Nnes (Electric Displacement Control + Load Sensing Control) - Danfoss D1 Series Service Manual

Service Manual
D1 High Power Open Circuit Pumps Size 65/130/145/193/260
Operation

NNES (Electric Displacement Control + Load Sensing Control)

© Danfoss | July 2019
W
Warning
(1) Adjustment is not permissible
Electric Displacement Control (E) Principle
The electric displacement control uses an electric proportional solenoid valve to vary the pump's
displacement from minimum displacement to maximum displacement or from maximum displacement
to minimum displacement. The swashplate angle (pump displacement) is proportional to the electrical
input signal (control current).
Electric Displacement Control (E) Operation
This control is current driven, requiring a Pulse Width Modulated (PWM) signal. Pulse width modulation
allows more precise control of current to the solenoid. The PWM signal causes the solenoid pin to push
against the E spool, which depressurizes the end of servo piston, the swashplate angle increases under
the force of the bias piston
A swashplate feedback link provides swashplate position force to the solenoid through the E spool's
linear spring. The control reaches equilibrium when the position of the swashplate spring feedback force
exactly balances the input command solenoid force from the operator. As working pressure changes with
load, the control and servo/swashplate system work constantly to maintain the commanded position of
the swashplate.
Electric Displacement Control (E) Operating Instruction
To make sure the electric displacement control works properly, a minimum control pressure of 30 bar
[435 psi] is required. The required control pressure is taken either from the working pressure, or from the
externally applied control pressure at the E port.
If you can't make sure that the working pressure is above 30 bar all the time, then a minimum of 30bar
[435 psi] pressure supply at the E port is mandatory in order to control the displacement of the pump at
all times. This pressure supply can be provided from different sources, such as an additional small gear or
piston pump and a relief valve, or an accumulator.
If E port is not connected, remove the shuttle valve
D1P 130/145/193/260 NNES
E B B
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Vgmax
L3 S M4
L1527453 | AX00000292en-CN0201 | 17
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Vgmin
L1 L2