Tweco 300 XT Auto-Cut 400V - Manual (Page 139)

AUTO-CUT 300 XT
Manual 0-5290 APPENDIX A-57
Troubleshooting:
1. If the fault is L239 applying START will clear the fault unless it becomes active again. An occasional prob-
lem may be due to incoming voltage swells (voltage increases lasting from ½ cycle to as much as a minute).
Usually, if the plasma is at fault the problem will be present all the time.
2. It is unlikely that an open connection on the J61 jumper would result in a 239 fault, more likely to be a Volt-
age Mismatch fault. However, if it’s intermittent at exactly the right time, perhaps not fully plugged in, it
could possibly show up as 239. Check J61.
3. If the incoming voltage is OK and the problem persists it may be the System Bias board, the CCM or the
connection between J62 and J27.
a. If the incoming voltage is OK and D4 is on or signal “AC V HIGH b” on J62-6 is “high” (about 24VDC,
relative to TP1 or J62-8 ) the System Bias board is defective.
b. If D4 is not on and the signal “AC V HIGH b” on J62-6 is “low” (about 10-14VDC, relative to TP1 or
J62-8) then System Bias is OK and problem is in the CCM.
c. If J62-6 is near zero volts there may be bad connection between J62-6 and J27-6 or J62-7 and J27-6.
240 AC Voltage Low
Refer to the first paragraph for code 239 for explanation of what should happen when the input voltage is correct.
Voltage Low -- If the System Bias board determines AC voltage is too low it lights a red LED, D14, ACV LOW,
and sets the signal “AC V LOW b” on J62-10 to a “high”, about 24VDC (normal for a “low” here is 10-14VDC).
Power is not removed from T1 as low voltage won’t damage anything, However, if it’s too low for too long,
some things like contactors, AC solenoids, the gas controls or TSC 3000 may stop working. A low voltage, if it’s
low enough, may also light D3, the red Missing Phase LED. This does not indicate the phase is actually missing.
The voltage that triggers an AC Voltage Low fault is 380V for a 480VAC nominal line; 300V for a 380, 400 or
415VAC nominal line; 175V for a 208 or 230 VAC line.
Possible cause:
• Incoming voltage is now, or was previously, too low.
o Power distribution wires or power cord too small for the load.
o Loose or high resistance connection somewhere in the power distribution or power cord connection.
• Bad connection at J62 on the System Bias board or J27 on the CCM.
• Bad connection at J61 jumper on the System Bias board.
• System Bias board defective.
• CCM defective.
Troubleshooting:
1. If the fault is L240, applying START will clear the fault unless it becomes active again. An occasional problem
may be due to incoming voltage dips or sags (voltage drops lasting from ½ cycle to as much as a minute).
Usually, if the plasma is at fault, the problem will be present all the time. After ruling out everything else
we may have to attach a monitor to the power input to determine if this is the problem.
2. Voltage can be OK when not cutting or cutting at lower currents but at higher current too much voltage may
be lost due to undersize power cord or distribution wires.
a. Measure the voltage while cutting at higher current to determine if the drop is excessive.
b. Verify all power connections are clean and secure.
c. Verify correct wires size for the current draw per the recommendations in our manual as well as the local
electrical codes.
3. It is unlikely that an open connection on the J61 jumper would result in a 240 fault, it is more likely to cause
a Voltage Mismatch fault. However, if it’s intermittent at exactly the right time, perhaps not fully plugged
in, it possibly could show up as 240. Check the jumper at J61.