Control Operation And Description; Electric Controls; Electric Proportional Controls; Electric Two-Position Controls - Danfoss H1 Series Technical Information

Technical Information
H1 Bent Axis Variable Displacement Motors, Size 060/080/110/160/210/250

Control operation and description

Electric controls

Electric proportional controls

Electric two-position controls

Servo supply

36 | © Danfoss | December 2016
Motor displacement can be changed electro hydraulically under load in response to an electrical signal
from maximum displacement to minimum displacement and vice versa. Under some circumstances, such
as contamination, the control spool could stick and cause the motor to stay at some displacement.
The electric proportional control consists of a proportional solenoid which acts directly on a two-position,
three-way porting spool. When activated, the solenoid pushes on the spool which then ports high
pressure to the larger diameter of the servo piston. The servo piston and rotating group move to change
the displacement to the point where the pressures on the servo are in balance with the force from the
feedback spring.
De-energized = maximum displacement
With a de-energized to maximum displacement control, the de-energized proportional valve keeps the
motor at maximum displacement. When energized, the solenoid pushes on the porting spool which
moves to port high system pressure to the larger diameter end of the servo piston. Depending on the
current supplied to the proportional valve, the motor will stroke between maximum displacement at zero
current and minimum displacement at maximum current.
De-energized = minimum displacement
With a de-energized to minimum displacement control, the de-energized proportional valve keeps the
motor at minimum displacement. When energized, the solenoid pushes on the porting spool which
moves to port high system pressure to the larger diameter end of the servo piston. Depending on the
current supplied to the proportional valve, the motor will stroke between minimum displacement at zero
current and maximum displacement at maximum current.
The electric two-position control consists of an off/on-solenoid which acts on a two position, three-way
porting spool. Servo pressure is internally supplied to the two-position porting spool by an integral
system pressure shuttle.
De-energized = maximum displacement
When the solenoid is de-energized, the motor runs at maximum displacement. When energized, the
solenoid applies a force on the spool which ports high pressure to the larger diameter of the servo piston
and strokes the motor to minimum displacement. When the solenoid is de-energized, the motor strokes
back to maximum displacement.
De-energized = minimum displacement
When the solenoid is de-energized, the motor runs at minimum displacement. When energized, the
solenoid applies a force on the spool which ports the larger diameter of the servo piston to tank, and
strokes the motor to maximum displacement. When the solenoid is de-energized, the motor strokes back
to minimum displacement.
The system shuttle check valve supplies the control system with high system pressure. A minimum servo
supply pressure (high system pressure) of 20 bar above case pressure is required to shift the motor
displacement.
11037153 | BC00000043en-US1103