Model Definition

D661 = Series (integrated electronics, 24 VDC, NG10)Moog Inc.

4688 = Spool/sleeve assembly; rated flow 200 L/min @ ΔP=35 bar

C = Pressure class variant; max working pressure 350 bar (P/A/B ports)Moog Inc.

Full config (typical: G55JOAA6VSX2HA):

G = ServoJet® pilot stage, standard spoolMoog Inc.

55 = Frequency response class (≥140 Hz bandwidth)

J = 24 VDC power, ±10 V / ±10 mA analog command

O = Null position: centered (fail‑safe, power‑off centering)

AA = Standard hydraulic/electrical base config

6 = 6+PE connector, IP65Moog Inc.

VS = Wide‑temperature sealing

X2HA = LVDT feedback, 4–20 mA output

Technical Specifications

Hydraulic Parameters

Rated flow: 200 L/min (ΔP=35 bar)

Max working pressure: 350 bar (P/A/B); 210 bar (internal drain T) / 350 bar (external drain T)Moog Inc.

Step response: 5–7 ms (0→100%, 210 bar)Moog Inc.

Hysteresis: <0.2%

Resolution: <0.1%

Null drift: <1.5% (ΔT=55 K)

Null leakage: <18 mL/min

Fluid cleanliness: NAS 1638 Class 6 / ISO 4406 18/15Moog Inc.

Electrical Parameters

Power supply: 24 VDC (18–32 VDC)Moog Inc.

Control signal: ±10 V (differential) or ±10 mAMoog Inc.

Feedback signal: 4–20 mA (LVDT spool position)

Connector: 6+PE, IP65Moog Inc.

Current draw: ≤500 mA

Physical & Environmental

Operating temperature: −40 ℃ to +85 ℃

Weight: approx. 9.5 kg

Interface & Communication Configuration

Hydraulic interface: P/A/B/T, ISO 4401‑05 (NG10)Moog Inc.

Electrical interface:

Power: 24 VDC, GND, PE

Command: ±10 V / ±10 mAMoog Inc.

Feedback: 4–20 mA (spool position)

Status: Fault alarm output

Core Functions

ServoJet® pilot stage: Superior contamination resistance, low null drift, extended service lifeMoog Inc.

Integrated high‑response amplifier: Built‑in PID, dead‑zone compensation, overload protectionMoog Inc.

LVDT closed‑loop feedback: High linearity and precision across full stroke

Fail‑Safe centering: Spool returns to neutral on power loss

G55 ultra‑high dynamics: ≥140 Hz bandwidth for extreme‑speed industrial applications

Application Scenarios

Metallurgy: Ultra‑high‑flow AGC roll gap control, tension control for heavy plate mills

Test equipment: High‑force dynamic material testers, ultra‑high‑frequency vibration tables

Industrial automation: Large CNC machine tools, high‑speed hydraulic presses, heavy‑duty injection molding machines

Energy & heavy industry: Wind turbine pitch control, shield machine main control, marine hydraulic systems

Usage & Maintenance

Installation: Horizontal/vertical mounting; avoid severe vibration

Fluid: ISO VG46 mineral oil; maintain cleanliness per NAS 1638 Class 6Moog Inc.

Commissioning: Apply 24 VDC power; connect ±10 V/±10 mA command; calibrate zero and gain via 4–20 mA feedback

Maintenance: Inspect fluid contamination regularly; calibrate zero/gain every 6 months; avoid long idle periods at high pressure