Servovalves
with integrated Electronics
D791 and D792 Series
2
3
Q [l/min] = max. flow
Δp [bar] = valve pressure drop
with Q
A
K
[cm
2
] = spool drive area
p
X
[bar] = pilot pressure
The pilot pressure p
X
has to be at
least 15 bar above the return
pressure of the pilot stage.
D791 and D792 Series
Three stage servovalves
Principle of operation
An electrical command signal (set
point, input signal) is applied to
the integrated control amplifier
which drives a current through
the pilot valve coils. The pilot valve
produces differential pressure in
its control ports. This pressure
difference results in a pilot flow
which causes main spool dis-
placement.
The position transducer which is
excited via an oscillator measures
the position of the main spool
(actual value, position voltage).
This signal then is demodulated
and fed back to the control
amplifier where it is compared
with the command signal. The
control amplifier drives the pilot
valve until the error between
command signal and feedback
signal is zero. Thus, the position of
the main spool is proportional to
the electrical command signal.
QQ
p
p
N
N
=
Δ
Δ
p 2,5 10
Q
A
p
X
-2
K
≥⋅⋅ Δ
The actual flow depends on the
electrical command signal and
the valve pressure drop, and may
be calculated using the square
root function for a sharp-edged
orifice.
The flow value Q calculated in
this way should not exceed an
average flow velocity of 30 m/s in
ports P, A, B and T.
Q [l/min] = calculated flow
Q
N
[l/min] = rated flow
Δp [bar] = actual valve pressure
drop
Δp
N
[bar] = rated valve pressure
drop
Operational features
❒ Electrical position feedback with pressure isolated position
transducer (LVDT), no wear
❒ Integrated SMD electronics with false polarity protection
❒ Optional external pilot supply and return connections via fifth
and sixth port in valve body
❒ Low threshold and hysteresis, excellent null stability
❒ Preadjusted at factory
4
If large flow rates with high valve
pressure drops are required, an
appropriate higher pilot pressure
has to be chosen to overcome the
flow forces. An approximate value
can be calculated as follows:
The valves D791 and D792 Series
described in this catalogue have
successfully passed EMC tests
required by EC Directive. Please
take notice of the respective
references in the electronics
section.
Our quality management system
is certified in accordance with
DIN EN ISO 9001.
This catalogue is for users with
technical knowledge. To ensure
that all necessary characteristics
for function and safety of the
system are given, the user has to
check the suitability of the
products described here.
In case of doubt please contact
Moog.
The flow control servovalves D791
and D792 Series are throttle valves
for 3-way and preferably 4-way
applications. These three stage
servovalves have been especially
developed for such demanding
applications where high flow rates
and at the same time extreme
dynamic performance require-
ments must be met. The design of
these valves is based on the well
known D079 Series. The inte-
grated electronics has been
replaced by a new design applying
SMD technology. The valves are
offered with pilot valves of D761
or D765 Series, optional standard
response or high response versions
are available. Series D791 can de-
liver rated flow up to 250 l/min,
Series D792 is available with rated
flow up to 1000 l/min.
These valves are suitable for pres-
sure or force control, position and
velocity control systems with high
dynamic response requirements.
D791 and D792 Series
General technical data
Operating pressure range
Main stage
Ports P, A and B
with X internal up to 315 bar
with X external up to 350 bar
Port T with Y internal up to 210 bar
Port T with Y external up to 350 bar
Pilot valve
Ports P, A and B
D761, D765 Series up to 315 bar
Port T up to 210 bar
Temperature range
Ambient -20 to +60 °C
Fluid -20 to +80 °C
Seal material FPM, others on request
Operating fluid Mineral oil based hydraulic fluid
(to DIN 51524), others on request
Viscosity recommended 15 to 100 mm²/s
Class of cleanliness The cleanliness of the hydraulic
fluid greatly effects the per-
formance (spool positioning, high
resolution) and wear (metering
edges, pressure gain, leakage) of
the valve.
5
T B P A
3 stage Servovalve D792
with Pilot valve D765 Series
Recommended cleanliness class
for normal operation: ISO 4406 < 17/14/11
for longer life: ISO 4406 < 16/13/10
System filtration
Pilot valve: High pressure filter (without by-
pass, but with dirt alarm) mounted
in the mainflow and if possible,
directly upstream of the servo-
valve.
Main stage: Main stage: high pressure filter as
for the pilot stage. In combination
with a fast regulating VD-pump a
bypass filter is possible.
Filter rating recommended
for normal operation: ß
10
≥ 75 (10 μm absolute)
for longer life: ß
5
≥ 75 ( 5 μm absolute)
Installation options any position, fixed or movable
Vibration 30 g, 3 axes
Degree of protection EN 60529: IP 65 (with mating con-
nector mounted)
Shipping plate Delivered with an oil sealed ship-
ping plate
6
Model . . . .Type D791 . . . . S . . .
Mounting pattern ISO, but X and Y do not corres- ISO 10372-06-05-0-92
pond to ISO
Valve body version 4-way
3-stage with bushing spool assembly
Pilot valve 2-stage, optional D761 or D765 Series
Pilot connection optional, internal or external X and Y
Mass [kg] 13
Rated flow (± 10%) at Δp
N
= 35 bar
per land [l/min] 100 160 250
Response time* for 0 to 100% stroke (depen-
dent on pilot valve) [ms] 3 to 10
Threshold* [%] < 0,2
Hysteresis* [%] < 0,5
Null shift with ΔT = 55 K [%] < 2
Null leakage flow* total, max. [l/min] 5 7 10
Pilot leakage flow* max., for 100% step input (de-
pendent on pilot valve) [l/min] 4 to 11
Main spool stroke [mm] 1,4 1,2 2,0
Main spool drive area [cm²] 2,85
* measured at 210 bar pilot or operating pressure, fluid viscosity of 32 mm²/s and fluid temperature of 40 °C
Valve flow diagram
Typical characteristic curves
measured at 210 bar pilot or operating pressure, fluid viscosity of 32 mm²/s and fluid temperature of 40 °C
Valve flow for maximum valve opening (100% command
signal) as a function of the valve pressure drop
Frequency response
for valves with different rated flows and different pilot valves
D791 Series
Technical data
Rated flow 100/160 l/min
Pilot valve D761 Std 10 l/min
Rated flow 100/160 l/min
Pilot valve D765 HR10 l/min
Rated flow 250 l/min
Pilot valve D761 Std10 l/min
Rated flow 250 l/min
Pilot valve D761 HR 20 l/min
Model . . . .Type D792 . . . . S . . .
Mounting pattern Moog Standard
Valve body version 4-way
3-stage with bushing spool assembly
Pilot valve 2-stage, optional D761 or D765 Series
Pilot connection optional, internal or external X and Y
Mass [kg] 17
Rated flow (± 10%) at Δp
N
= 35 bar
per land [l/min] 400 630 800 1000
Response time* for 0 to 100% stroke (depen-
dent on pilot valve) [ms] 4 to 12
Threshold* [%] < 0,2
Hysteresis* [%] < 0,5
Null shift with Δ T = 55 K [%] < 2
Null leakage flow* total, max. [l/min] 10 14 14 14
Pilot leakage flow* max., for 100% step input (de-
pendent on pilot valve) [l/min] 6 to 16
Main spool stroke [mm] 1,8 1,9 2,6 4,0
Main spool drive area [cm²] 3,8 7,14 7,14 7,14
* measured at 210 bar pilot or operating pressure, fluid viscosity of 32 mm²/s and fluid temperature of 40 °C
Valve flow diagram
Typical characteristic curves
measured at 210 bar pilot or operating pressure, fluid viscosity of 32 mm²/s and fluid temperature of 40 °C
Frequency response
for valves with different rated flows and different pilot valves
D792 Series
Technical data
Rated flow 800 l/min
Pilot valve D765 HR 20 l/min
Rated flow 800 l/min
Pilot valve D761 HR 20 l/min
Rated flow 400 l/min
Pilot valve D761 HR 20 l/min
Rated flow 630 l/min
Pilot valve D765 HR 20 l/min
7
Valve flow for maximum valve opening (100% command
signal) as a function of the valve pressure drop
D791 Series
Installation drawing with
Pilot valve D761 Series
Conversion instruction
The mounting manifold must
conform to ISO 10372-06-05-0-92.
Note: The X port to ISO Stan-
dard must not be machined.
The X and Y ports of Moog
valve body do not correspond
to ISO Standard.
Mounting surface needs to be
flat within 0,02 mm. Average
surface finish value, Ra, better
than 1μm.
PAB TGX YF1F2F3F4
Ø16 Ø16 Ø16 Ø16 Ø8 Ø6 Ø6 M10 M10 M10 M10
x 36,5 11,1 61,9 36,5 11,1 36,5 36,5 0 73 73 0
y 17,4 42,8 42,8 68,2 23,7 -2,6 88,2 0 0 85,6 85,6
8
9
Spare parts and accessories for D791 Series
O-rings (included in delivery) FPM 85 Shore
for P, T, A, B 4 pieces ID 20,3 x 1,78 as service seal set
for X, Y 2 pieces ID 7,65 x 1,78 B97215-V791-22
Mating connector, waterproof IP 65 (not included in delivery) for cable dia
6+PE-pole DIN 43563 min. Ø 10 mm, max. Ø 12 mm B97007 061
Flushing plate (internal supply) 55118 001
(external supply) A26133
Mounting bolts (not included in delivery)
M 10 x 50 DIN 912-10.9 4 pieces required torque 65 Nm A03665 100 050
Replaceable filter for pilot valve 65 μm nominal A67999 065
O-rings for filter replacement and pilot valve FPM 85 Shore
Service seal set 1 piece B97215-V761F76
D791 Series
Installation drawing with
Pilot valve D765 Series
Spare parts, Accessories
10
Note: The X and Y tubes have to
be connected to the Moog valve
body by fittings.
Mounting surface needs to be flat
within 0,02 mm. Average surface
finish value, Ra, better than 1μm.
D792 Series
Installation drawing with
Pilot valve D761 Series
Conversion instruction
P A B T G F1F2F3F4F5F6 F7F8
Ø28 Ø28 Ø28 Ø28 Ø8 M16 M16 M16 M16 M16 M16 M16 M16
x 55,4 15,8 95,0 55,4 55,4 0 110,8 110,8 0 31,5 79,3 79,3 31,5
y 30,1 58,7 58,7 87,3 0 0 0 117,4 117,4 0 0 117,4 117,4
D792 Series
Installation drawing with
Pilot valve D765 Series
Spare parts, Accessories
Spare parts and accessories for D792 Series
O-rings (included in delivery) FPM 85 Shore
for P, T, A, B 4 pieces ID 36 x 3,5 as service seal set B97215-V792-22
Mating connector, waterproof IP 65 (not included in delivery) for cable dia
6+PE-pole DIN 43563 min. Ø 10 mm, max. Ø 12 mm B97007 061
Flushing plate 76216 001
Mounting bolts (not included in delivery) required
M 16 x 60 DIN 912-10.9 8 pieces required torque 290 Nm A03665 160 060
Replaceable filter for pilot valve 65 μm nominale A67999 065
O-rings for filter replacement and pilot valve FPM 85 Shore
Service seal set 1 piece B97215-V761F76
11
12
General requirements
D791 and D792 Series
Valve electronics with
supply voltage ± 15 Volt
Command signal 0 to ±10 V
Valves with voltage command
input
The spool stroke of the valve is
proportional to (U
D
– U
E
). 100%
valve opening P A and B T is
achieved at (U
D
– U
E
) = +10 V. At
0 V command the spool is in a
centred position.
The input stage is a differential
amplifier. If only one command
signal is available, pin D or E is
connected to signal ground ⊥
(pin C) according to the required
operating direction (to be done at
the mating connector).
Command signal 0 to ±10 mA
Valves with current command
input
The spool stroke of the valve is
proportional to (I
D
– I
E
). 100%
valve opening P A and B T is
achieved at (I
D
– I
E
) = +10 mA. At
0 mA command the spool is in a
centred position.
Either pin D or E is used according
to the required operating direc-
tion. The unused pin is left open
(not connected at the mating con-
nector). The input pins D and E are
inverting.
Actual value 0 to ±10 V
Valves with voltage command
input
The actual spool position value
can be measured at pin F. This
signal can be used for monitoring
and fault detection purposes.
The spool stroke range corres-
ponds to ±10 V. 100% valve ope-
ning P A and B T corresponds
to +10 V.
Actual value 0 to ±10 mA or
4 to 20 mA
Valves with current command
input
The actual spool position value
can be measured at pin F. This
signal can be used for monitoring
and fault detection purposes.
The spool stroke range cor-
responds to ±10 mA (4 to 20 mA).
100% valve opening P A and
B T corresponds to +10 mA
(20 mA).
Supply ± 15 VDC ± 3%. Ripple <50 mV
pp
. Current consumption
max. ± 250 mA
All signal lines, also those of external transducers, shielded
Shielding connected radially to ⊥ (0V), power supply side, and
connected to the mating connector housing (EMC)
EMC: Meets the requirements of EN 55011/03.91 class B,
EN 50081-1/01.92, and EN 50082-2/03.95, performance criterion
class A
Protective grounding lead ≥ 0,75mm
2
Note: When making electrical connections to the valve (shield,
protective grounding) appropriate measures must be taken to
ensure that locally different earth potentials do not result in excessive
ground currents. See also Moog Application Note AM 353 E.
Wiring for valves with 6+PE pole connector to DIN 43563 and mating connector (metal shell) with leading protective grounding
connection (
).
Input rated command 0 to ± 10 mA 0 to ± 10 V
Valve flow Load resistance (diff.) 1 kΩ Input resistance 10 kΩ
Input rated command
(differential)
Valve flow
Output actual value 0 to ± 10 mA 0 to ± 10 V
Main spool position Load resistance max. 500 Ω Output resistance 50 Ω
Function Current command Voltage command
Supply + 15 VDC ± 3
Supply – 15 VDC ± 3
Supply / signal ground ⊥ (0V)
Input command I
D
= –I
E
: 0 to ±10 mA
Input command (inverted) I
E
= –I
D
: 0 to ±10 mA
U
D–E
= 0 to ±10 V
(R
e
= 10 kΩ)
(R
e
= 200 Ω)
Input voltage for U
D–B
and U
E–B
for both signal types is limited to min. –15 V and max. +32 V
Protective grounding
D791 and D792 Series
Valve electronics with
supply voltage 24 Volt
Actual value 4 to 20 mA
The actual spool position value
can be measured at pin F (see
diagram below). This signal can
be used for monitoring and fault
detection purposes.
The spool stroke range corres-
ponds to 4 to 20 mA.
The centred position is at 12 mA.
20 mA corresponds to 100 %
valve opening P A and B T.
The position signal output 4 to
20 mA allows to detect a cable
break when I
F
= 0 mA.
For failure detection purposes it
is advised to connect pin F of
the mating connector and route
this signal to the control
cabinet.
Command signal 0 to ±10 V,
Valves with
voltage command input
The spool stroke of the valve is
proportional to (U
D
– U
E
).
100 % valve opening P A and
B T is achieved at (U
D
– U
E
) = +10 V.
At 0 V command the spool is in
centred position.
The input stage is a differential
amplifier. If only one command
signal is available, pin D or E is
connected to signal ground at
cabinet side, according to the
required operating direction.
Command signal 0 to ±10 mA
floating,
Valves with
current command input
The spool stroke of the valve is
proportional to I
D
= –I
E
.
100 % valve opening P A and
B T is achieved at I
D
= +10 mA.
At 0 mA command the spool is
in centred position.
The input pins D and E are inver-
ting. Either pin D or E is used
according to the required ope-
rating direction. The other pin is
connected to signal ground at
cabinet side.
General requirements
Supply 24 VDC, min. 18 VDC, max. 32 VDC
Current consumption max. 300 mA
All signal lines, also those of external transducers, shielded.
Shielding connected radially to ⊥ (0 V), power supply side, and
connected to the mating connector housing (EMC).
EMC: Meets the requirements of EN 55011:1998, class B,
EN 50082-2:1995, performance criterion class A.
Minimum cross-section of all leads ≥ 0,75 mm
2
.
Consider voltage losses between cabinet and valve.
Note: When making electric connections to the valve (shield, protective
earth) appropriate measures must be taken to ensure that locally
different earth potentials do not result in excessive ground currents.
See also Moog Application Note AM 353 E.
Circuit diagram for measu-
rement of actual value I
F
(position of main spool)
Wiring for valves with 6+PE pole connector
to EN 175201 Part 804
2
), and mating connector (type R and S , metal shell) with leading protective earth connection ( ). See also wiring
instructions AM 426 E.
Note: Enable input
With enable signal off, the main
spool will move to a safe position.
a) Centred position
(unbiased pilot valve)
function code A
1
)
b) End position
(biased pilot valve)
function code B
1
)
1
) see type designation
Supply 24 VDC (min. 18 VDC, max. 32 VDC). I
max
= 300 mA
Supply / Signal ground ⊥ (0 V)
Enabled U
C–B
> +8,5 VDC
Not enabled U
C–B
< +6,5 VDC
Protective earth
Output actual value
spool position
Input rated command
(differential)
I
e
= 2,0 mA at 24 VDC (see note above)
I
F–B
= 4 to 20 mA. At 12 mA spool is in centred position. R
L
= 100 to 500 Ω
Signal code D (see page 7): U
F–B
= 2 to 10 V. At 6 V spool is in centred position. R
a
= 500 Ω
Input command I
D
= –I
E
: 0 to ±10 mA
Input command (inverted) I
E
= –I
D
: 0 to ±10 mA
U
D–E
= 0 to ±10 V
(R
e
= 10 kΩ)
(R
e
= 200 Ω)
Input voltage for U
D–B
and U
E–B
for both signal types is limited to min. –15 V and max. +32 V
Function Current command Voltage command
2
) formerly DIN 43563
13
Notes
14
Specification status
- Series specification
E Preseries specification
Z Special specification
D791 und D792 Series
Ordering information
15
Model designation
assigned at the factory
Valve version
S Servovalve 3-stage
Rated flow
Q
N
[l/min] at Δp
N
= 35 bar per land Series
10 100 D791
16 160 D791
25 250 D791
40 400 D792
63 630 D792
80 800 D792
99 1 000 D792
Main spool type
O 4-way: axis cut, linear characteristic
Pilot valve
P D761 Standard
Q D761 High response
R D765 High response
1
)
1
) only together with ± 15 V
S D765 Standard
1
) (see supply voltage)
Factory identification
assigned at the factory
Maximum operating pressure p
P
J 315 bar. At p
X
≤ 315 bar (X and Y external) operating pressure
in ports P, A, B and T up to 350 bar possible
K 350 bar
Spool position of main stage without electrical supply
Position Pilot pressure [bar]
O undefined ≥15
A P B, A T ≥15
B P A, B T ≥15
others on request
Preferred configurations are highlighted.
All combinations may not be available.
Options may increase price.
Technical changes are reserved.
Supply voltage
0 ± 15 VDC ± 3%, Ripple < 50 mV
pp
2 24 VDC (18 to 32 VDC)
D791, D792
Valve connector
S 6 + PE-pole DIN 43563
Type designationModel-Number
Pilot connections and pressure
Supply X Return Y
4 internal internal
5 external internal
6 external external
7 internal external
Seal material
U FPM (Viton), PUR (Ultrathan) only for bushing
V FPM (Viton)
Function code
O 24 V Without enable input
P 15 V Without enable input
A 24 V Without enable signal applied
the spool moves to adjustable
centered position (see page 13).
B 24 V Without enable signal applied the
spool moves into defined end posi-
tion A T bzw. B T (see page 13).
Parameters of the control electronics are
adapted to the pilot pressure. See opera-
ting pressure on the nameplate and in this
ordering information.
Signals for 100% spool stroke
Input Output
A ±10 V ±10 V
X ±10 mA, floating ±10 mA
KRH/WA/50 Printed in Germany
Moog GmbH
Hanns-Klemm-Straße 28
D - 71034 Böblingen
Postfach 1670
D - 71006 Böblingen
Telefon (07031) 622-0
Telefax (07031) 622-191
Australia Melbourne
Austria Vienna
Brazil São Paulo
Denmark Birkerød
England Tewkesbury
Finland Espoo
France Rungis
Germany Böblingen
Hong Kong Kwai Chung
India Bangalore
Ireland Ringaskiddy
Italy Malnate
Japan Hiratsuka
Korea Kwangju
Philippines Baguio
Russia Pavlovo
South Africa Midrand City
Singapore Singapore
Spain Orio
Sweden Gotenborg
USA East Aurora (NY)
D791/2 - EN / 01.04
