CN110239104B - Method for automatically compensating output voltage of direct current inversion electric fusion welding machine - Google Patents
Method for automatically compensating output voltage of direct current inversion electric fusion welding machine Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C65/00—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
- B29C65/02—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure
- B29C65/18—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated tools
- B29C65/22—Heated wire resistive ribbon, resistive band or resistive strip
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C66/00—General aspects of processes or apparatus for joining preformed parts
- B29C66/50—General aspects of joining tubular articles; General aspects of joining long products, i.e. bars or profiled elements; General aspects of joining single elements to tubular articles, hollow articles or bars; General aspects of joining several hollow-preforms to form hollow or tubular articles
- B29C66/51—Joining tubular articles, profiled elements or bars; Joining single elements to tubular articles, hollow articles or bars; Joining several hollow-preforms to form hollow or tubular articles
- B29C66/52—Joining tubular articles, bars or profiled elements
- B29C66/522—Joining tubular articles
- B29C66/5221—Joining tubular articles for forming coaxial connections, i.e. the tubular articles to be joined forming a zero angle relative to each other
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C66/00—General aspects of processes or apparatus for joining preformed parts
- B29C66/80—General aspects of machine operations or constructions and parts thereof
- B29C66/87—Auxiliary operations or devices
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C66/00—General aspects of processes or apparatus for joining preformed parts
- B29C66/90—Measuring or controlling the joining process
- B29C66/95—Measuring or controlling the joining process by measuring or controlling specific variables not covered by groups B29C66/91 - B29C66/94
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C66/00—General aspects of processes or apparatus for joining preformed parts
- B29C66/90—Measuring or controlling the joining process
- B29C66/96—Measuring or controlling the joining process characterised by the method for implementing the controlling of the joining process
- B29C66/962—Measuring or controlling the joining process characterised by the method for implementing the controlling of the joining process using proportional controllers, e.g. PID controllers [proportional–integral–derivative controllers]
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Abstract
The invention relates to a plastic pipeline electric fusion welding technology, and aims to provide a method for automatically compensating output voltage of a direct current inversion electric fusion welding machine. The method comprises the following steps: according to the resistance value R and the inductance value L of the electric melting pipe fitting and the full-wave effective voltage U of the alternating current electric melting welding machine0Welding voltage U for electric melting pipe fittingsACalculating a power factor lambda when the alternating current welding machine is used for setting; or, calculating the power factor lambda by adopting a fitting formula; and then compensating the output voltage of the direct current inverter welding machine to ensure that the actual direct current welding process is equal to the alternating current welding power on the electric melting pipe fittings when the welding process parameters are determined. The method can effectively eliminate the influence of the power factor on the actual heat obtained by the electric melting pipe fitting, so that the welding process meets the optimal process requirement, and the occurrence of the over-welding defect is effectively prevented. The control method can be conveniently added into the existing digital welding machine, so that the novel electric fusion welding machine with the functions of automatically compensating output voltage and preventing over-welding is formed.
Description
Technical Field
The invention relates to an electric fusion welding technology for plastic pipelines, which comprises an electric fusion welding technology for reinforced plastic composite pipes such as high-density polyethylene pipes, steel wires/steel belts and the like, and reinforced plastic composite pipes such as glass fibers/carbon fibers, aramid fibers and the like.
Background
Compared with metal pipelines, the plastic pipeline and the composite pipeline have the advantages of corrosion resistance, good flexibility, light weight, long service life, designable performance and the like, and are widely applied to the fields of building water supply and drainage, ore pulp conveying, gas conveying, oil field gathering and conveying, nuclear power station cooling water conveying and the like. Electrofusion joining is the most common way of joining plastic and composite pipes.
Electric fusion welding is a physical fusion process of materials: the end of a plastic pipe or a composite pipe to be connected is inserted into an electric melting sleeve embedded with a resistance wire, and the outer surface of the pipe is in close contact with the inner surface of the sleeve. And connecting the electric melting sleeve to a power supply with fixed voltage to electrify the embedded resistance wire in the electric melting pipe fitting to generate heat. The heat is gradually transferred to the polyethylene material in the pipe and the sleeve, so that the outer wall surface of the pipe and the inner wall surface of the pipe fitting are gradually melted into a whole. After the electric melting welding is finished, the joint is slowly cooled, an original welding interface disappears, and the electric melting joint with certain strength is formed.
At present, electric welding machines in domestic market can be divided into an inverter type direct current welding machine and a phase control type alternating current welding machine according to control modes. The phase-control AC electric fusion welding machine (hereinafter referred to as AC welding machine) mainly adopts the phase-shift control principle of silicon controlled rectifier and utilizes thyristor to regulate voltage. The scheme is adopted by imported electric melting welding machines such as RITMO in Italy and plastic dragon in France and many domestic electric melting welding machines. The advantages are that: the circuit is simple and easy to realize. The disadvantages are that: (1) large volume, heavy mass: because the commercial power frequency is 50HZ, so must back a bulky annular power frequency transformer of volume, make the whole weight increase of electric fusion welding machine, the current domestic phase control type exchanges electric fusion welding machine weight and generally is more than 20KG, imported not being less than 17KG yet, leads to the field construction transport inconvenient. (2) Low efficiency: the transformer has large loss and reduces the working efficiency of the whole machine. (3) There is a higher harmonic interference to the grid.
For an inverter type electric fusion welding machine (hereinafter referred to as a direct current welding machine), high-frequency switch control of turn-off power devices (IGBT, IPM and GTR) is utilized. The power frequency voltage is subjected to full-wave rectification, high-frequency inversion, transformation by a high-frequency transformer, rectification again and filtering, and finally the required voltage is obtained. The scheme has the greatest advantage that the high-frequency transformer is adopted to replace the traditional power frequency transformer, the iron core material of the power frequency transformer is silicon steel sheets, and the iron core material of the high-frequency transformer is ferrite. The ferrite is a composite oxide sintered body, the main components of the ferrite are Zn, Mn and the like, the magnetic conductivity is high, when a certain number of turns of the coil is adopted, higher magnetic induction intensity can be achieved through small exciting current, and the coil can bear higher applied voltage, so that the volume of the magnetic core can be reduced under the requirement of outputting certain power, the weight and the volume of the whole welding machine are greatly reduced, and the field construction and carrying are very facilitated. The coercive force of the magnetic core is low, and the hysteresis loop area is small, so that the iron loss is also small. And when the iron core has higher resistivity, the generated eddy current is small, and the iron loss is also small. Therefore, the high-frequency transformer has high working efficiency which is generally over 90 percent, small temperature influence, low price and controllable output voltage error of +/-0.2 v. The combination with the single chip microcomputer is good in controllability, and the extended functions can be flexibly controlled according to the requirements of users.
In recent 10 years, inverter type direct current fusion welding machines based on different types of single-chip microcomputers and embedded systems are proposed in China including Zhejiang university, southeast university, Tianjin university, Guangdong industry university and the like, and a plurality of manufacturers also produce light inverter type direct current fusion welding machine products. However, in the field use process, the problems of material overflow and the like easily occur to the electric melting pipe fittings welded by the inverter type direct current welding machine, so that the electric melting joint is over-welded. Therefore, the phase-control type alternating current welding machine is still commonly used in the fields of gas pipelines and the like with poor industrial acceptance of the inverter type welding machine and high requirements on safety.
Through intensive research, the applicant finds that the phenomenon is mainly caused by the joint influence of a process determination method in the electric melting pipe fitting industry and the voltage output characteristic of electric melting welding.
The electric melting pipe fitting industry adopts different wiring processes for electric melting pipe fittings of different specifications, then adopts a phase control type alternating current welding machine with 39.5V standard voltage to weld, and determines the optimal electric melting welding time suitable for the specification by testing the welding interface strength of electric melting joints of different welding time. For example, the electrical resistance of the electrical fused pipe fitting with the DN90 straight-through is 1.05 ohm, and the optimal welding time is determined in the development process by welding the electrical fused pipe fitting with the phase control type ac welding machine of 39.5V for 80 seconds, 90 seconds, 100 seconds, 110 seconds, 120 seconds and the like, respectively, and then performing destructive testing on the welded joint, wherein the welding time of the joint with the best strength is defined as the standard welding time. In engineering applications, unless otherwise specified, welding with an ac welder is recommended by default, but welding with a dc welder is not excluded.
On the other hand, the phase-control type ac welder outputs the chopped ac power, and the inverter type dc welder outputs the flat dc power. Because the resistance wire in the electric melting pipe fitting is wound on the inner wall of the pipe fitting in a spiral line mode, the resistance wire has certain inductance besides resistance. Particularly, the alternating current is subjected to high-frequency harmonic wave after chopping, so that the inductive reactance of the resistor is greatly increased. Therefore, when the electric melting pipe fittings are welded for a certain time, the electric melting pipe fittings actually act on the resistance R and the inductance L of the electric melting pipe fittings by using the alternating current welding machine, although the output voltage hasEffective value is UMaking a business39.5V, but the actual active power P is due to the phase difference between the current and the voltageIs provided withLess than apparent power PVisionI.e. if the equivalent is the DC voltage output, the equivalent voltage UStraight barLess than UMaking a business(39.5V)。
Therefore, the equivalent direct current welding voltage of the electric melting pipe fitting determined by the welding time of the phase control type alternating current welding machine is lower than 39.5V. Therefore, when welding is performed by an inverter type dc welding machine, the output dc welding voltage is 39.5V, which actually exceeds the welding voltage at the time of setting the time for welding the electrofusion pipe, and therefore, the welding is likely to be over-welded or even sprayed.
Therefore, the problem to be solved by the invention is how to adopt a direct current inverter welding machine to weld the electric melting pipe fittings, even if the welding parameters of the electric melting pipe fittings are set by an alternating current welding machine, the effect of alternating current welding of the electric melting pipe fittings can be simulated, and the phenomenon of over-welding can not occur.
Disclosure of Invention
The invention aims to solve the technical problem of overcoming the defects of the prior art and provides a method for automatically compensating the output voltage of a direct current inversion electric melting welding machine. If the welding process parameters of the electric melting pipe fitting are determined based on the alternating current welding, a certain amount of output voltage can be automatically compensated, so that the power of the direct current welding is equal to the active power of the alternating current welding, and the consistency of the direct current welding process and the alternating current welding process is ensured.
In order to solve the problems, the technical scheme adopted by the invention is to provide a method for automatically compensating the output voltage of a direct current inversion electric melting welding machine, which comprises the following steps:
(1) obtaining power factor lambda of AC electric fusion welding machine for setting welding process parameters
According to the resistance value R and the inductance value L of the electric melting pipe fitting and the full-wave effective voltage U of the alternating current electric melting welding machine0Welding voltage U for electric melting pipe fittingsACalculating a power factor lambda when the alternating current welding machine is used for setting; wherein the full waveform effective voltage U of the AC electric fusion welding machine0Refers to Alternating Current (AC)220V power input by an alternating current electric fusion welding machineThe effective value of full waveform voltage before chopping after voltage reduction by a transformer;
(1.1) calculating the effective value of the output voltage
According to the instantaneous value of the chopping voltage output by the alternating current welding machine:
and an effective voltage calculation formula, wherein the effective value of the output voltage is obtained by calculation:
each symbol in the above formula:
u (t) is the output voltage instantaneous value, V; u shape0Fully waveform effective voltage V after voltage reduction for the welding machine; k is any natural number and is dimensionless; theta is the chopping angle, rad, of the output chopping voltage; ω 2 pi f, rad/s, where f is the alternating current frequency (mains is 50 Hz); u shapemIs the effective value of the output voltage, V; t is time, s; pi is the circumference ratio and is dimensionless;
(1.2) converting the voltage into a complex exponential form
Performing a complex exponential form transformation of the fourier transform on the output voltage:
wherein,
all the Fourier transform coefficients corresponding to k omega, and j is an imaginary number unit; tan (r) is-1Is an inverse function of tan, namely arctan, and has a value range (-pi, pi);
a0＝0
in the formula: a is-1，b-1，a0，b0，ak，bkAll are Fourier transform coefficients, and k is a natural number;
(1.3) converting the complex impedance into a complex exponential functional form
Wherein,
all the Fourier transform coefficients corresponding to k omega;
each symbol in the above formula:
z is the complex impedance of the electric melting pipe fitting; r is the resistance value of the electric melting pipe fitting, omega; l is the inductance value of the electric melting pipe fitting, H;
(1.4) calculating the effective value of the current
The complex exponential functional form of the current is:
according to a calculation formula of the current effective value, the current effective value is calculated as follows:
each symbol in the above formula:
i (t) is the instantaneous value of the output current, A; i.e. imIs the effective value of the output current, a; i (t)ReA real part representing a complex form of the current; t is the period of alternating current, s (the commercial power is 0.02 s);
(1.5) calculating apparent Power and active Power
The apparent power is:
the active power is:
each symbol in the above formula: SP is the apparent power, W; RP is active power, W; u (t)ReA real part representing a complex form of the voltage;
(1.6) calculating the Power factor
The power factor is the ratio of active power to apparent power of the welder:
in the above formula: λ is a power factor;
(2) compensating output voltage of DC inverter welding machine
In order to make the actual direct current welding process equal to the alternating current welding power on the electric melting pipe fitting when determining the welding process parameters, the output voltage of the direct current inversion electric melting welding machine during welding is compensated:
the formula for ensuring equal welding power of the electric melting pipe fittings in the two processes is as follows:
the voltage compensation is determined by the following equation:
in the formula, P is the welding power of the electric melting pipe fitting in the welding process; u shapeDThe voltage compensation is carried out on the actual output voltage V of the direct current inversion electric fusion welding machine after voltage compensation; u shapeAAn alternating current welding voltage, V, specified for the electrofusion pipe fitting welding process; λ is the power factor obtained from the calculation of step (1).
The invention also provides a method for automatically compensating the output voltage of the direct current inversion electric melting welding machine, which comprises the following steps:
(1) calculating the power factor lambda of the alternating current electric fusion welding machine for setting the welding process parameters by adopting a fitting formula:
λ＝[A1·ke 2+A2·ke+A3]·[B1·ke 3+B2·ke 2+B3·ke+B4]
in the formula A1、A2、A3、B1、B2、B3、B4Are all coefficients; u. ofeThe pressure regulating coefficient in the welding process; k is a radical ofeIs the inductance-resistance ratio; the expression of each coefficient is as follows:
in the formula, R is the resistance value of the electric melting pipe fitting, omega; l is the inductance value of the electric melting pipe fitting, H; u shape0The full waveform effective voltage of the alternating current welding machine; u shapeAIs the welding voltage of the electric melting pipe fitting;
(2) compensating output voltage of DC inverter welding machine
In order to make the actual direct current welding process equal to the alternating current welding power on the electric melting pipe fitting when determining the welding process parameters, the output voltage of the direct current inversion electric melting welding machine during welding is compensated:
the formula for ensuring equal welding power of the electric melting pipe fittings in the two processes is as follows:
the voltage compensation is determined by the following equation:
in the formula, P is the welding power of the electric melting pipe fitting in the welding process; u shapeDThe voltage compensation is carried out on the actual output voltage V of the direct current inversion electric fusion welding machine after voltage compensation; u shapeAAn alternating current welding voltage, V, specified for the electrofusion pipe fitting welding process; λ is the power factor obtained from the calculation of step (1).
In the invention, before the operation of the step (1) is executed, whether output voltage compensation is needed or not is confirmed according to the welding process parameter type of the electric melting pipe fitting; if the electric melting pipe fittings are specified to be welded by direct current voltage (usually DC 39.5V), no additional output voltage compensation is needed; if the electrofusion pipe is welded using an alternating voltage (usually AC 39.5V), the output voltage needs to be compensated.
The invention further provides a direct current inversion electric fusion welding machine with an output voltage automatic compensation function, which comprises a processor for loading a control function module; an output voltage automatic compensation module for realizing the method is loaded in the processor; the electric melting welding machine also comprises a resistance measuring circuit connected to the processor through a lead and used for measuring the resistance value of the electric melting pipe fitting; the operation panel of the electric fusion welding machine is provided with a selection key for compensating the output voltage, a selection key for measuring the resistance R of the electric fusion pipe fitting before welding and a selection key for inputting the full-wave effective voltage U of the alternating current electric fusion welding machine0And an input interface of the inductance value L of the electric melting pipe fitting.
Compared with the prior art, the invention has the beneficial effects that:
1. by the method, the electric melting pipe fitting using the alternating current electric melting welder for setting the welding process parameters is compensated by the output voltage of the direct current inversion electric melting welder when the direct current inversion electric melting welder is used for actual welding, so that the influence of a power factor on actually obtained heat of the electric melting pipe fitting can be effectively eliminated, the welding process meets the optimal process requirement, and the occurrence of the over-welding defect is effectively prevented.
2. The control method of the invention can be conveniently added into the existing digital welding machine, so that the welding machine becomes a novel electric fusion welding machine with the functions of automatically compensating output voltage and preventing over-welding.
Drawings
FIG. 1 is a welding flow chart of the DC welding machine with voltage automatic compensation function according to the present invention.
Detailed Description
The invention relates to an automatic welding machine technology of an electric melting pipe fitting, and belongs to an application of a computer technology in the technical field of welding. In the implementation process of the invention, the application of a plurality of software functional modules is involved. The applicant believes that it is fully possible for one skilled in the art to utilize the software programming skills in his or her own practice to implement the invention, as well as to properly understand the principles and objectives of the invention, in conjunction with the prior art, after a perusal of this application. The aforementioned software functional modules include but are not limited to: the output voltage automatic compensation module, the control function module and the like belong to the scope mentioned in the application document of the invention, and the applicant does not enumerate one by one.
In the invention, before the direct current inversion electric melting welder is used for welding the electric melting pipe fittings, whether output voltage compensation is needed or not is judged. If the electric melting pipe fittings are specified to be welded by direct current voltage (usually DC 39.5V), no additional output voltage compensation is needed; if the electrofusion pipe is welded using an alternating voltage (usually AC 39.5V), the output voltage needs to be compensated.
For an electric melting pipe fitting of an alternating current welding process, a resistance value R and an inductance value L of the electric melting pipe fitting are measured before the electric melting pipe fitting is welded by a direct current inverter welding machine. According to the resistance value R and the inductance value L of the electric melting pipe fitting, the full wave of the alternating current electric melting welding machineEffective voltage U0Welding voltage U of electric melting pipe fittingAThe four parameters can be calculated to obtain the power factor lambda in the process of obtaining welding process parameters by testing the alternating current electric melting welder.
The power factor is calculated according to the following formula:
λ＝[A1·ke 2+A2·ke+A3]·[B1·ke 3+B2·ke 2+B3·ke+B4]
in the formula A1、A2、A3、B1、B2、B3、B4Are all coefficients; u. ofeThe pressure regulating coefficient in the welding process; k is a radical ofeIs the inductance-resistance ratio; the expression of each coefficient is as follows:
in order to make the welding power on the electric melting pipe fitting in the actual direct current welding process equal to the alternating current welding power on the electric melting pipe fitting when the welding process parameters are determined, the output voltage of the direct current inversion electric melting welding machine during welding is compensated. The equation for ensuring equal welding power of the electric melting pipe fittings in the two processes is as follows:
in the formula, P is the welding power of the electric melting pipe fitting in the welding process; u shapeDThe voltage compensation is carried out on the actual output voltage V of the direct current inversion electric fusion welding machine after voltage compensation; u shapeAThe welding voltage V is obtained by testing the electric melting pipe fitting by an alternating current welding machine; and lambda is the power factor of the electrofusion pipe fitting in the process of setting welding technological parameters by an alternating current fusion welding machine.
The voltage compensation is then determined by the following equation:
since the power factor λ is always less than 1, it can be seen that if the ac welding voltage U used for the welding process is setA39.5V, the DC welding voltage UDNecessarily less than 39.5V. Therefore, the output voltage of the DC inversion electrofusion welding machine should be in accordance with
And compensation is carried out, so that the overwelding defect caused by overlarge heat obtained by the electric melting pipe fitting is prevented.
The specific implementation steps for realizing the automatic compensation function of the output voltage of the direct current inverter welding machine are as follows:
(1) judging whether output voltage compensation is needed
If the electric melting pipe fittings are specified to be welded by direct current voltage (such as DC 39.5V), additional output voltage compensation is not needed;
if the electric melting pipe fitting is welded by adopting alternating voltage (such as AC 39.5V), the output voltage needs to be compensated, a newly-added voltage compensation key is pressed on an operation panel of the welding machine, a control system of the welding machine is converted into a voltage compensation program, and then the following steps are carried out to realize welding;
(2) parameter input before welding
Before the electric melting welder is connected with the electric melting pipe fitting, an inductance value L of the electric melting pipe fitting to be welded is obtained by using a universal meter for measurement.
Then be connected electric fusion welding machine and electric smelting pipe fitting, before the welding begins, carry out parameter input operation:
inputting effective voltage U of full waveform of AC electric melting welder used for determining technological parameters of electric melting pipe fittings on operation panel of welder0Welding voltage U of electric melting pipe fittingAAnd the inductance value L of the electric melting pipe fitting.
(3) Resistance measurement before welding
After the electric melting welding machine is connected with the electric melting pipe fitting, a resistance measuring key additionally arranged on the operation panel is pressed, the welding machine outputs 3-5V voltage, the voltage and the current value on a welding line are measured, and the initial resistance value of the electric melting pipe fitting can be obtained according to the following formula
In the formula, RfThe initial resistance value of the electrofused pipe fitting, Ω; u shape0Measuring the voltage value V at two ends of the welding wire; i is0Is the current value on the weld line, A;
(4) control phase in welding process
The welding machine can obtain the resistance value R and the inductance value L of the electric melting pipe fitting and the full-wave effective voltage U of the alternating current electric melting welding machine according to the parameter input and the resistance measurement stage0Welding voltage U of electric melting pipe fittingAThe four parameters can be calculated to obtain the power factor lambda if the AC electric fusion welding machine is used for welding, and then the power factor lambda is calculated according to the power factor lambda
And compensating the output voltage of the direct current inverter welding machine to realize the automatic compensation function of the output voltage of the direct current inverter welding machine.
In order to realize the functions, the existing measurement circuit and operation panel of the electric fusion welding machine need to be improved:
(1) a selection key for compensating the output voltage is added on the operation panel;
(2) a measuring circuit for measuring the resistance R of the electric melting pipe fitting before welding is added into the measuring circuit;
(3) a resistance measuring key is added on the operation panel;
(4) increasing effective full-wave voltage U of AC electric welding machine on operation panel0And an input interface of an inductance value L of the electric melting pipe fitting.
Specific example 1:
in the example, a direct current inversion electric melting welder is used for welding the DN200 straight-through medium-cost electric melting pipe fitting, and the welding process parameter of the electric melting pipe fitting is formed by full-wave effective voltage U after transformation0The welding voltage was determined to be 39.5V for an ac electrofusion welder of 92V. The whole welding process is as follows:
(1) judging whether output voltage compensation is needed
And checking the welding process parameter type of the electric melting pipe fitting of a certain brand directly connected by DN200, wherein the welding process parameter type is AC voltage welding. Pressing a newly added voltage compensation key on an operation panel of the welding machine, and converting a control system of the welding machine into a voltage compensation program;
(2) parameter input before welding
Before the electric melting welder is connected with the electric melting pipe fitting, an inductance value L of the electric melting pipe fitting to be welded is 310.6uH measured by using a multimeter. Then be connected electric fusion welding machine and electric smelting pipe fitting, before the welding begins, carry out parameter input operation:
inputting effective voltage U of full waveform of AC electric melting welder used for determining technological parameters of electric melting pipe fittings on operation panel of welder092V welding voltage U of electric melting pipe fittingA39.5V and the inductance L of the electric melting pipe is 310.6 uH.
(3) Resistance measurement before welding
After the electric melting welding machine is connected with the electric melting pipe fitting, a resistance measuring key additionally arranged on the operation panel is pressed, the welding machine outputs 3-5V voltage, the voltage and the current value on a welding line are measured, and the initial resistance value of the electric melting pipe fitting can be obtained according to the following formula
In the formula, RfThe initial resistance value of the electrofused pipe fitting, Ω; u shape0Measuring the voltage value V at two ends of the welding wire; i is0Is the current value on the weld line, A;
(4) control phase in welding process
The welding machine can obtain the resistance value R of the electric melting pipe fitting which is 1.15 omega, the inductance value L of the electric melting pipe fitting which is 310.6uH and the full-waveform effective voltage U of the alternating current welding machine according to the parameter input and the resistance measurement stage092V welding voltage U of electric melting pipe fittingAThe power factor lambda obtained by substituting four parameters such as 39.5V into the power factor fitting calculation formula can be calculated according to the power factor lambda 0.9487 obtained by welding with the ac electric fusion welding machine
The output voltage of the DC inverter welding machine is compensated, the automatic compensation function of the output voltage of the DC inverter welding machine is realized, and the welding voltage U output by the actual DC inverter electric melting welding machineD＝38.5V。
Specific example 2:
in the present example, the DC inversion electrofusion welding machine is used for directly connecting the DN450 direct-connected medium-cost power supplyWelding the fused pipe fitting, wherein the welding technological parameters of the fused pipe fitting are the full-wave-shaped effective voltage U after transformation0The welding voltage was determined to be 60V for a 92V ac electrofusion welder. The whole welding process is as follows:
(1) judging whether output voltage compensation is needed
And checking the welding process parameter type of the DN450 straight-through electric melting pipe fittings of a certain brand, wherein the welding process parameter type is AC voltage welding. Pressing a newly added voltage compensation key on an operation panel of the welding machine, and converting a control system of the welding machine into a voltage compensation program;
(2) parameter input before welding
Before the electric melting welder is connected with the electric melting pipe fitting, an inductance value L of the electric melting pipe fitting to be welded is 500.8uH measured by using a multimeter. Then be connected electric fusion welding machine and electric smelting pipe fitting, before the welding begins, carry out parameter input operation:
inputting effective voltage U of full waveform of AC electric melting welder used for determining technological parameters of electric melting pipe fittings on operation panel of welder092V welding voltage U of electric melting pipe fittingA60V and the inductance L of the electric melting pipe is 500.8 uH.
(3) Resistance measurement before welding
After the electric melting welding machine is connected with the electric melting pipe fitting, a resistance measuring key additionally arranged on the operation panel is pressed, the welding machine outputs 3-5V voltage, the voltage and the current value on a welding line are measured, and the initial resistance value of the electric melting pipe fitting can be obtained according to the following formula
In the formula, RfThe initial resistance value of the electrofused pipe fitting, Ω; u shape0Measuring the voltage value V at two ends of the welding wire; i is0Is the current value on the weld line, A;
(4) control phase in welding process
The resistance value R of the electric melting pipe fitting obtained by the welding machine according to the parameter input and the resistance measurement stage is 1.05 omega, and the inductance value L is 500.8uH, full wave form effective voltage U of AC electric welding machine092V welding voltage U of electric melting pipe fittingAThe power factor fitting calculation formula is substituted by four parameters such as 60V, the power factor when welding is carried out by using an alternating current electric fusion welding machine is obtained by calculation, and the power factor is 0.9323
The output voltage of the DC inverter welding machine is compensated, the automatic compensation function of the output voltage of the DC inverter welding machine is realized, and the welding voltage U output by the actual DC inverter electric melting welding machineD＝57.9V。
Claims (5)
1. A method for automatically compensating the output voltage of a direct current inversion electric welding machine is characterized by comprising the following steps:
(1) obtaining power factor lambda of AC electric fusion welding machine for setting welding process parameters
According to the resistance value R and the inductance value L of the electric melting pipe fitting and the full-wave effective voltage U of the alternating current electric melting welding machine0AC welding voltage U specified by electric melting pipe fitting welding processACalculating a power factor lambda when the alternating current welding machine is used for setting; wherein the full waveform effective voltage U of the AC electric fusion welding machine0The effective value of full waveform voltage before chopping after the alternating current 220V voltage input by the alternating current electric fusion welding machine is reduced by a transformer is shown;
(1.1) calculating the effective value of the output voltage
According to the instantaneous value of the chopping voltage output by the alternating current welding machine:
and an effective voltage calculation formula, wherein the effective value of the output voltage is obtained by calculation:
each symbol in the above formula:
u (t) is the output voltage instantaneous value, V; u shape0The effective value V of full waveform voltage before chopping is carried out after the voltage of alternating current 220V input by the alternating current welding machine is reduced by a transformer; k is any natural number and is dimensionless; theta is the chopping angle, rad, of the output chopping voltage; ω 2 pi f, rad/s, where f is the alternating current frequency; u shapemIs the effective value of the output voltage, V; t is time, s; pi is the circumference ratio and is dimensionless;
(1.2) converting the voltage into a complex exponential form
Performing a complex exponential form transformation of the fourier transform on the output voltage:
wherein,
all the Fourier transform coefficients corresponding to k omega, and j is an imaginary number unit; tan (r) is-1Is an inverse function of tan, namely arctan, and has a value range (-pi, pi);
a0＝0
in the formula: a is-1,b-1,a0,b0,ak,bkAll are Fourier transform coefficients, and k is a natural number;
(1.3) converting the complex impedance into a complex exponential functional form
Wherein,
all the Fourier transform coefficients corresponding to k omega;
each symbol in the above formula:
z is the complex impedance of the electric melting pipe fitting; r is the resistance value of the electric melting pipe fitting, omega; l is the inductance value of the electric melting pipe fitting, H;
(1.4) calculating the effective value of the current
The complex exponential functional form of the current is:
according to a calculation formula of the current effective value, the current effective value is calculated as follows:
each symbol in the above formula:
i (t) is output powerInstantaneous value of the flow, a; i.e. imIs the effective value of the output current, a; i (t)ReA real part representing a complex form of the current; t is the period of the alternating current, s;
(1.5) calculating apparent Power and active Power
The apparent power is:
the active power is:
each symbol in the above formula: SP is the apparent power, W; RP is active power, W; u (t)ReA real part representing a complex form of the voltage;
(1.6) calculating the Power factor
The power factor is the ratio of active power to apparent power of the welder:
in the above formula: λ is a power factor;
(2) compensating output voltage of DC inverter welding machine
In order to make the actual direct current welding process equal to the alternating current welding power on the electric melting pipe fitting when determining the welding process parameters, the output voltage of the direct current inversion electric melting welding machine during welding is compensated:
the formula for ensuring equal welding power of the electric melting pipe fittings in the two processes is as follows:
the voltage compensation is determined by the following equation:
in the formula, P is the welding power of the electric melting pipe fitting in the welding process; u shapeDThe voltage compensation is carried out on the actual output voltage V of the direct current inversion electric fusion welding machine after voltage compensation; u shapeAAn alternating current welding voltage, V, specified for the electrofusion pipe fitting welding process; λ is the power factor obtained from the calculation of step (1).
2. A method for automatically compensating the output voltage of a direct current inversion electric welding machine is characterized by comprising the following steps:
(1) calculating the power factor lambda of the alternating current electric fusion welding machine for setting the welding process parameters by adopting a fitting formula:
λ＝[A1·ke 2+A2·ke+A3]·[B1·ke 3+B2·ke 2+B3·ke+B4]
in the formula A1、A2、A3、B1、B2、B3、B4Are all coefficients; u. ofeThe pressure regulating coefficient in the welding process; k is a radical ofeIs the inductance-resistance ratio; the expression of each coefficient is as follows:
in the formula, R is the resistance value of the electric melting pipe fitting, omega; l is the inductance value of the electric melting pipe fitting, H; u shape0The full waveform effective voltage of the alternating current welding machine; u shapeAAn alternating current welding voltage, V, specified for the electrofusion pipe fitting welding process;
(2) compensating output voltage of DC inverter welding machine
In order to make the actual direct current welding process equal to the alternating current welding power on the electric melting pipe fitting when determining the welding process parameters, the output voltage of the direct current inversion electric melting welding machine during welding is compensated:
the formula for ensuring equal welding power of the electric melting pipe fittings in the two processes is as follows:
the voltage compensation is determined by the following equation:
in the formula, P is the welding power of the electric melting pipe fitting in the welding process; u shapeDThe voltage compensation is carried out on the actual output voltage V of the direct current inversion electric fusion welding machine after voltage compensation; u shapeAAn alternating current welding voltage, V, specified for the electrofusion pipe fitting welding process; λ is the power factor obtained from the calculation of step (1).
3. The method according to claim 1 or 2, wherein before the operation of step (1) is performed, whether output voltage compensation is required or not is confirmed according to the type of welding process parameters of the electrofused pipe fittings; if the electric melting pipe fittings are specified to be welded by adopting direct current voltage, extra output voltage compensation is not needed; if the electric melting pipe fitting is welded by adopting alternating voltage, the output voltage needs to be compensated.
4. A method according to claim 1 or 2, wherein the electrofusion pipe is subjected to a welding voltage U as measured by an ac welderAIs 39.5V.
5. A DC inversion electric fusion welding machine with output voltage automatic compensation function comprises a processor for loading a control function module; characterized in that an output voltage automatic compensation module for implementing the method of claim 1 or 2 is loaded in the processor; the electric melting welding machine also comprises a resistance measuring circuit connected to the processor through a lead and used for measuring the resistance value of the electric melting pipe fitting; the operation panel of the electric fusion welding machine is provided with a selection key for compensating the output voltage, a selection key for measuring the resistance R of the electric fusion pipe fitting before welding and a selection key for inputting the full-wave effective voltage U of the alternating current electric fusion welding machine0And an input interface of the inductance value L of the electric melting pipe fitting.
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