Digital Power Amplifier
Series VRD350 and VRD355
Installation Manual
7
IA VRD UK.INDD RH 02.06
Parker Hannifin GmbH & Co. KG
Hydraulic Controls Division
1.3. Connection
Connect unit in accordance with terminal connec-
tion diagram on page 9. The supply voltage for the
unit at terminals 26bd = 0V and 32bd = + U
B
is 18V
to 30VDC, residual ripple
≤
10%.
Output stages are electronically protected against
short circuit and excess current. The amplifiers
should be protected with a quick-acting preliminary
fuse (see technical data). Connection of solenoids
is made at teminals 22bdz and 28bdz for solenoid
A, terminals 24bdz and 30bdz for solenoid B. Ter-
minals bdz are bridged on the amplifier. Connection
should, however, be made to all three terminals on
account of the current carrying capacity.
If no electrical isolation of the logic inputs or outputs
is required, terminal 26bd must be bridged to termi-
nal 2d and terminal 32z to terminal 32bd.
General
Devices from the VRD350/VRD355 series are class
A equipment and thus only suitable for industrial
surroundings.
The distance between a source of interference
(device emitting interference) and an interference
sink (a device under the influence of interference)
is of decisive importance. The interfering field of the
source reduces the greater the distance between
this and the sink. In other words, the closer a device
is placed to a source of interference, the greater the
incidental amplitudes. For this reason, there should
be a minimum gap of 0.25 m between the amplifiers
and strong sources of interference.
The following devices are to be regarded as strong
sources of interference:
• Switching power supply units
• Frequency converters
• Drive modules
• Mains filters with wiring (even if screened)
• AC/DC commutator motors
• Motor cables (even if screened)
• Switched inductances, even when anti-inter-
ference measures have been taken (solenoid
valves, contactors, relays, brakes, etc.)
One of the most common input points is the wiring.
This influence can be minimised. Interfering cables
should therefore be laid at least 0.25m away from
cables susceptible to interference. Parts of the
amplifier wiring may be susceptible to interference
(command signal, actual value, solenoid cables,
etc.). Parallel laying of cables is very critical. The
necessary distance has to be increased if cables
are laid parallel over longer distances (> 10 m).
The influence is least when cables cross, particu-
larly if this is at an angle of 90°. Nor should cables
susceptible to interference ever be laid parallel to
motor cables, in particular over longer distances,
and must always cross these at an angle of 90°.
However, interference can also arise from cables in
the amplifier wiring system, in particular solenoid
cables.
Examples of devices which are particularly sus-
ceptible to interferences:
• Office PC’s
• Sensors with small output voltages
• Proximity switches (capacitive)
• Audio equipment (TV, Hi-Fi, radio, etc.)
• Devices which do not comply with EMC guide-
lines.
The assembly contains electronic
components. Incorrect handling or
operation can lead to damage through
electrostatic discharge (ESD). Only
trained personnel should work with the unit. All
safety instructions must be observed. If the card is
disconnected whilst the power supply is still dam-
age may result. Avoid such actions at all cost.
