Tweco Troubleshooting Power Supply - Manual (Page 29)

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For troubleshooting code 2-7 with software prior to version 2.1 got to Troubleshooting
Unwanted Current Faults and start the beginning.
For troubleshooting code 2-7 with software version 2.1 or later got to Troubleshooting
Unwanted Current Faults sections on PCB5 and CCM.
2-8 Unwanted Pilot Current Signal
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). If any
current (more than about 5A) is detected during preflow, before pilot ignition,
CCM blocks ignition, shuts off the inverters, turns off the pilot contactor and
chopper, and sets code 2-8. 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 2-8:
• Short between electrode and tip due to mismatch of consumables or
foreign matter between tip and electrode.
• Shorted torch body.
• Short between power supply negative output (TORCH terminal on back of
power supply) and pilot circuit..
• Defective of incorrectly installed user supplied equipment such as torch
height controls that make connections to power supply output.
• Defective pilot current sensor.
• Defective PCB5
• Defective CCM
Refer to section: Troubleshooting Unwanted Current Faults (codes 2-7, 2-8, 2-9)
following section 2-9 to troubleshoot.
2-9
Unwanted Transfer Signal
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 work lead current using current sensor HCT2 on the Work
buss bar. If any current is detected during preflow, before pilot ignition, CCM
blocks ignition, shuts off the inverters, turns off the pilot contactor and chopper,
and sets code 2-8. 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).
• Short between power supply negative output and Work circuit.