Model Definition

D661 = Series (integrated electronics, 24 VDC, NG10)

4902 = Spool/sleeve assembly; rated flow 250 L/min @ ΔP=35 bar (high‑linearity, low‑leakage trim)

Typical full config example: P250HAAM7NSX2‑B

P250 = Max flow & ultra‑high frequency response

HAAM = Standard hydraulic layout, 24 VDC, ±10 V/±10 mA command, centered null

7 = 7+PE connector, IP65

NSX2 = NBR seals, wide temp range, LVDT 4–20 mA feedback

B = High‑linearity ServoJet® pilot stage

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: 17–21 ms (0→100%, 210 bar)

Hysteresis: <0.18%

Resolution: <0.08%

Null drift: <2.0% (ΔT=55 K)

Null leakage: <30 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: 7+PE, IP65

Current draw: ≤950 mA

Physical & Environmental

Operating temperature: −40 ℃ to +85 ℃

Weight: approx. 11.2 kg

Interface & Communication Configuration

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

Electrical interface:

Power: 24 VDC, GND, PE

Command: ±10 V / ±10 mA

Feedback: 4–20 mA (spool position)

Status: Fault alarm output

Core Functions

High‑Linearity ServoJet® Pilot: Better straight‑line flow characteristic, lower distortion

Integrated High‑Response Amplifier: Built‑in PID, dead‑zone compensation, overload protection

LVDT Closed‑Loop Feedback: High linearity and precision across full stroke

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

Max‑Flow Stability: Optimized for 250 L/min with smooth, stable response for large hydraulic systems

Application Scenarios

Metallurgy: High‑precision AGC roll gap control for heavy plate mills, high‑force tension control

Test equipment: Dynamic material testers, large‑scale high‑force vibration tables

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

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

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