Weidmüller 1334950000, Manual

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7 Earthing and shielding | Earthing of shielded cables
49 Manual u-control 2604080000/03/08.2020
In practice, the shield is still often twisted and connected
to a terminal point. There is very high attenuation (voltage
drop) on these connections, especially for high-frequency
interference. Therefore, this type of shielding should not
be used, even for short cable lengths. The shielding of the
cable is practically negated and can, at best, be helpful for
low-frequency interference. We recommend that there is a
large amount of surface contact with the braided shield of
the cable.
There are generally four distinct types of coupling:
– Galvanic coupling
– Capacitive coupling
– Inductive coupling
– Radiation coupling
These types of interference usually occur mixed together, but
they can be categorised as follows:
– Electromagnetic fields
– Ripple voltage (50 Hz)
– Lightning
– Interference pulses (current, voltage)
– Transient surge voltages
– Radio interference
– ESD (electrostatic discharge)
– Burst
– Mains feedback
Another area of concern as regards shield
contact is the “flow” within the conductor. Tem -
perature changes caused by the current lead
to changes in the conductor cross-section. A
rigid contact can therefore only be partially
effective. A self-adjusting contact is what is
really required. Weidmüller's clamping bracket
products (KLBÜ series) provide the perfect
solution to meet this challenge.
Use of a clamping bracket