Fan Drive Control (FDC), options: F1 (12V) / F2 (24V)
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.
Schematic diagram
PT
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.
Refer to Hydraulic Fan Drive Design Guidelines, 520L0926 for detailed information necessary to properly
size and configure a hydraulic fan drive system.
Warning
The FDC is for Fan Drive systems only! 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.
Technical Information
H1 Axial Piston Single Pumps, Size 069/078
Control options
30 11062169 • Rev 0700 • November 2015
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