ELECTROMAGNETIC COMPATIBILITY (EMC)
ii
Hypertherm
4-08
Earthing of workpiece
Where the workpiece is not bonded to earth for electrical
safety, nor connected to earth because of its size and
position, for ex am ple, ship’s hull or building steel work, a
con nec tion bonding the work piece to earth may reduce
emis sions in some, but not all instances. Care should be
taken to prevent the earthing of the work piece in creas ing
the risk of injury to users, or damage to other elec tri cal
equip ment. Where necessary, the con nec tion of the
workpiece to earth should be made by a direct
connection to the workpiece, but in some countries where
direct connection is not permitted, the bonding should be
achieved by suitable capacitances se lect ed according to
national regulations.
Note: the cutting circuit may or may not be earthed for
safety reasons. Changing the earthing arrangements
should only be au tho rized by a person who is competent
to assess whether the chang es will in crease the risk of
injury, for example, by al low ing parallel cutting cur rent
return paths which may damage the earth cir cuits of other
equipment. Further guid ance is given in IEC/TS 62081
Arc Welding Equip ment Installation and Use.
Screening and shielding
Selective screening and shielding of other cables
and equipment in the surrounding area may alleviate
problems of in ter fer ence. Screening of the entire
plasma cutting installation may be con sid ered for
special applications.
