Claims
- 1. A method of protecting an invertor comprising the steps of:
- providing a first dc signal;
- inverting the first dc signal;
- providing a second dc signal;
- connecting the first and second dc signals in an additive arrangement across the input of the inverter, thereby clamping the voltage applied to the inverter to the sum of the first and second dc signals; and
- clamping the voltage across the invertor to a level more than twice that of the first dc signal.
- 2. An ac/dc GTAW power supply for providing an output to an arc comprising:
- a dc source of current having a dc voltage level;
- an inverter connected to receive the dc source of current and capable of providing an ac output to the arc and further capable of providing an electrode negative dc output to the arc and further capable of providing an electrode positive dc output to the arc;
- means for providing a period of electrode positive dc energy at an initiation of the welding process and prior to the provision of electrode negative output to the arc;
- means for providing a period of electrode positive dc energy at the initiation of the welding process and prior to the provision of ac output to the arc; and
- means for clamping the voltage across the inverter to a level more than twice that of the dc voltage level.
- 3. The power supply of claim 2 wherein the dc source of current is adjustable and comprises;
- a source of dc voltage provided between first and second buses;
- at least one switch having a control input, wherein the switch is connected to the first bus;
- a current gate connected between the switch and the second bus; and
- at least one inductor having a first and second end, wherein the first end is connected to the node common to the switch and the current gate, wherein the output of the converter is across the second bus and the second end of the inductor;
- and a variable frequency saw tooth wave generator connected to the control input, wherein the switch is turned on at the frequency of the saw tooth wave, and further wherein the frequency is inversely related to the desired current output magnitude.
- 4. A method of providing a dc output to an arc for GTAW welding comprising:
- providing a dc current having a first dc voltage level;
- inverting the dc current to providing a period of electrode positive dc energy at an initiation of the welding process and prior to the provision of electrode negative dc output to the arc; and
- clamping the voltage across the invertor to a level more than twice that of the first dc voltage level.
- 5. A method of starting an ac GTAW arc comprising:
- providing a dc current having a first dc voltage level;
- inverting the dc current to providing an extended period of electrode positive dc energy to the arc at an initiation of the welding process;
- thereafter providing an ac output to the arc; and
- clamping the voltage across the invertor to a level more than twice that of the first dc voltage level.
Parent Case Info
This is a continuation of U.S. Ser. No. 08/206,057 filed on Mar. 3, 1994.
US Referenced Citations (15)
Foreign Referenced Citations (2)
Number |
Date |
Country |
0438323A1 |
Jul 1991 |
EPX |
0580919A1 |
Feb 1994 |
EPX |
Non-Patent Literature Citations (1)
Entry |
Welding Handbook, Chapter 3, Gas Tungsten Arc Welding, pp. 74-107, American Welding Society (1991). |
Continuations (1)
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Number |
Date |
Country |
Parent |
206057 |
Mar 1994 |
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