High-precision welding arc voltage sampling circuit

Abstract

The utility model belongs to the technical field of welding automation, and particularly relates to a high-precision welding arc voltage sampling circuit which comprises a PLASA sampling loop and a TIG sampling loop. Sampling positive electrodes of the two sampling loops are connected with a welding tool; the sampling negative electrodes of the two sampling loops are connected with the negative electrode of the PLASA welding power source and the negative electrode of the TIG welding power source correspondingly. A PLASA sampling resistor is connected in series between a sampling positive electrode and a sampling negative electrode of the PLASA sampling loop, and a TIG sampling resistor is connected in series between a sampling positive electrode and a sampling negative electrode of the TIG sampling loop; the positive and negative ends of the PLASA sampling resistor and the TIG sampling resistor are respectively connected through a direct-current voltage converter, and the output end of the direct-current voltage converter is connected with the PLC analog quantity sampling module through an analog quantity isolation plate GLB1. According to the utility model, through the high-precision arc voltage sampling circuit, automatic welding equipment can obtain accurate welding arc voltage without the help of a special arc voltage acquisition module, and a hardware basis and a data basis are provided for automatic control of the welding arc voltage.

Description

TECHNICAL FIELD

[0001] The utility model belongs to welding automation technical field, specifically related to a high accuracy's welding arc voltage sampling circuit. BACKGROUND

[0002] When carrying out tungsten electrode argon arc welding (TIG) or plasma arc welding (PAW), a certain voltage will be formed between the welding torch and the workpiece, which is called arc voltage. The arc voltage is mainly determined by the arc length: the longer the arc length, the higher the arc voltage, and the shorter the arc length, the smaller the arc voltage. In the welding process, under the premise that the welding current is constant, the size of the welding arc voltage will greatly affect the final effect of welding. The reason is that the welding quality is closely related to the heat input (effective heat power), and the heat input P = η × U × I, wherein, U: arc voltage (V); I: welding current (A); η: power effective coefficient, 0.74~0.87 for stick arc welding, 0.77~0.90 for submerged arc welding, 0.68~0.85 for alternating current tungsten electrode argon arc welding, and 0.78~0.85 for direct current tungsten electrode argon arc welding, and the intermediate value is taken when not specified. In the automatic welding system, the welding arc voltage plays a key role in the welding quality, and the automatic control of the arc voltage is an essential function in the automatic welding system. The accurate sampling of the welding arc voltage is the premise of the automatic control of the arc voltage.

[0003] At present, some welding power supplies provide an automatic control interface, which can collect some welding-related data, such as real-time welding current, welding arc voltage, wire feeding speed, etc. By using the automatic control interface and cooperating with the sampling circuit, the welding voltage can be directly collected from the welding power supply. The automatic control interface matched with the welding power supply on the market is often expensive, and the requirements for the design personnel of the control system are also high. Some brands of welding power supply do not provide an automatic control interface. Therefore, it is particularly important to design a universal and high-precision welding arc voltage sampling circuit. UTILITY MODEL CONTENT

[0004] To solve the above technical problems, the utility model provides a kind of high-precision welding arc voltage sampling circuit, and the arc voltage during welding is obtained by arc voltage sampling circuit, to realize the arc voltage automatic control function of automatic welding equipment.

[0005] To achieve the above purpose, the utility model adopts the following technical solutions:

[0006] The application relates to a high-precision arc voltage sampling circuit, which comprises a PLASMA sampling circuit and a TIG sampling circuit; the sampling positive poles of the two sampling circuits are connected with a welding tool; the sampling negative poles of the two sampling circuits are connected with the negative poles of a PLASMA welding power source and a TIG welding power source respectively; a PLASMA sampling resistor is connected in series between the sampling positive pole and the sampling negative pole of the PLASMA sampling circuit; a TIG sampling resistor is connected in series between the sampling positive pole and the sampling negative pole of the TIG sampling circuit; the positive and negative poles of the PLASMA sampling resistor and the TIG sampling resistor are connected through DC voltage converters respectively, and the output ends of the DC voltage converters are connected with a PLC analog quantity sampling module through an analog quantity isolation board GLB1.

[0007] Further, the sampling positive pole of the PLASMA sampling circuit is connected with the welding tool through an inductor H6, and the sampling positive pole of the TIG sampling circuit is connected with the welding tool through an inductor H14; the sampling negative pole of the PLASMA sampling circuit is connected with the negative pole of the PLASMA welding power source through the inductors H1, H2 and H3 connected in series, and the sampling negative pole of the TIG sampling circuit is connected with the negative pole of the TIG welding power source through the inductors H9, H10 and H11 connected in series.

[0008] Further, the PLASMA sampling resistor is composed of a power resistor R1 and a pressure-sensitive resistor R2 connected in series; and the TIG sampling resistor is composed of a power resistor R3 and a pressure-sensitive resistor R4.

[0009] Further, the sampling input circuit of the DC voltage converter is connected in parallel with the PLASMA sampling resistor and the TIG sampling resistor through the normally closed contact of a high-frequency relay KH10.

[0010] Further, the normally closed contact of the high-frequency relay KH10 is connected with inductors in series at both ends.

[0011] Further, the normally open contact of a sampling isolation relay KH17 is connected in series between the DC voltage converter BHQ1 and the high-frequency relay KH10.

[0012] The automatic welding equipment can obtain accurate welding arc voltage without the help of a special arc voltage collection module through the high-precision arc voltage sampling circuit, and the hardware foundation and data basis are provided for the automatic control of the welding arc voltage. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 : high-precision arc voltage sampling circuit diagram. DETAILED DESCRIPTION

[0014] The application will be described in detail below in combination with the drawings and embodiments.

[0015] The welding arc voltage is the voltage between the welding torch and the workpiece during welding. During normal welding, the welding torch is connected to the negative pole of the welding power source, and the workpiece is connected to the positive pole of the welding power source. The current flows from the workpiece to the welding torch, and the electrons flow from the welding torch to the workpiece, thereby achieving the heating effect of the welding power source on the workpiece. Therefore, the negative pole of the sampling circuit can be connected to the negative pole of the welding power source, and the positive pole of the sampling circuit can be connected to the workpiece.

[0016] The collected voltage is protected by multiple series-connected inductors, pressure-sensitive resistors, and power resistors, and then passes through a DC voltage converter and an analog quantity isolation board to finally reach the PLC analog quantity sampling module. After analog-to-digital conversion, the collected voltage can be converted into a digital quantity, and after calculation, the welding arc voltage can be obtained.

[0017] As shown in Figure 1 A high-precision welding arc voltage sampling circuit, P1 is a PLASMA welding power source, P2 is a TIG welding power source, the sampling circuit includes a PLASMA sampling loop and a TIG sampling loop, the sampling positive poles of the two sampling loops are connected to the welding tool, specifically, the sampling positive pole of the PLASMA sampling loop is connected to the welding tool through inductor H6, and the sampling positive pole of the TIG sampling loop is connected to the welding tool through inductor H14; the sampling negative poles of the two sampling loops are connected to the negative poles of the welding power source, specifically, the sampling negative pole of the PLASMA sampling loop is connected to the negative pole of the PLASMA welding power source through series-connected inductors H1, H2, and H3, and the sampling negative pole of the TIG sampling loop is connected to the negative pole of the TIG welding power source through series-connected inductors H9, H10, and H11.

[0018] In a welding system, high-frequency arc starting is generally used, so the welding arc voltage sampling circuit is often disturbed by high-frequency signals. High-frequency signals often exist in the form of high voltage, alternating current, and constantly changing amplitude, which can damage the sampling circuit. By using the characteristic of inductors to hinder current changes, high-frequency signals can be effectively suppressed.

[0019] The PLASMA sampling resistor composed of power resistor R1 and pressure-sensitive resistor R2 is connected in series between the sampling positive and negative poles of the PLASMA sampling loop, and the power resistor R1 and the pressure-sensitive resistor R2 are connected in series. The TIG sampling resistor composed of power resistor R3 and pressure-sensitive resistor R4 is connected in series between the sampling positive and negative poles of the TIG sampling loop, and the power resistor R3 and the pressure-sensitive resistor R4 are connected in series. The PLASMA sampling resistor and the TIG sampling resistor are connected in parallel to the sampling circuit, which can clamp the voltage to a relatively fixed voltage value, thereby protecting the subsequent circuit.

[0020] When the arc is started, the high frequency voltage can reach 10000V. The power resistor R1 and R3 are selected as 10K / 2W. Thus the maximum current through the resistor can be calculated as 10000 / 10000A, i.e. 1A. By using the principle of series voltage division, the voltage loaded on the voltage sensitive resistor is much smaller than the selected 820V. Thus the power resistor of 10K / 2W and the voltage sensitive resistor of 820V are selected as appropriate.

[0021] When the arc is started, the high frequency voltage can reach 10000V. The power resistor R1 and R3 are selected as 10K / 2W. Thus the maximum current through the resistor can be calculated as 10000 / 10000A, i.e. 1A. By using the principle of series voltage division, the voltage loaded on the voltage sensitive resistor is much smaller than the selected 820V. Thus the power resistor of 10K / 2W and the voltage sensitive resistor of 820V are selected as appropriate.

[0022] When the arc is started, the high frequency voltage can reach 10000V. The power resistor R1 and R3 are selected as 10K / 2W. Thus the maximum current through the resistor can be calculated as 10000 / 10000A, i.e. 1A. By using the principle of series voltage division, the voltage loaded on the voltage sensitive resistor is much smaller than the selected 820V. Thus the power resistor of 10K / 2W and the voltage sensitive resistor of 820V are selected as appropriate.

[0023] When the arc is started, the high frequency voltage can reach 10000V. The power resistor R1 and R3 are selected as 10K / 2W. Thus the maximum current through the resistor can be calculated as 10000 / 10000A, i.e. 1A. By using the principle of series voltage division, the voltage loaded on the voltage sensitive resistor is much smaller than the selected 820V. Thus the power resistor of 10K / 2W and the voltage sensitive resistor of 820V are selected as appropriate.

[0024] V = D ÷ 27648 x 10 x 10 x K (V)

[0025] Where K is the arc voltage calibration coefficient, which can calibrate the error between the theoretical value and the actual value, and the value range is generally between 0.85 and 1.15.

[0026] As shown in Figure 1 The DC voltage converter BHQ1 and BHQ2 sampling input circuit are connected in parallel with the PLASMA sampling resistor and the TIG sampling resistor through the normally closed contact of the high frequency relay KH10. The high frequency relay KH10 can effectively avoid the impact of the high frequency voltage (up to ten thousand volts) on the sampling circuit during the arc starting process of the TIG welding torch, and plays the most direct protection role.

[0027] In order to better protect the sampling module, avoid high frequency to cause damage to the sampling module, inductance H4, inductance H7, inductance H12, inductance H15, inductance H5, inductance H8, inductance H13, inductance H16 are connected in series in front of the DC voltage converter as the last protection. Inductance H4, inductance H7, inductance H12, inductance H15, inductance H5, inductance H8, inductance H13, inductance H16 are connected in series between the normally closed contact of high frequency relay KH10, specifically, inductance H7, inductance H8 are connected in series between the normally closed contact of high frequency relay KH10 on the input positive (IN+) line of DC voltage converter BHQ2; inductance H4, inductance H5 are connected in series between the normally closed contact of high frequency relay KH10 on the input negative (IN-) line of DC voltage converter BHQ2; inductance H15, inductance H16 are connected in series between the normally closed contact of high frequency relay KH10 on the input positive (IN+) line of DC voltage converter BHQ1; inductance H12, inductance H13 are connected in series between the normally closed contact of high frequency relay KH10 on the input negative (IN-) line of DC voltage converter BHQ1.

[0028] The normally open contact of sampling isolation relay KH17 is also connected in series in the TIG sampling circuit. Sampling isolation relay KH17 is connected in series between DC voltage converter BHQ1 and high frequency relay KH10. When the coil of KH10 loses power, KH17 can be closed by program control delay, which can prevent residual high frequency from causing damage to the subsequent sampling circuit.

Claims

1. A high-precision welding arc voltage sampling circuit, characterized in that, The sampling circuit comprises a PLASMA sampling circuit and a TIG sampling circuit; the sampling positive pole of the two sampling circuits is connected with a welding tool; the sampling negative pole of the two sampling circuits is connected with the negative pole of a PLASMA welding power source and a TIG welding power source respectively; the sampling positive pole and the sampling negative pole of the PLASMA sampling circuit are connected in series with a PLASMA sampling resistor, and the sampling positive pole and the sampling negative pole of the TIG sampling circuit are connected in series with a TIG sampling resistor; the positive pole and the negative pole of the PLASMA sampling resistor and the TIG sampling resistor are connected through a direct current voltage converter respectively, and the output end of the direct current voltage converter is connected with a PLC analog quantity sampling module through an analog quantity isolation board GLB1.

2. The high-precision arc voltage sampling circuit of claim 1, wherein, The sampling positive pole of the PLASMA sampling circuit is connected with the welding tool through an inductor H6, and the sampling positive pole of the TIG sampling circuit is connected with the welding tool through an inductor H14; the sampling negative pole of the PLASMA sampling circuit is connected with the negative pole of the PLASMA welding power source through the inductors H1, H2 and H3 connected in series, and the sampling negative pole of the TIG sampling circuit is connected with the negative pole of the TIG welding power source through the inductors H9, H10 and H11 connected in series.

3. The high-precision arc voltage sampling circuit of claim 1, wherein, The PLASMA sampling resistor is composed of a power resistor R1 and a pressure sensitive resistor R2 connected in series; and the TIG sampling resistor is composed of a power resistor R3 and a pressure sensitive resistor R4.

4. The high-precision arc voltage sampling circuit of claim 1, wherein, The sampling input circuit of the direct current voltage converter is connected in parallel with the PLASMA sampling resistor and the TIG sampling resistor through the normally closed contact of a high frequency relay KH10 respectively.

5. The high-precision arc voltage sampling circuit of claim 4, wherein, The normally closed contact of the high frequency relay KH10 is connected in series with an inductor at both ends respectively.

6. The high-precision arc voltage sampling circuit of claim 4, wherein, The normally open contact of a sampling isolation relay KH17 is connected in series between the direct current voltage converter BHQ1 and the high frequency relay KH10.

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