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THEORY OF OPERATION
FIGURE E.3 – PRECHARGE AND PROTECTION
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| WORK |
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| NOZZLE |
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| POWER BOARD |
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| ELECTRODE |
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| MAIN |
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| TORCH |
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| CR 1 |
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| TRANSFORMER | OUTPUT BOARD |
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| RELAY |
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INPUT |
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| IGBT |
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LINE | INPUT |
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SWITCH | RECTIFIER |
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| T |
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| R |
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| CAPACITOR |
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| CHOKE | E |
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| E | IGBT |
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| PILOT |
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| TRANSISTOR |
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| C | IGBT |
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| CURRENT |
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| TRANSFORMER |
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| TRIGGER & SAFETY | ||
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| I | CAPACITOR |
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| AIR |
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| SOLENOID |
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| IGBT |
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| AIR | P |
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| PRESSURE | O |
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| SWITCH | T | CR 1 | IGBT |
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| "A" | E | RELAY |
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| C | DRIVE | GATE |
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| T | SIGNALS |
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| SIGNAL |
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| ELECTRODE & TRANSFER |
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| CURRENT FEEDBACK |
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| E | N | SIGNAL |
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| PILOT ENABLE |
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| CONTROL BOARD | ELECTRODE SOLENOID ENABLE |
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| AIR SOLENOID ENABLE |
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| 18/36VAC |
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| R | A | T | S |
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| E | I | H | A |
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| THERMOSTATS | R | E | F |
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| L | R | E |
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| D | M | T |
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| Y | O | A | Y |
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FAN |
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| W | L |
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| OUTPUT |
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MOTORS |
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| CONTROL |
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| DISPLAY BOARD |
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| 12VAC |
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| 24VAC |
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AUXILIARY
TRANSFORMER
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PRECHARGE AND PROTECTION
The input voltage is rectified by the input rectifier. The resultant DC voltage is applied, through the reconnect switch, to the power board. The power board contains precharging circuitry for the safe charging of the input filter capacitors. Once the capacitors are precharged and balanced the control board activates the CR1 input relay. This connects full input power to the filter capacitors. When the filter capacitors are fully charged they act as power supplies for the IGBT switching circuit. The Insulated Gate Bipolar Tran- sistors supply the main transformer primary winding with DC current flow. See IGBT Operation discussion and diagrams in this section.
The power board also monitors the filter capacitors for voltage balance and under or overvoltage. If either should occur, the appropriate signal is sent to the con- trol board to deactivate the CR1 input relay. The machine output will also be disabled.
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NOTE: Unshaded areas of Block Logic Diagram are the subject of discussion.
