Model Definition

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

4901 = Spool/sleeve assembly; rated flow 250 L/min @ ΔP=35 bar

Typical full config example: P250HAAM7NSX2‑A

P250 = Maximum flow & ultra‑high frequency response version

HAAM = Standard hydraulic layout, 24 VDC, ±10 V/±10 mA command, centered nullMoog Inc.

7 = 7+PE connector, IP65Moog Inc.

NSX2 = NBR seals, wide temperature range, LVDT feedback 4–20 mAMoog Inc.

A = Standard ServoJet® pilot stageMoog Inc.

Technical Specifications

Hydraulic Parameters

Rated flow: 250 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: 18–22 ms (0→100%, 210 bar)Moog Inc.

Hysteresis: <0.2%Moog Inc.

Resolution: <0.1%Moog Inc.

Null drift: <2.2% (ΔT=55 K)Moog Inc.

Null leakage: <32 mL/minMoog Inc.

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)Moog Inc.

Connector: 7+PE, IP65Moog Inc.

Current draw: ≤950 mA

Physical & Environmental

Operating temperature: −40 ℃ to +85 ℃Moog Inc.

Weight: approx. 11.0 kgMoog Inc.

Interface & Communication Configuration

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

Electrical interface:

Power: 24 VDC, GND, PEMoog Inc.

Command: ±10 V / ±10 mAMoog Inc.

Feedback: 4–20 mA (spool position)Moog Inc.

Status: Fault alarm output

Core Functions

ServoJet® pilot stage: Exceptional contamination resistance, minimal null drift, extended service lifeMoog Inc.

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

LVDT closed‑loop feedback: Superior linearity and precision across full strokeMoog Inc.

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

Max‑flow dynamics: Optimized for 250 L/min with stable response for extra‑large hydraulic systems

Application Scenarios

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

Test equipment: High‑precision dynamic material testers, large‑scale high‑force vibration tables

Industrial automation: Extra‑large CNC machine tools, ultra‑heavy‑duty hydraulic presses, large blow molding machines

Energy & heavy industry: Wind turbine pitch control (high‑power), marine main propulsion hydraulic systems, heavy‑duty steel mill hydraulic drives

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 feedbackMoog Inc.

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