1. Model Definition

• D634: ISO 4401 Size 05 direct drive servo valve series

• 388: Ultra‑high flow, high‑dynamic configuration

• C: Revision C

2. Hydraulic Specifications

• Mounting: ISO 4401‑05 (NG10)

• Max working pressure (P/A/B): 350 barMoog Inc.

• T‑port pressure (no Y): ≤ 50 barMoog Inc.

• Rated flow (Δp = 35 bar): 240 L/min

• Peak flow: approx. 320 L/min

• Internal leakage: ≤ 4.5 L/min

• Fluid: ISO 11158 mineral oil

• Fluid temperature: −20 °C ~ +80 °C

• Fluid cleanliness: ISO 4406 17/14/11

• Weight: approx. 8.2 kg

3. Dynamic Performance

• Full‑stroke step response: ≤20 msMoog Inc.

• −3 dB bandwidth: 55–65 Hz

• Hysteresis: <0.25% full scale

• Resolution: <0.12% full scale

• Null drift (ΔT = 55 K): <1.5% full scale

4. Electrical Specifications

• Supply: 24 VDC (18–32 VDC)Moog Inc.

• Max operating current: 4.0 A

• Standard command: ±10 VMoog Inc.

• Optional command: ±10 mA / 4–20 mAMoog Inc.

• Spool position feedback: 0–10 VDC

• Connector: M18, 6‑pin + PE, IP65

• Ambient temperature: −20 °C ~ +60 °C

• EMC: CE compliant

5. Key Features

• Pilotless direct drive: Permanent‑magnet linear force motor, no pilot oil required

• Ultra‑high flow: Optimized for large‑scale, high‑speed hydraulic systems

• Pressure‑independent dynamics: Stable response under varying loads

• Closed‑loop control: Integrated LVDT for precise spool position feedback

• Fail‑safe: Spring‑centered, returns to neutral on power loss

• Integrated electronics: Compact, rugged, PWM‑driven, EMI‑hardened design

6. Typical Applications

• Heavy‑duty hydraulic presses, forging & extrusion machines

• Large aerospace/automotive component test rigs

• High‑force vibration simulators

• Industrial closed‑loop position, velocity, and pressure control systems

7. Pin Assignment

1. +24 VDC Power

2. Power Ground

3. Command +

4. Command −

5. Position Feedback Output

6. Feedback Ground

   PE: Protective Earth

   Shielded twisted pair recommended for signal wiring.