Danfoss H1 Basic Information

Fan Drive Control (FDC)
The Fan Drive Control (FDC) is a non-feedback control in which an electrical input signal activates the
proportional solenoid that ports charge pressure to either side of the pump servo cylinder.
The single proportional solenoid is used to control pump displacement in the forward or reverse
direction.
The control spool is spring biased to produce maximum forward pump displacement in the absence of
an electrrical input signal. Based on the spring bias spool default forward flow for a CW rotation pump is
out of Port B while default forward flow for a CCW rotation pump is out of Port A.
FDC control
P301 441
FDC schematic
PT
F00B
M14
C1 C2
F00A
P301 442
Pump displacement vs. control current
100%
100%
Displacement
0
Signal Current (mA(DC
Avg
))
Max Current
H1 FDC control
N
a
b
a = Forward Threshold
b = Reverse Threshold
N = Neutral Override Current
P301 443
∆p = 0 bar
∆p = 0 bar
∆p = 300 bar
Reverse
Forward
The pump displacement is proportional to the solenoid signal current, but it also depends upon pump
input speed and system pressure. This characteristic also provides a power limiting function by reducing
the pump swashplate angle as system pressure increases. The pump should be configured with 0.8 mm
control orifices to provide slowest respponse and maximize system stability. Additionally pressure limiter
(PL) valves are used to limit maximum fan trim speed in both forward and reverse directions.
Under some circumstances, such as contamination, the control spool could stick and cause the pump to
stay at some displacement.
Basic Information
H1 Axial Piston Pumps, Single and Tandem
Operation
©
Danfoss | April 2017 11062168 | BC00000057en-US0602 | 15

Danfoss H1 Specifications

General

Brand	Danfoss
Model	H1
Category	Water Pump
Language	English