1. Basic Information – D634‑548

• Manufacturer: MOOG Inc.

• Model: D634‑548

• Series: D634 (Direct Drive Servo Valve, DDV)

• Type: Single‑stage, pilotless, direct‑drive servo valve

• Mounting: ISO 4401‑05 (NG10)

• Actuation: Permanent magnet linear force motor

• Feedback: Integrated LVDT spool position closed‑loop

• Electronics: Integrated 24 VDC PWM drive

• Protection: IP65

• Weight: ≈ 6.3 kg (13.9 lb)

2. Hydraulic Specifications

• Max working pressure (P, A, B): 350 bar (5,000 psi)Moog Inc.

• Max T‑port pressure (no Y port): 50 bar (725 psi)Moog Inc.

• Max T‑port pressure (with Y port): 350 bar (5,000 psi)Moog Inc.

• Rated flow (Δp = 35 bar): 100 L/min (26.4 gpm)

• Max flow: ≈ 185 L/min (48.8 gpm)

• Null leakage: 2.5–7 L/min (max, axis cut)

• Fluid: Mineral hydraulic oil per ISO 11158 / DIN 51524

• Viscosity: 15–100 mm²/s (5–400 mm²/s allowed)

• Fluid temperature: −20 °C … +80 °C

3. Electrical Specifications

• Supply voltage: 24 VDC (range 18–32 VDC)Moog Inc.

• Max current: 2.5 AMoog Inc.

• Control signals: ±10 V, ±10 mA, 4–20 mAMoog Inc.

• Connector: 6+PE (IP65)Moog Inc.

• Electronics: Integrated SMD, PWM current output

4. Dynamic Performance (Typical)

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

• −3 dB bandwidth: 18–35 Hz

• Hysteresis: <0.25% of full scale

• Resolution: <0.10% of full scale

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

5. Design & Features

• Pilotless direct drive: No pilot oil supply needed; simpler circuit, lower leakage

• Linear force motor: High force, bidirectional drive; performance nearly independent of supply pressure

• Integrated LVDT closed loop: Accurate, repeatable spool positioning

• Spring centering: Auto‑return to neutral on power loss (safe fail)

• Low null current: Reduced power consumption near zero flow

• High contamination resistance: Suitable for tough industrial environments

6. Typical Applications

• Heavy‑duty hydraulic presses & forging equipment

• Large injection molding & die‑casting machines

• Multi‑axis vibration / fatigue test benches

• Steel & metal industry hydraulic controls

• High‑precision closed‑loop position / force / velocity systems