Fan Drive Control (Fdc); Control Signal Requirements, Fdc 115/130 - Danfoss H1 Series Technical Information

Technical Information
H1P 115/130 Axial Piston Single Pumps
Control Options

Fan Drive Control (FDC)

32 | © Danfoss | May 2018
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.
FDC control
P301 441
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.
H1 pumps with FDC will be delivered from factory with nominal pressure limiter 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!
Due to the fail-safe functionality of the FDC control the pump will stroke to max. displacement in case the
input signal to the pump control and the Diesel engine will be switched off at the same time. In this
situation a low loop event can occur which may damage the pump. Therefore, it's strictly recommended
to keep the input signal to the pump control alive while switching off the engine.
For further information please contact your Danfoss representative.

Control Signal Requirements, FDC 115/130

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 swash plate angle as system pressure increases.
A typical response characteristic is shown in the accompanying graph below:
FDC schematic
M14
C1
F00B F00A
C2
T P
P301 442
BC00000198en-US0901