
A-72937EN/11
To meet the requirement of the EMC Directive
TMN06007E_A-72937EN_11.DOC
- 9 -
3.1.6 Eliminate conductive stuffs floating electrically
As described earlier in this chapter, be sure to ground conductive stuffs that
are floating electrically in a cabinet. Those floating stuffs are easily
influenced by electric wave and they immediately act as antenna. Metal
fittings prepared for mounting of units and shield cables used because of
availability of materials although they need not to be tend to be overlooked.
Pay attention to those stuffs especially.
3.1.7 Operation box
Pay attention to the following points in designing an operation box where an
operator’s panel like CRT/MDI is installed.
①
A faceplate of operator’s panel should have paint removed at flange
portion so that the faceplate has electric contact toward the operation
box. Of course the operation box needs to have same construction, that
is, paint must be removed around the
mounting hole. For mounting, use conductive gasket.
②
When the box has a door, use a conductive gasket between the box and
the door and make sure to have tight electric contact in between when
the door is closed. This is the same consideration as a main cabinet.
③
As described in Chapter 4, shield of video signal cable needs to be
grounded at the operator’s panel side as well. Therefore, the operation
box should have cable- clamping system in it. (See section 4.1)
④
Tie the cabinet and the box by a thick ground wire, unless those two are
connected tightly through a machine body or a part of the main cabinet.
3.1.8 Separation of input power portion
In a magnetics cabinet, there are units that emit noise and the cabinet is, so
to speak, filled with electric wave. Therefore, cables come out of a cabinet are
influenced by them directly and/or indirectly and the cables are just like
antenna to emit electric wave. If those cables come out without any
countermeasure, they emit big noise and a system does not get the test
passed. This section describes about the input power portion of the cabinet.
Cables are described in chapter 4 in detail.
As it is easily understood, a problem we are going to solve in this section is
the noise emitted by power input cable going out of a cabinet. As it is difficult
to take countermeasure like shielding in power input cables, we separate the
input power portion from other portion of a cabinet so that the input power
cable is not contaminated by noise inside the cabinet. See the drawing below.