Specifications

19
Schneider Electric
Review (continued)
EMC phenomena
Disturbances and their effects
b Whether conducted or radiated, their presence generates common-mode currents
that flow in the equipment and cause malfunctions.
Solutions:
b Clamp conductors against ground planes to avoid the formation of ground loops.
b Make sure all exposed conductive parts have the same potential to limit the flow
of disturbing currents.
b Separate conductors by category to reduce the effects of crosstalk.
b Do not leave any conductors unconnected to prevent antenna effects.
The main EMC problems are conducted
common-mode disturbances.
Common-mode voltages are caused by:
b Antenna effect coupling.
b Common impedance coupling.
b Cable-to-cable coupling, for instance by
capacitive crosstalk (for electrical fields) or
inductive crosstalk (for magnetic fields).
E52285
Device 1
(isolated)
Device 2
(isolated)
Device 3
(grounded)
Differential
mode
voltage
Common
mode
voltage
Disturbed
cable
Common
mode
current
Stray
capacitance
Unshielded
cables
Shielded
cables
Cabling Guidelines