Specifications

OPERATION
➣ Electrical current in torque motor coils creates magnetic
forces on ends of armature.
➣ Armature and flapper assembly rotates about flexure sleeve
support.
➣ Flapper closes off one nozzle and diverts flow to that end of
spool.
➣ Spool moves and opens P
S
to one control port; opens other
control port to T.
➣ Spool pushes ball end of feedback spring creating a restoring
torque on the armature/flapper.
➣ As feedback torque becomes equal to torque from magnetic
forces, armature/flapper moves back to centered position.
➣ Spool stops at a position where feedback spring torque
equals torque due to input current.
➣ Therefore, spool position is proportional to input current.
➣ With constant pressures, flow to load is proportional to
spool position.
DP
L
P
S
T
T
A
B
Valve Responding
to Change in
Electrical Input
N
S
N
S
P
S
P
S
P
S
Flow to Actuator
P
S
T
T
P
S
A
B
Valve Condition
Following Change
N
S
N
S
P
S
P
S
NS
Operation
Operation
Operation
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