Zapi ACEX, User Manual

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Page - 20/81 AFCZP0BC- COMBIACX & ACEX - User Manual
simulate external undesired disturbances and verify the electronic devices
response.
3) The second type of immunity,
ESD
, concerns the prevention of the effects of
electric current due to excessive electric charge stored in an object. In fact,
when a charge is created on a material and it remains there, it becomes an
“electrostatic charge”; ESD happen when there is a rapid transfer from a
charged object to another. This rapid transfer has, in turn, two important effects:
-
this rapid charge transfer can determine, by induction, disturbs on the signal
wiring and thus create malfunctions; this effect is particularly critical in
modern machines, with serial communications (canbus) which are spread
everywhere on the truck and which carry critical informations.
- in the worst case and when the amount of charge is very high, the discharge
process can determine failures in the electronic devices; the type of failure
can vary from an intermittently malfunction to a completely failure of the
electronic device.
U
IMPORTANT NOTE: it is always much easier and cheaper to avoid ESD from
being generated, than to increase the level of immunity of the electronic
devices.
There are different solutions for EMC issues, depending on level of emissions/
immunity required, the type of controller, materials and position of the wires and
electronic components.
4)
EMISSIONS
. Three ways can be followed to reduce the emissions:
A) SOURCE OF EMISSIONS: finding the main source of disturb and work on
it.
B) SHIELDING: enclosing contactor and controller in a shielded box; using
shielded cables;
C) LAYOUT: a good layout of the cables can minimize the antenna effect;
cables running nearby the truck frame or in iron channels connected to truck
frames is generally a suggested not expensive solution to reduce the
emission level.
5)
ELECTROMAGNETIC IMMUNITY
. The considerations made for emissions are
valid also for immunity. Additionally, further protection can be achieved with
ferrite beads and bypass capacitors.
6)
ELECTROSTATIC IMMUNITY
. Three ways can be followed to prevent
damages from ESD:
A) PREVENTION: when handling ESD-sensitive electronic parts, ensure the
operator is grounded; test grounding devices on a daily basis for correct
functioning; this precaution is particularly important during controller
handling in the storing and installation phase.
B) ISOLATION: use anti-static containers when transferring ESD-sensitive
material.
C) GROUNDING: when a complete isolation cannot be achieved, a good
grounding can divert the discharge current trough a “safe” path; the frame of
a truck can works like a “local earth ground”, absorbing excess charge.
So it