Limitation; Pvpx, Electrical Ls Unloading Valve - Danfoss PVG 32 Technical Information

Technical Information
PVG 32 Proportional Valve Group
Function

PVPX, electrical LS unloading valve

24 | © Danfoss | August 2017
pressure limitation can be used. It will appear from the characteristics enclosed what effect a pressure
limitation, P will have on max. flow on the lowering port.
LS
The size for a "full" pressure control spool is determined on basis of known load pressure, P
requested max. flow.
It will appear from the characteristics enclosed that if the load PLS is low and the pump pressure, P
high as a result of max. stroked spool you will get a large flow.
If P is approaching PLS max. the flow will be reduced and the dead band increased. Max. oil flow can be
LS
reduced by approx. 50% without limiting max. pressure.
The reduction is made by limiting the spool travel from 7 mm to 5.5 mm.

Limitation

If a pressure controlled spool is chosen for stability reasons consideration should be made to features
related to the pressure control principle.
Deadband will change according to the load conditions and the valve section will become load-
dependent and that the pump pressure may exceed the load pressure.
With all of the above in mind, a "pressure controlled spool" will minimize oscillation and obtain a stable
function that can be controlled smooth and precise.
PVPX is a solenoid LS unloading valve. PVPX is fitted into the pump side module enabling a connection to
be made between the LS and the tank lines. Thus the LS signal can be relieved to tank by means of an
electric signal.
For a PVP pump side module in open center version the relief to tank of the LS signal means that the
pressure in the system is reduced to the sum of the tank port pressure plus the neutral flow pressure for
the pump side module.
For a PVP pump side module in closed center version the relief to tank of the LS signal means that the
pressure is reduced to the sum of the tank port pressure for the pump side module plus the stand-by
pressure of the pump.
PVPX, electrical LS unloading valve
T
LS
P
M
157-195.11
max, and
LS
p
520L0344 | BC00000038en-US0802
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