Reliability, Safety
E 811 GB
10
27/02/2013
2.6.4 Electrical Immission Safeguard
To eliminate electromagnetic interference, connect the control system to the
protective earth conductor. Practice best cable routing.
2.6.5 Cable Routing and Wiring
Keep power circuits separate from control circuits:
•
DC voltages
60 V ... 400 V
•
AC voltages
25 V ... 400 V
Joint laying of control circuits is allowed for:
•
shielded data signals
•
shielded analogue signals
•
unshielded digital I/O lines
•
unshielded DC voltages < 60 V
•
unshielded AC voltages < 25 V
2.6.6 Location of Installation
Ensure that temperatures, contaminations, impact, vibration or electromag-
netic interference are no impediment to the installation.
2.6.6.1 Temperature
Consider heat sources such as general heating of rooms, sunlight, heat ac-
cumulation in assembly rooms or control cabinets.
2.6.6.2 Contamination
Use suitable casings to avoid possible negative influences due to humidity,
corrosive gas, liquid or conducting dust.
2.6.6.3 Impact and Vibration
Consider possible influences caused by motors, compressors, transfer lines,
presses, ramming machines and vehicles.
2.6.6.4 Electromagnetic Interference
Consider electromagnetic interference from various local sources: motors,
switching devices, switching thyristors, radio-controlled devices, welding
equipment, arcing, switched-mode power supplies, converters / inverters.
2.6.7 Particular Sources of Interference
2.6.7.1 Inductive Actuators
Switching off inductances (such as from relays, contactors, solenoids or
switching magnets) produces surge voltages. It is necessary to reduce these
extra voltages to a minimum.
Throttling elements could be diodes, Z-diodes, varistors or RC elements.
Their rating should conform to the specifications provided by the manufac-
turer or supplier of the actuators.
