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VFC 3210
Bosch Rexroth AG
Electromagnetic Compatibility (EMC)
9.3.7 Ground Connections
Housing and Mounting Plate
By means of appropriate ground connections, it is possible to avoid the emis-
sion of interference, because interference is discharged to ground on the short-
est possible way.
Ground connections of the metal housings of EMC-critical components (such as
filters, devices of the frequency converter, connection points of the cable
shields, devices with microprocessor and switching power supply units) have to
be well contacted over a large surface area. This also applies to all screw con-
nections between mounting plate and control cabinet wall and to the mounting
of a ground bus to the mounting plate. The best solution is to use a zinc-coated
mounting plate. Compared to a lacquered plate, the connections in this area
have a good long-time stability.
Connection Elements
For lacquered mounting plates, always use screw connections with tooth lock
washers and zinc-coated, tinned screws as connection elements. At the connec-
tion points, remove the lacquer so that there is safe electric contact over a large
surface area. You achieve contact over a large surface area by means of bare
connection surfaces or several connection screws. For screw connections, you
can establish the contact to lacquered surfaces by using tooth lock washers.
Metal Surfaces
Always use connection elements (screws, nuts, plain washers) with good elec-
troconductive surface.
Bare zinc-coated or tinned metal surfaces have good electroconductive proper-
ties.
Anodized, yellow chromatized, black gunmetal finish or lacquered metal surfa-
ces have bad electroconductive properties.
Ground Wires and Shield Connections
For connecting ground wires and shield connections, it is not the cross section
but the size of contact surface that is important, as the high-frequency interfer-
ence current mainly flow on the surface of the conductor.
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DOK-RCON04-VFC3210****-IT01-EN-P
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