ESAB LAW 510 Service Manual page 21

5
SYNCHRONISING
Firing is synchronised to the mains by three zero crossing detectors, IC11;1, IC11;2
and IC11;13. The voltage between the phases at inputs E1, E2 and E3 is about 19 V
in the LAW 400/410 and about 25 V in the LAW 500/510.
6
THERMAL OVERLOAD CUTOUT
LED V7 lights if the cutout operates. The current through the LED is about 16 mA.
When the cutout operates the thyristor ignition pulses will be blocked.
LAW 400/500 with serial numbers of 434 . . . . . . .
The thermal overload cutout, ST1, is fitted to the thyristor heat sink (= cooling fins).
In the LAW 400, the cutout operates at a temperature of 60 _C, while in the LAW
500 it operates at 70 _C. It resets at 50 _C in both machines. See page 33 for fitting
instructions.
LAW 400/410 with serial numbers of 512 . . . . . . . and above
The thermal overload cutout, ST1, is fitted in the interphase transformer winding,
L1. It opens at a temperature of 140 _C, and closes at 110 _C.
LAW 500/510 with serial numbers of 512 . . . . . . . and above
The thermal overload cutout, ST1, is fitted in the inductor winding, L2. It opens at
a temperature of 160 _C, and closes at 130 _C.
claw0de1
claw0e12
- - 21 - -