Tweco Troubleshooting Power Supply - Manual (Page 8)

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charges a capacitor. If using a meter with a diode scale, expect to see
continuity one way (diode forward biased) and open with probes reversed.
A low resistance with either method indicates a short.
• Chopper IGBTs. Measure resistance TB1 to TB4 on chopper. Should be
open circuit. . If using a meter with a diode scale expect to see continuity
one way (diode forward biased) and open with probes reversed. A low
resistance with either method indicates a short.
1-3
Pilot Out
Pilot has ignited as sensed by Pilot On signal, but went out on its own before the
timeout (85 ms. or 3 sec.).
Possible causes:
• Preflow pressure too high, check cut charts for proper setting.
• Cutting current set too low for the torch parts being used. Pilot current
level is automatically set based on the cutting current. A low cutting
current results in a lower pilot current that may not be able to sustain a
pilot for higher current torch parts.
• Remote Analog Current Control switches set wrong can also result in
lower than normal pilot current setting. See section on these switch
settings under next section for code 1-4.
• Pilot Regulator (Chopper) Defective, refer to previous section 1-2 for
quick test to see if chopper is defective.
• Defective Inverter module. The inverter modules supply the power for the
pilot while the pilot regulator (chopper) regulates its current. For power
supplies with 2 or 3 inverters (150A, 200A or 300A), each inverter
supplies a portion of that power. If one inverter is not working it may be
enough to start a pilot but not to maintain it thus code 1-3, pilot out early.
o To determine if one inverter is not working, first disconnect the
arcstarter cable so the pilot won’t try to start and there will be no
HF.
o Disconnect the 16 circuit ribbon cable from all but one of the
inverters (CN6 on inverter PCB13). Prepare to measure DCV
approximately 300-400VDC between the torch (-) busbar
connection and the Work (+) busbar.
o Apply CNC Start, voltage should immediately be present and stay
on for about 15 seconds. After 15 seconds you will get a 1-2 code
but that is normal because with no HF the pilot can’t ignite. If
voltage is present repeat the test with each of the other inverters.
Any inverter that the voltage doesn’t appear is defective.
1-4
Loss of Transfer
Arc transferred to metal for at least 50 ms. then went out.