Tweco Troubleshooting Power Supply - Manual (Page 28)

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defective. Signal Inverter OCR is sent to CCM on J36-16. If CN6-12 is not low
and J36-16 is low PCB5 is defective or the 34 ckt ribbon cable is shorted.
CCM
If J35-16 is not low but code 2-6 is still flashing then CCM is defective.
2-7 Unwanted Current
As soon as CNC Start is on, the inverters are turned on and should be
producing open circuit voltage (OCV). There should be no output current at this
time because without pilot ignition there should be no path for current.
Power supply monitors for current using current sensors HCT1 on the output
of the chopper module (or on the pilot buss bar for early resistor pilot units) and
HCT2 on the Work buss bar. System performs 3 tests for unwanted current. Two
are for current on either the pilot circuit (sets code 2-8) or Work cable (sets code
2-9) as indicated by digital signals Pilot ON and Arc Transferred.
The third test uses the analog output (sum of the two current sensors) and if
analog signal indicates over 20A set code 2-7. CCM software prior to version 2.1
looks at the analog signal first (2-7) then the pilot and work digital signals (2-8 &
2-9). Result of this is most unwanted currents faults will set 2-7 which doesn’t
indicate if fault is in pilot or work. Starting with software version 2.1 we switched
the order so the digital signals (codes 2-8 & 2-9) are looked at first followed by
the analog signal. In most cases this should isolate the fault quicker.
After version 2.1 any faults that set 2-7 should be limited to defective PCBs.
Actual shorts should set codes 2-8 or 2-9.
Code 2-7 If current over about 20A is detected during preflow, before pilot
ignition, CCM blocks ignition, shuts off the inverters, turns off the pilot contactor
and chopper, and sets code 2-7. Code is latched so you can determine what
caused shutdown after Start is removed. Code is reset next time CNC Start is
applied (assuming fault is corrected).
Causes for code 2-7 (Software prior to version 2.1):
• Short between power supply negative output (TORCH terminal on back of
power supply) and pilot circuit.
• Short between power supply negative output and Work circuit.
• Short between power supply negative output and earth ground.
• Defective of incorrectly installed user supplied equipment such as torch
height controls that make connections to power supply output.
• Defective pilot or work current sensors.
• Defective PCB5
• Defective CCM
•
Causes for code 2-7 (Software version 2.1 and later):
• Defective PCB5
• Defective CCM