Pressure Compensating Override (Pcor) Option; Brake Pressure Defeat (Bpd) Option - Danfoss 51 Series Service Manual

Service Manual
Introduction
8
Series 51 Electrohydraulic Proportional Controls Service Manual

Pressure Compensating OverRide (PCOR) Option

The PCOR function allows the motor to match its displacement to the system load. The PCOR overrides
the control command allowing the motor to increase displacement when system pressure reaches a set
level due to load. This permits the motor to regulate system pressure by modulating the displacement of
the rotating group. As displacement increases, so does available torque while output speed decreases
and system pressure remains nearly constant at the PCOR setting.
The PCOR setting pressure is adjustable from 110 to 370 bar [1595 to 5365 psi]. Optional orifices at
locations T4, T5, T6, U6, and U7 regulate the speed of the PCOR operation.
PCOR
N27
N23
N23

Brake Pressure Defeat (BPD) option

The PCOR function can be equipped with a brake pressure defeat (BPD) option that defeats the PCOR
operation during dynamic braking. A shuttle spool in the multifunction block in front of the PCOR valve
directs only acceleration system pressure to the PCOR. During deceleration, the high dynamic braking
pressure is blocked from the PCOR. This limits rapid and uncontrolled pressures or engine over-speeding
while the vehicle/machine is slowing down. External hydraulic signal pressures fed to ports XA or XB are
essential to operate the BPD spool. PCOR operation on one-system pressure side is also an option.
EP, EQ Electrohydraulic Proportional Control with Pressure Compensator and Hydraulic Brake Pressure Defeat.
11009448 • Rev BA • July 2014
N18
N20
N29
N27
N14
N16
P101 906