CE Conformity, Directives and Standards KeTop T50VGA
156 User's Manual, Version: 1.3
© KEBA 2007
Ferrites
Ferrites operating via data lines work in a similar way to current-
compensating chokes. The wanted signals (see illustration) can pass un-
hindered and the interference signals are damped. A fundamental differ-
ence from current-compensating chokes is that in the case of ferrites the
application range takes place at higher frequencies and therefore the mate-
rial losses are responsible for the damping and the interference is not re-
flected, as in the case of inductance, but is converted into heat.
Ferrite
I
O
I
O
I
I
I
I
Data lines
I
I
... Interference current
I
O
... Operating current
Current flow for ferrites
14.3.2.3 Prevention of couplings
Coupling between interference sensitive signals (e.g. analogue signals) and
the lines that carry the interference signals (e.g. motor lines) can be re-
duced by laying cables separately.
14.3.3 EMC measures on KeTop
The KeTop is designed for industrial applications. Considerable electro-
magnetic and electrostatic interference can occur in this environment. For
this reason special emphasis was placed on interference immunity and
data security in the design of the device. The EMC design implemented
and described below considers all the above named sources of interference
and the possible coupling paths.
z All shielding and filter measures (filtered power supply) in the KeTop
are carried out directly on the printed circuit board.
z The special design of the KeTop cable guarantees interference immu-
nity even for greater connection lengths, i.e. the data lines (communica-
tion signals) are shielded and so they are separated from the control
lines (power supply, enabling button, emergency off, key-operated
switch etc.) inside the KeTop cable.
z Power supply lines in the control cabinet are usually unshielded. They
are therefore laid outside the KeTop cable shield in order to prevent a
coupling with the sensitive data lines.
z The unshielded control and power supply lines are either filtered on en-
try into the shielded housing of the KeTop or separated from the elec-
tronics in such a way that any interference signals carried by these lines
cannot affect the internal electronics of the KeTop.
z It is not necessary to lay the KeTop cable separately.
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