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THEORY OF OPERATION
FIGURE E.3 – POWER MODULES AND FEEDBACK
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| DIODES | INPUT | CHOPPER MODULES |
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| CONTACTOR |
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| CR1 |
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| IGBT |
| FREEWHEELING DIODE |
| TO ELECTRODE | ||
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| CHOPPER MODULE |
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| CABLE | |
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| INPUT |
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| CHOKE |
| SHUNT | + |
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| CAPACITORS |
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| CURRENT FEEDBACK | |
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| ON/OFF |
| IGBT |
| FREEWHEELING DIODE |
| TO WELD CONTROL BOARD | ||
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| MODE |
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DC |
| SWITCH | 20 | CHOPPER MODULE |
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| (1/2) | ON/OFF | VOLTS | AMPS |
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POWER |
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| VDC |
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| MODE |
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| SWITCH |
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SOURCE |
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(EXTERNAL) |
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| ANALOG | SIGNALS |
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| DC |
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| WELD |
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| 40 |
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| VDC | CONTROL | VOLTAGES |
| REMOTE |
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| BUS |
| CONTROL | RECEPTACLE |
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| REGULATED |
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| POWER |
| POWER | FAN | BOARD |
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| SUPPLY |
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| CC SLOPE | ||
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| 40 VDC | ARC | OUTPUT | HOT |
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| 15 VDC |
| THERMAL |
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| FORCE | CONTROL | START | LIGHT |
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| CONTROL |
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| CR1 |
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| COIL |
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| PERIPHERAL |
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| BOARD |
| INDICATOR |
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| INPUT |
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| LIGHT |
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| - |
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| WORK |
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POWER MODULES AND FEED- BACK
The external DC source voltage is applied to parallel capacitors incorporated within each of the two Power (Chopper) Modules. These capacitors function as fil- ters and as power supplies for the IGBTs. See IGBT Operation in this section. The IGBTs act as high- speed switches operating at 20KHZ. These devices are switched on and off by the Weld Control Board through pulse width modulation gate signals. See Pulse Width Modulation in this section. This “chopped” DC output is applied through choke coils and a shunt to the welding output terminals. The
chokes function as current filters.
Output voltage and current feedback information is fed to the Weld Control Board. This information is sensed from the output terminal circuits and the shunt. The feedback information is processed by the Weld Control Board, which regulates output voltage and current.
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NOTE: Unshaded areas of Block Logic Diagram are the subject of discussion.