Lincoln Electric SVM129-B Protective Circuits, Overload Protection, Thermal Protection

E-10 E-10

THEORY OF OPERATION

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PROTECTIVE CIRCUITS

Protective circuits are designed into the Invertec machine to sense trouble and shut down the machine before the trouble damages the internal machine com- ponents. Both overload and thermal protection circuits are included.

OVERLOAD PROTECTION

The machine is electrically protected from producing abnormally high output currents due to short electrode “stick-out” or the nozzle shorting to the work. Should the output current exceed 500 amps, an electronic pro- tection circuit will reduce the current to zero amps. Five seconds after the “short” is removed the Invertec STT will produce normal output.

A protection circuit is included to monitor the voltage across input filter capacitors. In the event that the capacitor voltage is too high, the protection circuit will prevent output. The protection circuit may prevent out- put, if any of these circumstances occur:

1.Capacitor conditioning is required

(Required if machine has been off for prolonged periods of time.)

2.Line surges over 500 VAC

3.Internal Component damage

4.Improper connections

THERMAL PROTECTION

Thermostats protect the machine from excessive oper- ating temperatures. Excessive temperatures may be caused by a lack of cooling air or operating the machine beyond the duty cycle and output rating. If excessive operating temperature should occur, the thermostat will prevent output voltage or current. The meter will remain on during this time. (In addition, the yellow thermo LED will light.)

Thermostats are self-resetting once the machine cools sufficiently. If the thermostat shutdown was caused by excessive output or duty cycle and the fan is operating normally, the Power Switch may be left on and the reset should occur within a 15-minute period. If the fan is not turning or the air intake louvers were obstructed, then the power must be switched off for 15 minutes in order to reset. The fan problem or air obstruction must also be corrected.

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INVERTEC STT