THEORY OF OPERATION
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CHOPPER TECHNOLOGY
FUNDAMENTALS
The new era of welding machines such as the Commander 300, employ a technology whereby a DC source is turned on and off (chopped up) at high speed, then smoothed through an inductor to control an arc.
Hence the name “Chopper.” The biggest advantage of the chopper technology is the
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3 PHASE |
| DC RECTIFIER |
| SOLID STATE |
| INDUCTOR |
| ARC | |
ALTERNATOR |
| AND FILTER |
| SWITCH |
| AND DIODE |
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ARC
CONTROL
In this system, the engine drives a | the switch on and off, current in the inductor and the |
nator, which generates power that is rectified and fil- | arc can be controlled. The following diagram depicts |
tered to produce about 85VDC. The current is | the current flow in the system when the switch is open |
applied through a solid state switch to an inductor. By | and closed: |
turning |
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| INDUCTOR | |
| SWITCH | |
85VDC | ARC | |
DIODE | ||
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| CURRENT WITH SWITCH OPEN | |
| CURRENT WITH SWITCH CLOSED |
When the switch is closed, current is applied through | varying the ratio of on time versus off time of the switch | |
the inductor to the arc. When the switch opens, current | (Duty Cycle), | the current applied to the arc is con- |
stored in the inductor sustains flow in the arc and | trolled. This | is the basis for Chopper Technology: |
through the diode. The repetition rate of switch closure | Controlling the switch in such a way as to produce | |
is 20Khz, which allows | superior welding. | |
