12
Parker Hannifin Manufacturing Germany GmbH & Co. KG
Pump & Motor Division Europe
Chemnitz, Germany
Electro hydraulic proportional controls version 45 for
axial piston pumps, PV series
Bulletin MSG30-3254-INST/UK
Installation and setup manual
6. External pilot pressure supply
The alternative solution is, to supply the control
circuit from an external auxiliary pilot pressure
supply circuit. The servo system is discon-
nected from the pump outlet (plug inside of the
pump gage port). The pump outlet pressure is
connected via a check valve to the pilot pres-
sure port.
An external source for auxiliary power (capable
of a flow of 20 – 40 l/min (depending on pump
size) at a pressure of 20 – 30 bar) is also con-
nected via a check valve to the pilot port.
Figure 10 shows the hydraulic circuit for this
option.
As long as the pump outlet pressure is lower,
than the external supply pressure, the control
circuit is powered by the external source.
When the system pressure exceeds the auxiliary
pressure, the control is internally pressurized.
Please note:
- for pressures below the auxiliary pressure a
pressure control is not possible, because the
control senses the supply pressure.
- using this option the pump can be operated at
0 bar and dead head. Under these conditions
the pump does not provide drain flow and the
pump can overheat. Case flushing is necessary.
I
Q:A
I
P
X
P
X
Q
S
T
T
U s
T
T
T
WV
M
p1
W
Q
W
P
A
A
A M
M
B
D2
B
p
P
P
P
P
P
check valves
X
Q
= signal, displacement
I
Q:A
= solenoid current A, displacement control valve
X
P
= signal, pressure sensor
I
P
= solenoid current, pressure pilot valve
W
Q
= command, displacement
W
P
= command, pressure
Figure 10:
Hydraulic circuit of a pump with external pilot pressure supply