THEORY OF OPERATION |
TOC | TOC | FIGURE E.2 — INPUT LINE VOLTAGE AND MAIN TRANSFORMER. | ||||||
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Section | Master |
| GAS | FAN |
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| SOLENOID | MOTOR |
| WIRE |
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| DRIVE |
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| MOTOR |
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to | to | WIRE |
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SPEED |
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Return | Return |
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ARC | CONTROL |
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VOLTAGE | BOARD |
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| TACH |
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| 115 VAC |
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| GUN TRIGGER |
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| RECTIFIER |
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| DIODE | G |
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| FEEDBACK |
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| BRIDGE |
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| 30 VAC |
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| LINE | SNUBBER | S |
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| BOARD |
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| SWITCH |
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| N |
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TOC | TOC |
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Section | Master |
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| POWER | C | F | OUTPUT | POSITIVE |
RECONNECT |
| ENHANCEMENT | A | CHOKE | ||||
| TERMINAL | |||||||
MAIN |
| CHOKE | P | E |
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TRANSFORMER | SCR |
| A | E |
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to | to |
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| C | D |
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| RECTIFIER |
| I | B |
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Return | Return |
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| T | A |
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| O | C |
| NEGATIVE | ||
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| R | K |
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| TERMINAL | ||||
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| SHUNT |
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| INPUT LINE VOLTAGE | gate drive circuitry. The weld power windings connect | |
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| AND MAIN TRANSFORMER | to the main SCR Rectifier and via the Snubber Board | |
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| to the Rectifier Diode Bridge. This AC voltage is recti- | ||
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| The desired single phase input power is connected to | fied and then regulated by the control board. The | |
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| resultant +15 VDC and +5 VDC voltages supply power | ||
TOC | TOC | the POWER MIG 255 through a line switch located on | to the control board circuitry. The 115 VAC winding (X8 | |
the front panel. | and X9) supplies power, through the control board, to | |||
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Section | Master | A reconnect panel allows the user to configure the | the thermostatically controlled fan motor. | |
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| machine for the desired input voltage. This AC input | The fan is designed to come on automatically when | |
to | to | voltage is applied to the primary of the main trans- | weld arc is established. The fan will stay on for a mini- | |
former. The main transformer converts the high | mum of six minutes after the weld arc is terminated. | |||
Return | Return | |||
voltage, low current input power to a low voltage, high | The fan will also stay on when the machine’s welding | |||
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| current output. In addition, the main transformer also | and feeding are disabled during thermostatic | |
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| has an isolated center tapped 30 VAC auxiliary winding | perature protection. (See Thermal and Overload | |
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| that supplies power to the Control Board for the SCR | Protection.) |
Section TOC | Master TOC |
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to | to | NOTE: Unshaded areas of Block Logic | |
Diagram are the subject of discussion | |||
Return | Return | ||
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POWER MIG 255 | |||
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