Ap1:7 Arc Voltage Monitoring - ESAB Caddyt Arc 150i Service Manual

20AP1:7 Arc voltage monitoring
This circuit measures and scales the arc voltage to a suitable level for the
processor. 64 V arc voltage produces a voltage signal at the cathode of diode
D13, 5.1 V at version 1 of the board and 5.0 V at version 2.
MMA
When the current exceeds 10 A during welding start, the no--load voltage
control is deactivated. When the arc voltage exceeds 52 V, welding stops and
the no--load voltage control is activated.
The no--load voltage control holds the open--circuit voltage at about 70 V.
Machines with VRD function, Voltage Reduction Device, have an open--circuit
voltage of about 20 V.
TIG
The no--load voltage control is inactive in the TIG welding mode. The
open--circuit voltage is about 110 V. Arc voltages below 45 V are defined as
welding. Output voltage is produced only when TIG welding is in progress.
20AP1:8 TIG functions
Live TIG start, CaddyArc 150
This start method is used only by the CaddyArc 150.
Select TIG. The machine generates an output voltage.
S
Touch the electrode on to the workpiece. The machine produces a current
S
of about 6 A.
Lift the electrode from the workpiece. The arc strikes and the current
S
increases to 30 A.
When the arc voltage exceeds 8 V, the current increases / decreases to
S
the set current.
LiftArc TIG start
Output voltage is produced only when TIG welding is in progress.
Touch the electrode on to the workpiece.
S
Press the torch trigger. The machine produces a current of about 6 A.
S
Lift the electrode from the workpiece. The arc strikes and the current
S
increases to 30 A.
When the arc voltage exceeds 8 V, the current increases / decreases to
S
the set current.
HF TIG start
Output voltage is produced only when TIG welding is in progress. Arc voltages
below 45 V are defined as welding. See also: 10AP1 TIG board, on page 18.
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S0740 800 161/E061205/P66