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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 happens 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 information.

- 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.

4 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.

1) EMISSIONS. Three ways can be followed to reduce the emissions:

- SOURCE OF EMISSIONS: finding the main source of disturb and work

on it.

- SHIELDING: enclosing contactor and controller in a shielded box; using

shielded cables;

- 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.

2) ELECTROMAGNETIC IMMUNITY. The considerations made for emissions

are valid also for immunity. Additionally, further protection can be achieved

with ferrite beads and bypass capacitors.

3) ELECTROSTATIC IMMUNITY. Three ways can be followed to prevent

damages from ESD:

- 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.

- ISOLATION: use anti-static containers when transferring ESD-sensitive

material.

- 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 is strongly suggested to connect to truck frame all the parts

of the truck which can be touched by the operator, who is most of the

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Zapi AC-2 User Manual Page 18

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