Tweco 400 Ultra-Cut XT Plasma Cutting System - Manual (Page 214)

ULTRA-CUT 100 XT/200 XT/300 XT/400 XT
A-80 APPENDIX Manual 0-5297
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.
4. If the incoming voltage is OK and the problem persists it may be System Bias, CCM or connection between
J62 and J27.
a. If the incoming voltage is OK and D14, ACV LOW, is on or the signal “AC V LOW b” on J62-10 is “high”
(about 24VDC, relative to TP1 or J62-8 ) the System Bias board is defective.
b. If D14 is not on and signal “AC V HIGH b” on J62-10 is “low” (about 10-14VDC, relative to TP1 or J62-8)
then System Bias is OK and problem is in the CCM.
c. If J62-10 is near zero volts there may be a bad connection between J62-10 and J27-10 or J62-7 and J27-7.
241-246 Inverter Section Input Voltage Error.
The System Bias board checks for input voltage high, low or missing a phase from the power coming in from the
power cord. It is unlikely but not impossible that a problem with the incoming power could result in 241-246
codes. The 241-246 codes more likely point to problems with the power into or within a single inverter section
or in the case of missing phase it may be the contactor that supplies up to 3 inverter sections.
Once the input contactors close, applying voltage to the inverters, they test for input too high or too low and for
missing phase. When the input voltage is in the correct range, a green LED, D4, named READY, lights on the left
side of the main inverter board. If D4 is not on, either the input voltage is out of range or the inverter is defective.
You can still get the 241-246 code with a missing phase with the READY LED on. The LED will be going on and
off rapidly but appears to the eye to be on. In this case you can measure the signal on the ribbon cable. The
signal previously called READY is now called AC_INPUT_FLT. It is a differential signal on pins 1(+) & 2(-) of
the inverters 30 pin ribbon cable. If the AC input is correct you should read 5-6V between the pins. If AC_IN-
PUT_FLT is true voltage on pins 1 & 2 will be less than 2V.
Some of the other faults such as Inverter Fault and Over Temperature also set the AC_INPUT_FLT (not Ready).
However, they will latch on associated LEDs or set different fault codes. In the event of an Input Voltage Fault
the CCM does not remove power from the inverter.
Things that can cause Input Voltage Fault codes:
1. Intermittently having the power drop out on one or more phases for at least 1 ms. a longer term loss would
more likely trigger a different fault. If it’s the incoming power it would be likely not always be the same
inverter.
2. Phase missing or intermittent to a specific inverter the fault would always call out that inverter.
3. Intermittent connections on the fault signal internal to the inverter.
247-252 Inverter Fault
Once the input contactors close applying voltage to the inverters several tests are performed. The Inverter Fault
signal latches on so even if the cause has gone away you can see that there was a fault as indicated by red LED
D1, INV FLT on the inverter Control & Fault PCB. It is reset by applying start signal or cycling power. If the
fault is still present it will come back on.
Things that cause an inverter fault: