H1 pumps are limited in mechanical orifice combinations. Mechanical servo orifices are to be used only
for fail-safe return to neutral in a case of an electrical failure.
A swash-plate response times table is available for each frame size. Testing should be conducted to verify
the proper orifice selection for the desired response. Typical response times at the following conditions:
Δ p = 250 bar [3626 psi]
Charge pressure = 20 bar [290 psi]
Viscosity and temperature = 30 mm²/s [141 SUS] and 50 °C [122 °F]
Speed = 1800 min
-1
(rpm)
Response time, FNR
Stroking
direction
0.8 mm [0.03 in] orifice 1.0 mm [0.04 in] orifice 1.3 mm [0.05 in] orifice No orifice
28/32 38/45 28/32 38/45 28/32 38/45 28/32 38/45
Neutral to
full flow
2.1 s 2.6 s 1.1 s 1.6 s 0.8 s 1.1 s 0.7 s 0.7 s
Full flow to
neutral
1.1 s 1.8 s 0.9 s 1.0 s 0.6 s 0.7 s 0.3 s 0.3 s
Non Feedback Proportional Electric Control (NFPE)
The Non Feedback Proportional Electric (NFPE) control is an electrical automotive control in which an
electrical input signal activates one of two proportional solenoids that port charge pressure to either side
of the pump servo cylinder. The NFPE control has no mechanical feedback mechanism.
A 170 μm screen is located in the supply line immediately before the control porting spool.
Under some circumstances, such as contamination, the control spool could stick and cause the pump to
stay at some displacement.
Non Feedback Proportional Electric Control
NFPE schematic
P003 188
C2C1
F00A
M14
T PF00B
Service Manual
MP1
Operation
©
Danfoss | April 2019 AX00000244en-000201 | 27
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