Tweco Troubleshooting Power Supply - Manual (Page 15)

15
If code set just after arc transfer:
• Unit pilots OK and can perhaps cut at lower currents but higher current will
set 2-2 shortly after transfer. Wires to power supply or wires from fuse box to
mains too small for the current cause voltage drop as current rises. Voltage
will measure OK when not trying to cut.
Poor Power Quality:
• Voltage can go out of range momentarily from a few ms. to a couple seconds
then recover. Inverter fans are powered from a DC supply. Because of the
charge in the DC supplies capacitors the fans will run for up to a few seconds
after power is removed. If input voltage goes out of the range for a very short
time then recovers it may appear that the fans didn’t shut off at all.
AC Power Issues
For voltage drooping under load check the wiring to the power supply, both
the fuse box to supply and even more important because they are usually longer,
the wires coming to the fuse box from the main input are rated for the current
draw. Verify that no other equipment that also draws current is on the same
circuit. Verify that the factory’s main transformer can handle the increased load,
especially if they didn’t have a plasma there before.
Momentary voltage dropouts or surges are very hard to find. Often requires
testing with a recording line monitor that remains in place for a few hours or
days. All measurements below will appear OK because they are only off at the
time of disturbance. This can lead one to think the CCM is giving false codes
when in fact the system is responding correctly to voltage that is out of range if
only momentarily.
Power Supply PCBs
Simplified circuit: