Cable - Mitsubishi Electric MELCEC Q Series User Manual

8. EMC AND LOW VOLTAGE DIRECTIVES
8.1.3

Cable

The cables extracted from the control panel contain a high frequency noise component.
On the outside of the control panel, therefore, they serve as antennas to emit noise. To
prevent noise emission, use shielded cables for the cables which are connected to the I/O
modules and intelligent function modules and may be extracted to the outside of the
control panel.
The use of a shielded cable also increases noise resistance.
The signal lines (including common line) of the programmable controller, which are
connected to I/O modules, intelligent function modules and/or extension cables, have
noise durability in the condition of grounding their shields by using the shielded cables. If a
shielded cable is not used or not grounded correctly, the noise resistance will not meet the
specified requirements.
(1) Grounding of shielded cables
(a) Ground the shield of the shielded cable as near the module as possible so that
the grounded cables are not induced electromagnetically by the cable to be
grounded.
(b) Partly remove the outer sheath of the shielded cable so that it can be contacted
with the widest possible area of the control panel. A clamp may also be used as
shown in the figure below. In this case, cover the control panel's inner surface
which will come in contact with the clamp when painting.
Note) Grounding a shield cable by soldering a wire to the shield section as
illustrated below is not recommended. The high frequency impedance
will increase and the shield will be ineffective.
8 - 4