Danfoss Series 42

the pump to hold very accurately at the commanded displacement. Centering springs and internal
moments return the swashplate to neutral position in the absence of control input.
EDC on series 42 pump
High current electrical displacement control (HC-EDC)
The High Current Electrical Displacement Control (HC-EDC) is a two-stage control using a DC input
current with Pulse With Modulation (PWM) to control pump displacement. Stage one uses two
Proportional Pressure Reducing Valves (PPRV), to provide reducing pressure proportional to the input
current. The pressure from each PPRV is provided to each end of the sensing piston in the control: this is
stage one. The sensing piston is connected to the control spool in the pump by a pin and linkage. The
control spool modulates the differential pressure across the pump’s servo piston, this is stage two. The
angle of the swashplate is proportional to the input current.
A mechanical feedback linkage moves the control spool toward neutral as the swashplate angle reaches
the commanded position. Mechanical feedback allows the pump to hold very accurately at the
commanded displacement. Centering springs and internal moments return the swashplate to neutral
position in the absence of control input.
HC-EDC on series 42 pump
Non-feedback proportional hydraulic (NFPH) control
The Non-Feedback Proportional Hydraulic (NFPH) control is a hydraulic displacement control. External
valving supplies an input pressure directly to the pump servo piston via control ports X1 and X2 to
control pump displacement.
Pump displacement is proportional to the pressure difference across the servo piston. However, because
this control does not use mechanical feedback, displacement also depends upon input speed and system
Service Manual
Series 42 Axial Piston Closed Circuit Pumps
Control Options
18 520L0638 • Rev 0300 • July 2015