4.2.2 EMC-equitable assembly
Mostly, measures for suppressing interference voltages are only taken, when the control
is already in commission and the perfect receive of a wanted signal is disturbed. Causes
for such interference's are in the most cases inadequate reference potentials, coming
from mistakes at the device assembly and installation.
When assembling the devices, you have to ensure the large-surface grounding of the
inactive metal parts. A correctly done grounding supports an unambiguous reference
potential for the control and reduces the impact of coupled interferences.
Grounding means the conducting connection of all inactive metal parts. The sum of all
interconnected inactive parts is called ground.
Inactive parts are all conductive parts electrically separated from all active parts by
means of a basic isolation and that may only get voltage in case of an error.
The ground must not adopt dangerous contact voltage even in case of an error. Thus you
have to connect the ground with the protected earth conductor. To avoid ground loops,
local distant ground constructions (cubicles, construction and machine parts) have to be
connected with the protected earth conductor system in star-topology.
Please regard at grounding:
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Connect the inactive metal parts as carefully as the active ones.
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Take care of impedance-low metal-metal-connections, e.g. with large-surface and well
conductive contacts.
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If you include coated or anodized metal parts in the grounding, you have to come
through the isolating protection layers. For this you may use special contact washers
or remove the isolation layer.
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Protect the connection points from corrosion, e.g. with grease.
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Moveable grounding parts (e.g. cubicle doors) have to be connected via flexible
ground strips. The ground strips should be short and have a large surface, because
the surface is decisive for the diversion of high frequency interferences.
Guidelines for assembling
and grounding of inactive
metal parts
HMI
Industrial Security and Installation guidelines
Installation guidelines > EMC-equitable assembly
HB160 | TP-smart | H71-71A41-0 | en | 23-10
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