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
electrical 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.
The pump displacement is proportional to the solenoid signal current, but it also depends upon pump
input speed and system pressure. This characterisistic also provides a power limiting function by
reducing the pump swashplate angle as sytem pressure increases. The pump should be configured with
0.8 mm control orifices to provide slowest response and maximize system stability. Additionally pressure
limiter (PL) valves are used to limit maximum fan trim speed in both (forward and reverse) directions.
FDC control
P301 441
FDC hydraulic schematic
P
T
F00B
M14
C1
C2
F00A
P301 442
H1 pumps with FDC will be delivered from factory with nominal PL setting of 150 bar [2175 psi]. The PL
must be re-adjusted to ensure that the fan reaches the desired fan speed to satisfy the cooling needs of
the system. HPRV setting must be always at least 30 bar [435 psi] higher than PL setting.
Under some circumstances, such as contamination, the control spool could stick and cause the pump to
stay at some displacement.
For more information necessary to properly size and configure a hydraulic fan drive system, see
Hydraulic
Fan Drive Design Guidelines
AB00000019.
Use in other systems could result in unintended movement of the machine or it’s elements. Loss of the
input signal to this control will cause the pump to produce maximum flow.
The FDC is for Fan Drive systems only!
Technical Information
H1 Axial Piston Single Pumps, Size 045/053
Control Options
©
Danfoss | May 2017
11063344 | BC00000059en-US1001 | 31
