Cables - Mitsubishi MELESEC-ST User Manual

11 EMC AND LOW VOLTAGE DIRECTIVE

11.1.3 Cables

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(d) Ferrite cores should be attached to all power wire at the wire hole of the
control box.
External
SYS. power
supply
Ferrite cores
100VAC
If cables are pulled out from the control panel, they will wear noise of high frequency
and emit the noise outside the control panel by functioning as an antenna.
The shielded cables should be used for the case that cables used for connecting to I/O
modules or intelligent function modules will be pulled out from the control panel.
The use of shielded cables increases noise immunity.
The noise immunity of signal lines for MELSEC-ST series I/O modules and intelligent
function modules is ensured under the conditions where shielded cables are used and
the shield is grounded. If shielded cables are not used or the shield is not correctly
grounded, the noise immunity will not meet the requirements specified by the standard.
(1) Grounding shield of shielded cable
(a) Ground the shield of shielded cables as near as possible to the module,
taking care so that the grounded cables will not be inducted
electromagnetically by the ones not grounded yet.
(b) Strip the outer insulation layer of the shielded cable to expose a part of
braided shield as shown below. Then, ground the shielded section, i.e.,
exposed part of braided shield, in the largest area as possible to the control
panel. A clamp fitting may be used as shown in the figure below. In this
case, remove the coating from the inside of the control box, which will come
in contact with the clamp fitting.
Shield section
Bush refreshing module Control box
External
AUX. power
supply
100VAC
Paint mask
MELSEC-ST
Screw
Clamp fitting
Shielded cable
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