9. EMC DIRECTIVE AND LOW-VOLTAGE INSTRUCTION
9 - 4
MELSEC-
(1) Shield earthing
When a shield of the shielded cable is earthed to the cabinet body, please ensure
that the shield contact with the body is over a large surface area. If the cabinet
body is painted it will be necessary to remove paint from the contact area. All
fastenings must be metallic and the shield and earthing contact must be made
over the largest available surface area. If the contact surfaces are too uneven for
optimal contact to be made either use washers to correct for surface
inconsistencies or use an abrasive to level the surfaces. The following diagrams
show examples of how to provide good surface contact of shield earthing by use
of a cable clamp.
Shield section
(a) Peal the cable insulation off
and expose the shield section.
Screw
Shielded cable
Paint mask
Clamp fitting
(b) Sandwich the exposed shield section with the
and earth to the control cabinet over a wide area.
Note) The method of earthing by soldering a wire onto the shield section of the
shielded cable as shown below is not recommended. The high frequency
impedance will increase and the shield will be ineffective.
Shielded cable
Wire
Crimp terminal
(2) MELSECNET/II, MELSECNET/10 module
(a) The following requirements apply to A1SJ71AR21, A1SJ71BR11,
AnNCPUR21, AnACPUR21.
Always use a triaxial cable for the module. The radiated noise in the
band of 30 M Hz or higher can be suppressed by using a triax cable.
Earth the outer shield by the method described in (1).
Earth this section
(b) Always mount a ferrite core onto the triaxial cable. Mount the ferrite core
near the control cabinet outlet of each cable. Use of the TDK ZCAT3035
ferrite core is recommended.
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