D.C. chopper with inductance control for welding
First Claim
1. In a multi-stage down chopper for arc welding by creating current flow between an electrode and a workpiece, said chopper including a D.C. input source, a first switching stage, with a first switch device and a first choke, said first stage selectively connects said D.C. input source across said electrode and workpiece at a controlled duty cycle and switching rate, a second switching stage, with a second switch device and a second choke, said second stage selectively connects said D.C. input source across said electrode and workpiece at said controlled duty cycle and switching rate, and a pulse width modulator for controlling said duty cycle and switching rate in accordance with a control signal, the improvement comprising:
- a magnetically permeable core and means for transformer coupling said first and second choke by winding said first and second chokes onto said core.
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Accused Products
Abstract
A multi-stage down chopper for arc welding by creating current flow between an electrode and a workpiece, the chopper includes a D.C. input source, a first switching stage, with a first switch device and a first choke, this first stage selectively connects the D.C. input source across the electrode and workpiece at a controlled duty cycle and switching rate and a second switching stage, with a second switch device and a second choke, the second stage also selectively connects the D.C. input source across the electrode and workpiece at the aforesaid controlled duty cycle and switching rate, wherein the chopper is improved by the first and second chokes onto a single core and by providing a minimum current override feedback circuit.
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Citations
24 Claims
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1. In a multi-stage down chopper for arc welding by creating current flow between an electrode and a workpiece, said chopper including a D.C. input source, a first switching stage, with a first switch device and a first choke, said first stage selectively connects said D.C. input source across said electrode and workpiece at a controlled duty cycle and switching rate, a second switching stage, with a second switch device and a second choke, said second stage selectively connects said D.C. input source across said electrode and workpiece at said controlled duty cycle and switching rate, and a pulse width modulator for controlling said duty cycle and switching rate in accordance with a control signal, the improvement comprising:
- a magnetically permeable core and means for transformer coupling said first and second choke by winding said first and second chokes onto said core.
- View Dependent Claims (2, 3, 4, 5, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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6. The improvement as defined in claim I wherein said switching devices are IGBTs.
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17. In a multi-stage down chopper for arc welding by creating current flow between an electrode and a workpiece, said chopper including a D.C. input source, a first switching stage, with a first switch device and a first choke, said first stage selectively connects said D.C. input source across said electrode and workpiece at a controlled duty cycle and switching rate, a second switching stage, with a second switch device and a second choke, said second stage selectively connects said D.C. input source across said electrode and workpiece at said controlled duty cycle and switching rate, and a pulse width modulator for controlling said duty cycle and switching rate in accordance with a control signal, the improvement comprising:
- a magnetically permeable core and means for transformer coupling said first and second choke by winding said first and second chokes onto said core, said control signal being an error signal representative of the difference between the voltage across said electrode and workpiece and a reference signal indicative of a selected desired arc voltage, and an override circuit for limiting said control signal to a value maintaining at least a minimum current across electrode and workpiece including means for controlling said minimum current as a function of the average current across said electrode and said workpiece.
- View Dependent Claims (18)
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19. In a multi-stage down chopper for arc welding by creating current flow between an electrode and a workpiece, said chopper including a D.C. input source, a first switching stage, with a first switch device and a first choke, said first stage selectively connects said D.C. input source across said electrode and workpiece at a controlled duty cycle and switching rate, a second switching stage, with a second switch device and a second choke, said second stage selectively connects said D.C. input source across said electrode and workpiece at said controlled duty cycle and switching rate, and a pulse width modulator for controlling said duty cycle and switching rate in accordance with a control signal the improvement comprising:
- a magnetically permeable core and means for transformer coupling said first and second choke by winding said first and second chokes onto said core, said control signal being an error signal representative of the difference between the current across said electrode and said workpiece and a reference signal indicative of a selected desired arc current and an override circuit for limiting said control signal to a value maintaining at least a minimum current across electrode and workpiece including means for controlling said minimum current as a function of the average current across said electrode and said workpiece.
- View Dependent Claims (20)
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21. In a down chopper for arc welding by creating a current flow between an electrode and a workpiece, said chopper including a D.C. input source, a switching stage with a switch device and a choke, said stage selectively connects said D.C. input source across said electrode and workpiece at a controlled duty cycle and switching rate, and a pulse width modulator for controlling said duty cycle and switching rate in accordance with a control signal, the improvement comprising:
- an override circuit for limiting said control signal to a value maintaining at least a minimum current across said electrode and workpiece.
- View Dependent Claims (22)
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23. In a down chopper for arc welding by creating a current flow between an electrode and a workpiece, said chopper including a D.C. input source, a switching stage with a switch device and a choke, said stage selectively connects said D.C. input source across said electrode and workpiece at a controlled duty cycle and switching rate, and a pulse width modulator for controlling said duty cycle and switching rate in accordance with a control signal, the improvement comprising:
- an override circuit for limiting said control signal to a value maintaining at least a minimum current across said electrode and workpiece including means for controlling said minimum current as a function of the average current across said electrode and said workpiece.
- View Dependent Claims (24)
Specification