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| THEORY OF OPERATION | ||||||||||||
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| FIGURE E.4 — OUTPUT CIRCUITS |
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| ARC |
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| TRIGGER | WIRE |
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| VOLTAGE |
| RECEPTACLE | SPEED |
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| CONTROL |
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| CONTROL |
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Return
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CIRCUIT LINE
BREAKER SWITCH
INPUT
RECEPTACLE
FAN
MOTOR
CONTROL | GAS | |
BOARD | ||
SOLENOID | ||
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| WIRE | |
| FEED | |
| MOTOR | |
| VOLTAGE FEEDBACK & | |
| MOTOR POWER |
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MAIN |
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| MAIN |
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TRANSFORMER |
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| BRIDGE |
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CHOKE
+
OUTPUT
TERMINALS
-
OUTPUT CONTROL, RECTIFICATION & VOLTAGE FEEDBACK
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The AC voltage that is applied to the main transformer primary is controlled at the control board by two SCRs (Silicon Controlled Rectifiers). The SCRs are controlled by a pulse signal developed on the control board. The control board compares the commands of the arc volt- age control with the voltage feedback signal. (The Arc Voltage Control may be either a continuous control or a selector switch, depending on the model of the machine).
The board circuitry then sends a pulse to turn on the SCRs. In this manner, the voltage applied to the pri- mary of the transformer is varied and controlled. This controlled voltage is reflected at the transformer sec- ondary winding and is applied to the rectifier diode bridge. This rectified DC voltage is filtered by the out- put capacitor and choke circuit and is applied to the machine’s output terminals.
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NOTE: Unshaded areas of Block Logic Diagram are the subject of discussion
