Electro-Magnetic Interference (EMI) Issues
4
Important note:
A built-in RC noise
suppression circuit may
be connected in parallel
with relay contacts.
Full AC voltage isolation
may NOT be provided
when relay contacts
are open.
Small AC current
(≈ 1.5 mA at 230 VAC)
may still flow through
the RC circuit!
♦ All signal wires must be shielded.
They must not be packaged together
with power cables!
♦ Never lay the signal wires close
to inductive or capacitive noise
sources, such as relays, contactors,
motors, etc.!
♦ All shields have to be grounded ONLY
at one end, as closer as possible
to the controller terminals!
♦ Avoid sharing supply lines
with powerful consumers,
especially with inductive loads,
switched on and off.
♦ To stop unwelcome interference
signals entering through the power
supply lines, use shielded 1:1
isolation transformer!
♦ Shunt all switched (not only those
switched by the controller) inductive
consumers with special suppression
networks: RC group and varistor -
for AC loads, or diode - for DC loads.
♦ If the controller operates in a very
powerful EMI area, it has to be
mounted inside a grounded metal
shielding box!
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