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D634-358C

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D634-358C
May 25, 2026

D634-358C

The D634‑358C is a single‑stage, pilotless direct drive servo valve (DDV) in the MOOG D634 family, built to ISO 4401 Size 05 (NG10). It uses a permanent magnet linear force motor to drive the spool directly — no pilot oil required. An internal LVDT provides closed‑loop spool position feedback for excellent linearity and repeatability. Dynamic performance is largely independent of supply pressure, and spring centering ensures a fail‑safe return to neutral on power loss. Compared to 345C/346C: higher bandwidth, optimized for dynamic response, industrial‑grade robustness.

Description

1. General Description

The D634‑358C is a single‑stage, pilotless direct drive servo valve (DDV) in the MOOG D634 family, built to ISO 4401 Size 05 (NG10). It uses a permanent magnet linear force motor to drive the spool directly — no pilot oil required. An internal LVDT provides closed‑loop spool position feedback for excellent linearity and repeatability.
Dynamic performance is largely independent of supply pressure, and spring centering ensures a fail‑safe return to neutral on power loss.
Compared to 345C/346C: higher bandwidth, optimized for dynamic response, industrial‑grade robustness.

2. Model Code (D634‑358C)

  • D634: Series = Direct drive servo valve, ISO 4401 Size 05 (NG10)

  • 358: Configuration = high‑dynamic spool, 24 VDC industrial electronics, enhanced bandwidth

  • C: Revision C (current production baseline)

3. Hydraulic Specifications

  • Mounting: ISO 4401 Size 05 (NG10)

  • Max Working Pressure (P/A/B): 350 bar (5,000 psi)Moog Inc.

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

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

  • Rated Flow (Δp = 35 bar/orifice): 150 L/min (39.6 gpm)

  • Max Flow: ≈220 L/min

  • Internal Leakage: ≤3.2 L/min

  • Fluid: Mineral oil (ISO 11158 / DIN 51524)

  • Fluid Temp: −20 °C to +80 °C

  • Fluid Cleanliness: ISO 4406 17/14/11

  • Weight: ≈7.1 kg

4. Dynamic Performance

  • Full‑stroke Step Response: ≤22 msMoog Inc.

  • −3 dB Bandwidth: 50–60 Hz

  • Hysteresis: <0.2% full scale

  • Resolution: <0.1% full scale

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

5. Electrical Specifications

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

  • Max Operating Current: 2.6 A

  • Standard Command Signal: ±10 VMoog Inc.

  • Optional Signals: ±10 mA, 4–20 mAMoog Inc.

  • Spool Position Feedback: 0–10 VDC (or 4–20 mA)

  • Connector: M18, 6 pins + PE, IP65Moog Inc.

  • Ambient Temp: −20 °C to +60 °C

  • EMC: CE compliant

6. Key Features

  • Pilotless design: Simple installation, no external pilot supply

  • High dynamic response: 50–60 Hz bandwidth for fast‑acting systems

  • Pressure‑independent dynamics: Stable response under varying loads

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

  • Integrated electronics: Compact, protected, and ready for use

7. Typical Applications

  • High‑dynamic hydraulic presses

  • Structural vibration & fatigue test rigs

  • High‑speed industrial automation

  • Closed‑loop position/velocity/pressure control for high‑response machinery

8. Pin Assignment (6+PE)

  1. +24 VDC

  2. Power Ground

  3. Command +

  4. Command –

  5. Position Feedback Out

  6. Feedback Ground

    PE: Protective Earth

    Use shielded twisted pair for all signal wires.


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