Hypertherm HT4400 HySpeed Plasma Arc Cutting System - Manual (Page 121)

MAINTENANCE
5-30 HT4400 Instruction Manual
3
Chopper
Plasma Power Supply
Start Circuit
Choke
Control
Logic
IGBT
Power Resistor
ALEL Caps
Diode
Cutting Cutting
Arc
Pilot Pilot
Arc
Start Circuit Functional Schematic
Start Circuit Troubleshooting
• D2 should always be ON.
• D1 illuminates as soon as the torch fires and then will extinguish as soon as the arc transfers to the plate. If
arc transfer is immediate, the LED will not illuminate.
• If there is no arc at the torch or if the arc will not transfer:
• Turn the power to the system OFF and check for a resistance of 15 k Ω from H8 to H1.
• Check for a resistance of 5.5 k
Ω
across H10 and H4.
• Refer to wiring diagrams. Note that the resistances will slowly increase to the above values due to
capacitance in the circuit.
• Check the junction of the D12 diode.
• Work cable connection on the cutting table is not making good contact.
• Check D2. It should be illuminated.
• Fire the torch in the air and check to be sure that D1 illuminates.
• Check the resistance across the R3 resistor. It should be 10 k
Ω .
WARNING
SHOCK HAZARD: Always use caution when servicing a power supply when plugged in and the
covers are removed. Dangerous voltages exist within the power supply which could cause injury
or death.