average time of droplet transfer in pulse _CO2 welding;

T _p is the set value of pulse _CO2 welding peak current;

K is the setting value of the external characteristic slope of the slope characteristic pulse _CO2 welding power source. Its function is that when the pulse _CO2 welding arc length changes, the single-chip arc length automatic adjustment module can change the arc voltage variation ΔUhp caused by the arc length change by changing The peak current pulse width is used to generate the corresponding current automatic adjustment value ΔIhp, ΔIhp=T0/Tp*Δtp.

Since Δtp and ΔIhp are negative relative to ΔUhp, their function is a negative feedback function to reduce the change of arc length.

The automatic adjustment function of the single-chip arc length automatic adjustment module:

(1) When the arc length increases, so that ΔUhp increases beyond the reference value Uh0, the pulse width of the peak current pulse width pulse Ut output by the arc length automatic adjustment module is reduced from the set value tp0 to (tp0-Δtp), so that the welding current decrease;

(2) When the arc length decreases to reduce ΔUh, this module increases the Ut pulse width to (tp0-Δtp), and automatically increases the average value of the welding current to restore the arc length.

This system realizes the negative feedback control of the power supply voltage with the peak current pulse width of the pulse _CO2 welding inverter power supply as the control amount and the external characteristic slope of the power supply as the criterion, so that the average output current of the pulse _CO2 welding power supply follows the arc voltage. Decrease and increase linearly, transform the pulse _CO2 welding inverter power supply based on the constant current control current waveform into a slope characteristic pulse _CO2 welding inverter power supply, so that the utility model has the pulse _CO2 welding with the function of self-adaptive adjustment of arc length inverter power supply.

Due to the above-mentioned technical scheme, the utility model has the following advantages and effects:

(1) The oblique characteristic pulse _CO2 welding inverter power supply of this utility model has an adaptive arc length automatic adjustment function. During the welding process, when the arc length changes, the power supply can automatically adjust the welding current average value, so that Change the wire melting speed to restore the arc length.

(2) The arc length automatic adjustment intensity of the oblique characteristic pulse _CO2 welding inverter power supply of the utility model can be quantitatively adjusted by its external characteristic slope, and the pulse _CO2 welding inverter can be increased by reducing the external characteristic slope K value through the control panel The power supply automatically adjusts the arc length intensity.

(3) The oblique characteristic pulse _CO2 welding inverter power supply proposed by the utility model has the function of self-adaptively determining the stable working point of welding. When the welding wire feeding speed must change the welding current peak value or the welding current peak value must change the welding wire feeding speed, the utility model can stabilize the welding average current and average voltage at the new working point, that is, the slope characteristic curve of the power supply and the welding machine, etc. The intersection point of the characteristic curve of fast wire feeding solves the problem of arc voltage self-optimization.

(4) The oblique characteristic pulse _CO2 welding inverter power source proposed by the utility model can not only maintain the constant current control characteristic to accurately control the peak value and base value of the pulse current, but also make the power source have a sufficiently strong arc length automatic adjustment characteristic and arc voltage The self-optimizing function improves the performance of the wave-controlled _CO2 welding inverter power supply.

Description of drawings

Figure 1 is a block diagram of a new type of oblique characteristic pulse _CO2 welding inverter arc length automatic adjustment system

Figure 2 is a schematic diagram of a new type of slope characteristic pulse _CO2 welding inverter power supply control system circuit diagram

Figure 3 is a working principle diagram of the new type of oblique characteristic pulse _CO2 welding inverter power supply to automatically adjust the arc length

Figure 4 is the working principle diagram of the microcomputer arc length automatic adjustment module

Figure 5 is the control flow chart of the single-chip microcomputer for the control system of the inverter power supply control system of the oblique characteristic pulse _CO2 welding

Figure 6 is the measured voltage and current waveform diagram of the slope characteristic pulse _CO2 welding inverter power supply

Detailed ways

Now describe in detail the preferred embodiment of the utility model in conjunction with the accompanying drawings:

A slope characteristic pulse _CO2 welding inverter power supply, its technical characteristics are:

1. Adopt oblique characteristic arc length automatic adjustment system. As shown in Figure 1, the system includes a single-chip microcomputer arc length automatic adjustment module, wave control parameter conversion circuit, power supply negative feedback circuit, constant current negative feedback control circuit, PWM control circuit, welding current sensing circuit, welding voltage sensing circuit, AD conversion circuit and control panel. During the welding process, the system detects the value of welding current I _h and welding voltage U _h in real time through the current and voltage sensing circuit, and sends the analog value U _v of welding voltage processed by the sensing circuit to the single-chip CPU through the AD conversion circuit , and then sent to the arc length automatic adjustment module; at the same time, the pulse peak current I _p , base value current I _b and external characteristic slope K set by the user on the control panel are also sent to the microcontroller; the arc length automatic adjustment module according to the arc voltage variation ΔU _h Calculate the adjustment amount Δt _p of the peak current pulse width t _p in real time with the external characteristic slope K; the wave control parameter conversion circuit switches the current setting value output by the constant current negative feedback circuit in real time according to the adjustment amount Δt _p of the peak current pulse width , so that the constant current negative feedback circuit switches the control signal u _k to the PWM control circuit in real time, and then the _CO2 welding inverter main circuit changes the pulse current waveform width, so that the pulse _CO2 welding inverter power supply automatically adjusts the average value of the welding current to Adjust the melting speed of welding wire to stabilize the arc length.

2. Adopt the inclined characteristic type arc length automatic adjustment system circuit. as shown in picture 2. The basic features of this circuit are: the arc length automatic adjustment algorithm and signal A/D, D/A conversion are realized by the single-chip computer system; the wave control parameter (current waveform peak value and base value) conversion is realized by the electronic circuit, and the welding current negative feedback control and Inverter main circuit pulse width modulation (PWM) control. The specific situation is:

(1) The multi-way switch u ₁ and the operational amplifier u ₂ form a welding current wave control parameter conversion circuit. The input terminals x ₀ and x ₁ of the multi-way switch u ₁ are respectively connected to the current peak value I _p of the D/A module of the single-chip system, the output terminal of the analog quantity _up and the output terminal of the current base value I _b analog quantity u _b , and its control signal input Terminal A is connected to the current peak time t _p switch pulse signal u _t output terminal of the single-chip system I/O interface circuit, when the u _t pulse signal is high level, the input terminal x of the multi-way switch u ₁ . Strobe with the output terminal _x1 , the circuit outputs the set value analog u _p of the welding current waveform peak value, when the u _t pulse signal is low level, the circuit outputs the set value analog u _b of the welding current waveform base value. Operational amplifier U ₂ circuit is used to adjust the current setting value analog signal output from the multi-way switch to U _s value to make it meet the input requirements of the negative feedback control circuit of the welding power supply, and its magnification is adjusted by WR ₁ ;

(2) Operational amplifier U ₃ and U ₄ in-phase amplifying electrical appliances form a welding power supply negative feedback circuit. The operational amplifier U ₃ is used to adjust the analog signal U _i of the welding current sensor to match the output value of the welding current wave control parameter conversion circuit, its magnification is adjusted by WR ₂ , and its output value U _if is sent to the operational amplifier The inverting terminal of U ₄ ; the non-inverting terminal of the operational amplifier U ₄ enters the analog quantity U _s of the welding current waveform parameter, so that it can perform negative feedback processing with the analog quantity U _if of the welding current and output a control signal U _k , and its negative feedback intensity is determined by WR ₃ regulation;

(3) The pulse width modulation circuit PWM is composed of SG3525 chip. Its input terminal 1 is connected to the output terminal of the welding current negative feedback circuit, and its output terminal generates the switching pulse signal for the inverter main circuit IGBT component.

3. The single-chip microcomputer arc length automatic adjustment module adopts the original oblique characteristic arc length automatic adjustment algorithm, which can realize the peak current pulse width adjustment amount

Δtp=-K*T0/Ip*ΔUhp

In the formula: ΔUhp is the change in the average value of pulsed _CO2 welding arc voltage caused by the change of arc length;

T ₀ is the average time of droplet transfer in pulse _CO2 welding;

T _p is the set value of pulse _CO2 welding peak current;

K is the setting value of the external characteristic slope of the slope characteristic pulse _CO2 welding power source. Its function is that when the pulse _CO2 welding arc length changes, the single-chip arc length automatic adjustment module can change the arc voltage variation ΔUhp caused by the arc length change by changing The peak current pulse width is used to generate the corresponding current automatic adjustment value ΔIhp, ΔIhp=T0/Tp*Δtp Since Δtp and ΔIhp are negative relative to ΔUhp, its function is to reduce the arc length change. Negative feedback function.

4. The single-chip microcomputer arc length automatic adjustment module converts the pulse CO ₂ welding inverter power supply based on the constant current control current waveform into a slope characteristic pulse CO ₂ welding inverter power supply. As shown in Figure 3;

(1) When the arc length increases, so that ΔUhp increases beyond the reference value Uh0, the pulse width of the peak current pulse width pulse Ut output by the arc length automatic adjustment module is reduced from the set value tp0 to (tp0-Δtp), so that the welding current Decrease, so that the pulse width of the peak current output by the pulse _CO2 welding power source decreases linearly with the increase of the arc voltage, and the average value of the output current of the power source also decreases linearly with the increase of the arc voltage;

(2) When the arc length decreases and ΔUh decreases, this module increases the Ut pulse width to (tp0-Δtp), automatically increases the average value of the welding current, and makes the peak current pulse width output by the pulse _CO2 welding power supply follow the arc When the voltage decreases and increases linearly, the average value of the output current of the power supply also increases linearly with the decrease of the arc voltage. Therefore, the single-chip microcomputer arc length automatic adjustment module of the utility model converts the pulse _CO2 welding inverter power supply based on the constant current control current waveform It is an inverter power supply for slope characteristic pulse CO ₂ welding.

5. The mechanism of the inclined characteristic pulse CO ₂ welding inverter power supply to automatically adjust the arc length is: take the peak current pulse width as the control amount, and use the slope of the external characteristic of the power supply as the criterion to carry out negative feedback control on the power supply voltage.

As shown in Figure 4 _, the intersection point O of the oblique outer characteristic and the _constant -speed wire-feeding characteristic curve in the figure is the stable operating point. It becomes the O' point, and its current value is reduced by ΔI _h compared with the stable operating point, that is, the power supply automatically generates an arc current adjustment value ΔI _h to reduce the melting speed of the welding wire, making it lower than the feeding speed of the welding wire, and the end of the welding wire moves toward the molten pool Moving, the welding working point gradually recovers from the fluctuation point O' to the stable working point O, keeping the arc length stable.

6. The arc length of the automatic adjustment intensity of the utility model can be adjusted by the external characteristic slope value K of the pulse _CO2 welding inverter power supply.

As the slope K value increases, the external characteristic curve of the power source tends to be gentle, that is, the output current adjustment amount of the power source caused by the change of the unit arc voltage becomes larger, and the arc length automatic adjustment function of the slope characteristic pulse _CO2 welding power source becomes stronger.

7. Double closed-loop negative feedback control of arc current and arc voltage is adopted. The utility model not only keeps the power source through the arc length automatic adjustment system, but also maintains the characteristics that the pulse _CO2 welding machine can accurately control the current waveform according to the set value, including controlling the current peak value and base value during arc burning and the current waveform of short-circuit transition; At the same time, the power supply can obtain the slope-outside characteristic with adjustable slope, so as to have the arc length automatic adjustment function equivalent to the flat characteristic power supply.

8. The utility model uses a single-chip microcomputer control program to perform real-time closed-loop control on the current waveforms of the arcing process and the short-circuit process.

As shown in Figure 5, the single-chip microcomputer system controls the peak time of the arcing current during the welding process and the set value of the short-circuit current waveform during the short-circuit transition process in real time. In the CO ₂ welding arcing stage, the single-chip microcomputer performs closed-loop control on the welding voltage and current, and determines the adjustment value of the peak current pulse width t _p according to the sampling value of the welding voltage U _h , that is, controls the arcing current by adjusting the value of t _p in real time The peak waveform enables the power supply to have the function of automatically adjusting the arc length. In the short-circuit stage of CO ₂ welding, the single-chip microcomputer is used to output the short-circuit current setting waveform to the constant current negative feedback control circuit to precisely control the short-circuit current waveform, so that it changes according to the setting value of the single-chip microcomputer.

Fig. 6 is the measured result of an example of the utility model. In this example, the external characteristic slope of the pulse CO ₂ welding inverter power supply is 4A/V, the peak current setting value of pulse CO ₂ welding is 400A, and the base value current setting value is 50A. It can be seen from the figure that the pulse _CO2 welding process is stable, and the peak value and base value of the slope current of the external characteristic of the pulse power supply are consistent with the set value.

Claims (2)

1, a kind of novel oblique characteristic type pulse CO ₂The weldering inverter is the CO to constant current control current waveform ₂The transformation and the performance of weldering inverter improve, and it comprises inverter, it is characterized in that: it also comprises oblique characteristic type arc length automatic regulating system, and this system is with pulse CO ₂Weldering inverter peak point current pulsewidth is a controlled quentity controlled variable, is criterion with the generator characteristic slope, and supply voltage is carried out negative-feedback control, makes pulse CO ₂Weldering electric power outputting current mean value descends and linear increasing with arc voltage, thereby will control the pulse CO of current waveform based on constant current ₂The weldering inverter changes oblique characteristic type pulse CO into ₂The weldering inverter; Described oblique characteristic type arc length automatic regulating system, this system is a core with single-chip microcomputer and the automatic adjustment module of arc length, be formed by connecting with basic circuit, its circuit comprises control panel, A/D convertor circuit, ripple control parameter change-over circuit, power-feedback circuit, constant current negative feedback control circuit, pwm control circuit, welding current sensing circuit, weldingvoltage sensing circuit; Detect welding current I in real time by electric current and voltage sensing circuit _hValue and weldingvoltage U _hThe value, and with sensing circuit handle weldingvoltage analog quantity U _vSend into singlechip CPU through A/D convertor circuit, send into the automatic adjustment module of arc length again; The user is at the pulse peak current I of control panel setting simultaneously _p, background current I _bAlso send into single-chip microcomputer with the external characteristics slope K; The automatic adjustment module of arc length is according to arc voltage variation Δ U _hCalculate peak point current pulsewidth t in real time with the external characteristics slope K _pRegulated quantity Δ t _pRipple control parameter change-over circuit is then according to the regulated quantity Δ t of peak point current pulsewidth _pSwitch current setting value in real time, make the switching in real time of constant current negative-feedback circuit the control signal u of pwm control circuit to the output of constant current negative-feedback circuit _k, make CO then ₂The weldering inverter main circuit changes the pulse current waveform width, thereby makes pulse CO ₂The weldering inverter is regulated welding current mean value automatically and is regulated welding wire melting rate, stable arc length.

2, novel oblique characteristic type pulse CO according to claim 1 ₂The weldering inverter, it is characterized in that: described oblique characteristic type arc length automatic regulating system basic circuit is: (A) realize that by SCM system arc length is regulated algorithm automatically and signal A/D, D/A change; (B) realize ripple control parameter (current waveform peak value and base value) conversion by electronic circuit, welding current negative-feedback control and inverter main circuit pulsewidth modulation (PWM) control; Wherein: (1) described welding current ripple control parameter change-over circuit is by variable connector u ₁With operational amplifier u ₂Form; Variable connector u ₁Input x ₀, x ₁Meet the current peak I of SCM system D/A module respectively _p, analog quantity u _pOutput and electric current base value I _bAnalog quantity u _bOutput, its control signal input A meets the current peak time t of SCM system I/O interface circuit _pSwitching pulse signal u _tOutput, u _tWhen pulse signal is high level, variable connector u ₁Input x.With output x ₁Gating, the setting value analog quantity u of circuit output welding current waveform peak value _p, u _tWhen pulse signal is low level, the setting value analog quantity u of circuit output welding current waveform base value _bOperational amplifier U ₂Circuit is in order to adjust current setting value analog signal from variable connector output to U _sValue makes it symbol source of welding current negative feedback control circuit input requirement, and its multiplication factor is by WR ₁Regulate;

(2) described source of welding current negative-feedback circuit is by operational amplifier U ₃With U ₄The homophase amplification appliance is formed; Operational amplifier U wherein ₃Analog signals U in order to conditioning welding current sensing _iMake it to be complementary with welding current ripple control parameter change-over circuit output valve, its multiplication factor is by WR ₂Regulate its output valve U _IfSend into operational amplifier U ₄End of oppisite phase; Operational amplifier U ₄In-phase end go into welding current waveform parameter simulation amount U _s, make it and welding current analog quantity U _IfCarry out negative-feedback process and export control signal U _k, its negative-feedback intensity is by WR ₃Regulate; (3) pulse-width modulation circuit PWM adopts the SG3525 chip to form, and its input 1 connects welding current negative-feedback circuit output, and its output produces the switching pulse signal to converter main circuit IGBT element.

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