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THEORY OF OPERATION
FIGURE E.6 – CONTROL BOARD, IGBT DRIVE AND MODULE
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S | FET | B | |
W | O | ||
I | CAP | A | |
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C | FET | ||
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LINE | INPUT |
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| CHARGE |
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SWITCH | RECTIFIER | R | P |
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| R | PWM SIGNAL |
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| 36VAC |
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| TAILOUT | PEAK | BACK- | PEAK | HOT | BACK- | WIRE | WIRE | |
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| CONTROL | CURRENT | START | GROUND | |||||
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| (STT II ONLY) | METER | METER | CONTROL CONTROL CONTROL | SWITCH | SWITCH | |||
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MAIN | 1 OHM |
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TRANSFORMER |
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CURRENT | IGBT | NEGATIVE |
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SENSOR | MODULE | OUTPUT |
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CHOKE |
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| E | P | O | RECEPTACLE |
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CURRENT FEEDBACK
IGBT
DRIVER
BOARD
VOLTAGE FEEDBACK
10VAC AND 6VAC
42VAC
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CONTROL BOARD, IGBT DRIVE AND MODULE
The control board monitors the directives of the various controls and compares these commands to the current and voltage feedback information received from the current sensor and voltage sensing receptacle. This data is processed and the suitable PWM signal is sent to the power board. (See Pulse Width Modulation discussion).
The control board also determines when the IGBT module should be switched OFF to reduce weld spat- ter and fumes. The appropriate signal is sent to the IGBT drive board which then applies, or removes, the gate drive signal to the IGBT module. When the IGBT module is in the OFF state, the welding current must pass through the one ohm resistance. This reduces the current and, subsequently, spatter and fumes.
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NOTE: Unshaded areas of Block Logic Diagram are the subject of discussion.
