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THEORY OF OPERATION
FIGURE E.3 – OUTPUT RECTIFICATION AND FEEDBACK CONTROL
HIGH FREQUENCY SPARK
ELECTRODE SENSE
PANEL | UPPER |
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| LOWER |
| DISPLAY |
| STATUS | |
CONTROL |
| CONTROL |
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SWITCHES |
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| BOARD |
| BOARD | ||||
PANEL |
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| PANEL |
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| ELECTRODE |
| SCR GATE COMMANDS |
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HIGH VOLTAGE | 115VAC |
| SENSE |
| 15VDC |
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TRANSFORMER | REMOTE |
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CIRCUIT | FEED - THRU | CONTROL |
| POWER | ||
| RECEPTACLE |
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| BOARD | TRIGGER | BOARD |
| BOARD |
GAS/WATER |
| REMOTE | INTERLOCK | |||
SOLENOIDS | 115VAC |
| COMMANDS |
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| INTERLOCK |
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| COMMANDS |
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| INTERLOCK |
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| 115VAC |
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| FANS 115VAC | 115VAC |
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| SNUBBER | |
| RECEPTACLE | CONTROL TRANSFORMER |
| BOARD | ||
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| 115VAC |
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INPUT | R |
| AC | DC- |
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CONTACTOR |
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E |
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| C |
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| C |
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| AC | DC+ | H |
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| O |
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| O |
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| N |
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| K |
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| POWER |
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| N |
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| WORK | ||
| E | FACTOR |
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| BOARDS | |
| CAPACITORS | POLARITY |
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| C |
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| T |
| SWITCH |
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| SHUNT |
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| START/ | MAIN |
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| ELECTRODE |
| STOP |
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| TRANSFORMER |
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| PILOT |
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| TRANSFORMER |
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| TRANSFORMER |
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OUTPUT RECTIFICATION AND
FEEDBACK CONTROL
The AC output from the main transformer secondary is rectified and controlled through the SCR bridge. Output current is sensed at the shunt as a low voltage signal and fed back to the control board. The control board compares the commands of the control panels, panel switches, and/or remote control with the shunt feedback signal and electrode sense lead. The appro- priate SCR gate firing commands are created by the control board and sent to the power board where the gate firing pulses are generated and applied through the snubber board to the SCR bridge. The control board controls the firing of the SCRs, which controls the output of the machine. See SCR Operation. The control board also powers and commands the display board and the status board.
The electrode sense, the remote control and the trig- ger signals are applied through the feed – thru board to the control board.
NOTE: Unshaded areas of Block Logic Diagram are the subject of discussion.
SQUARE WAVE TIG 355
