Weld circuit calibration for arc voltage compensation

Patent metadata

Field	Value
Publication number	US-12440912-B2
Application number	US-202217588850-A
Country	US
Kind code	B2
Filing date	Jan 31, 2022
Priority date	Jan 25, 2022
Publication date	Oct 14, 2025
Grant date	Oct 14, 2025

Abstract

A method is performed in a welding or cutting system including a power supply configured to deliver current pulses through a weld circuit to a contact tip extending from a welding torch to create an arc on a workpiece. The method includes: while the contact tip is shorted to the workpiece to set an arc voltage equal to zero: sampling a current pulse to produce current values; and at a voltage sense point, on the power supply or the weld circuit, that is spaced-apart from the welding torch, sampling a voltage pulse associated with the current pulse to produce voltage values that differ from the arc voltage due to an electrical circuit parameter of the weld circuit; and computing a value of the electrical circuit parameter based on the current values, the voltage values, and the arc voltage equal to zero.

First claim

What is claimed is:

1. A method performed in a welding or cutting system, including a power supply configured to deliver current pulses through a weld circuit to a contact tip extending from a welding torch to create an arc on a workpiece, comprises:
while the contact tip is shorted to the workpiece to set an arc voltage equal to zero:
sampling, on a current pulse having a current ramp and a current peak that is relatively flat compared to the current ramp, the current peak to produce current values; and
at a voltage sense point, on the power supply or the weld circuit, that is spaced-apart from the welding torch, sampling, on a voltage pulse associated with the current pulse and that has a voltage ramp and a voltage peak that is relatively flat compare to the voltage ramp, the voltage peak to produce voltage values that differ from the arc voltage due to an electrical circuit parameter of the weld circuit; and

computing a value of the electrical circuit parameter based on the current values, the voltage values, and the arc voltage equal to zero.

2. The method of claim 1 , further comprising:
while the contact tip is shorted to the workpiece to set the arc voltage equal to zero:
sampling a second current pulse to produce second current values; and
at the voltage sense point, sampling a second voltage pulse associated with the second current pulse to produce second voltage values that differ from the arc voltage due to the electrical circuit parameter and a second electrical circuit parameter of the weld circuit; and

computing a value of the second electrical circuit parameter based on the electrical circuit parameter, the second current values, the second voltage values, and the arc voltage equal to zero.

3. The method of claim 1 , wherein:
sampling the current pulse includes digitizing the current values to produce digitized current values;
sampling the voltage pulse includes digitizing the voltage values to produce digitized voltage values; and
the method further comprises:
filtering the digitized current values with a first digital filter having a first low pass filter response, to produce filtered digitized current values as the current values; and
filtering the digitized voltage values with a second digital filter having a second low pass filter response, to produce filtered digitized voltage values as the voltage values,
wherein computing includes computing the value of the electrical circuit parameter based on the filtered digitized current values, the filtered digitized voltage values, and the arc voltage equal to zero.

4. The method of claim 3 , wherein the first low pass filter response and the second low pass filter response match each other.

5. The method of claim 1 , wherein the electrical circuit parameter is a resistance of the weld circuit, and computing includes computing a value of the resistance as the value.

6. The method of claim 1 , wherein the electrical circuit parameter is an inductance of the weld circuit, and computing includes computing a value of the inductance as the value.

7. The method of claim 1 , wherein the voltage values differ from the arc voltage that is set equal to zero by a voltage drop that is a function of the electrical circuit parameter and current in the weld circuit, and computing includes iteratively testing successive candidate values of the electrical circuit parameter to find, as the value of the electrical circuit parameter, one of the successive candidate values that would cause the voltage drop in the weld circuit.

8. The method of claim 7 , wherein computing further includes:
using a candidate value of the electrical circuit parameter, computing a voltage drop that would occur based on the candidate value of the electrical circuit parameter and a particular current value among the current values, and testing whether a difference between the computed voltage drop and a particular voltage value among the voltage values that corresponds to the particular current value is zero; and
when the difference is not zero, selecting a next candidate value of the electrical circuit parameter that would drive the difference closer to zero, and repeating computing and testing based on the next candidate value.

9. The method of claim 1 , further comprising, during a weld operation during which the contact tip is not shorted to the workpiece:
sampling a weld current pulse configured to create an arc on the workpiece, to produce weld current values;
at the voltage sense point, sampling a weld voltage pulse corresponding to the weld current pulse, to produce weld voltage values; and
compensating the weld voltage values based on the weld current values and at least the value of the electrical circuit parameter, to produce compensated voltage values that accurately reflect the arc voltage.

10. An apparatus for welding or cutting comprising:
a power supply configured to deliver current pulses through a weld circuit to a contact tip extending from a welding torch to create an arc on a workpiece; and
a controller coupled to the power supply and configured to perform:
while the contact tip is shorted to the workpiece to set an arc voltage equal to zero:
sampling, on a current pulse having a current ramp and a current peak that is relatively flat compared to the current ramp, the current peak to produce current values; and
at a voltage sense point, on the power supply or the weld circuit, that is spaced-apart from the welding torch, sampling, on a voltage pulse associated with the current pulse and that has a voltage ramp and a voltage peak that is relatively flat compare to the voltage ramp, the voltage peak to produce voltage values that differ from the arc voltage due to an electrical circuit parameter of the weld circuit; and

computing a value of the electrical circuit parameter based on the current values, the voltage values, and the arc voltage equal to zero.

11. The apparatus of claim 10 , wherein the controller is further configured to perform:
while the contact tip is shorted to the workpiece to set the arc voltage equal to zero:
sampling a second current pulse to produce second current values; and
at the voltage sense point, sampling a second voltage pulse associated with the second current pulse to produce second voltage values that differ from the arc voltage due to the electrical circuit parameter and a second electrical circuit parameter of the weld circuit; and

computing a value of the second electrical circuit parameter based on the electrical circuit parameter, the second current values, the second voltage values, and the arc voltage equal to zero.

12. The apparatus of claim 10 , wherein the controller is configured to perform:
sampling the current pulse by digitizing and then low pass filtering the current values to produce filtered digitized current values as the current values;
sampling the voltage pulse by digitizing and then filtering the voltage values to produce filtered digitized voltage values as the voltage values; and
computing by computing the value of the electrical circuit parameter based on the filtered digitized current values, the filtered digitized voltage values, and the arc voltage equal to zero.

13. The apparatus of claim 10 , wherein the electrical circuit parameter is a resistance of the weld circuit, and the controller is configured to perform computing by computing a value of the resistance as the value.

14. The apparatus of claim 10 , wherein the electrical circuit parameter is an inductance of the weld circuit, and the controller is configured to perform computing by computing a value of the inductance as the value.

Assignees

• Esab Ab

Inventors

• Juliusson David

Classifications

• B23K9/1062

  with computing means · CPC title

• B23K9/0956

  using sensing means, e.g. optical · CPC title

• B23K9/091 Primary

  characterised by the circuits · CPC title

• B23K9/09

  Arrangements or circuits for arc welding with pulsed current or voltage · CPC title

• B23K9/0953 Primary

  using computing means · CPC title