Hypertherm HT4001 Plasma Arc Cutting System User Manual
Page 257
APPENDIX F – SYSTEM GROUNDING
f-2
HT4001
Instruction Manual
purchased locally, using a minimum 8 AWG UL Type MTW cable (USA specification) or the appropriate cable
specified by national and local codes.
Consult the appropriate manufacturer’s instructions to ground equipment that does not receive power from the
power supply.
Work Table Grounding
If a supplementary ground rod is installed near the worktable to reduce EMI, it must be connected directly to
the PE ground of the building structure, connected to the service ground; or to earth, providing the resistance
between the ground rod and the service ground meets national or local codes. Place the supplementary
ground rod within 20 ft (6 m) of the worktable according to national or local codes.
If any module is grounded to the work table, the work table must be grounded to the power supply, or the
configuration must be changed to comply with applicable national and local electrical codes.
A ferrite choke can be placed in the conductor between the work table ground rod and the PE ground, with a
number of turns through the choke to isolate the safety ground (at 60 Hz) from any electromagnetic
interference (frequencies above 150 Khz). The more turns the better. A suitable ferrite choke can be made by
wrapping 10 turns or more of the ground lead through Magnetics part number 77109-A7, Fair-Rite part
number 59-77011101, or other equivalent ferrite choke. Locate the choke as close as possible to the plasma
power supply.