8
IA VRD UK.INDD RH 02.06
Digital Power Amplifier
Series VRD350 and VRD355
Installation Manual
Parker Hannifin GmbH & Co. KG
Hydraulic Controls Division
Special Notes on Wwiring and Electrical Cabi-
net Design
The following rules and tips by no means claim to
be complete. Since various electronic components
are used in a variety of different ambient conditions,
these guidelines only represent a compromise. The
actual design of the wiring also depends on the
interference emission and resistance to jamming
of the individual components.
• Use screened and twisted pairs of cables for
the solenoid connections. The screen must be
earthed (PE) at both ends. The capacity should
be 120pF/m. Cables must be
≥
1.5mm² for a
length up to 100m and
≥
2.5mm² for a length
over 100m.
• Digital signal lines are to be connected at both
ends to PE with a good conductivity. Command
signal and actual value connections should have
screened and twisted cables. These analog
signal lines are to be connected to earth at
both ends with a good potential equalisation.
The screen connections should be made over
a large area.
• In environments with great interference, use
doublescreened cables for command signal
and actual value connections. The inner screen
is only earthed at one end, the outer screen at
both ends.
• In the event of low-frequency interferences
on the analog signal lines (measured value
fluctuations), the screen should be connected
at one end. However, a corresponding potential
equalisation is preferred. (See also following
point)
• The reference point for command signal and
actual value signals is analog 0V (terminal 26z).
All setpoint and actual value transmitters are to
be connected to this terminal so as to avoid zero
shifts and incorrect measurements.
• When replacing older devices, the non-fused
earthed conductor (PE) should be connected
to terminal 18d or 18b. If ripple voltages oc-
cur, connect 16b or 20b to PE. In this case the
connection to 18bd must be removed. (But:
preferably make a potential equalisation!)
• Use only cables with a Cu screening grid and
a covering of > 85% whenever possible. Avoid
screening films.
• The screen may not be interrupted along the
entire length of the cable. If contactors, safety
switches, chokes, etc. have to be used in the
wiring, the installation of a metallic housing with
a high HF attenuation may be necessary.
• Screen terminals are to be connected over a
large area to the screen rail.
• The screen rail is to be installed close to the
cable duct in the electrical cabinet.
• The metallic parts of the electrical cabinet
are to be connected with high conductivity on
large areas. Avoid painted surfaces. Make the
desired connection with mechanical aids such
as scratch plates if necessary. The doors are
to be connected to the cabinet via the shortest
possible homogeneous tapes (multiple).
• Solenoid valves, contactors, relays, brakes, etc.,
are to be suppressed directly at the respective
coil. Suitable suppression devices are, for ex-
ample, RC networks, diodes or varistors.
• Analog and digital signal lines should preferably
enter the electrical cabinet from one side.
• Unscreened lines of an electric circuit are to be
twisted.
• Auxiliary wires are to be earthed at both ends.
• Avoid unnecessarily long lines. This keeps the
coupling inductances and capacities small.
• Wiring should preferably not be free in the cabi-
net. Cables, including auxiliary cables, should
be laid as close as possible to mounting plates
and the cabinet housing.
• In the event of an inadequate potential equalisa-
tion between the screen connections, a balanc-
ing conductor
>
10 mm² should be laid parallel
to the screen to reduce the screen current. A
multiple connection of the screen to the cabinet
casing and thus PE is generally possible. A mul-
tiple connection of the screen is also permissible
outside the cabinet.
• If filters are fitted, these should be installed
close to the source of interference and with a
good surface contact on the cabinet or mounting
plate.
• If converters are used, converter filters must be
provided. Variable speed motors may have to be
connected using screened lines.
• All further instructions of the converter manu-
facturer are to be observed.
