ABB Bailey 6640635A1 Hydraulic Servo Termination Unit

Product Overview

The ABB Bailey 6640635A1 is a Hydraulic Servo Termination Unit for the Bailey Infi 90 and Symphony DCS product families. It serves as the critical interface between the NTHS03 Hydraulic Servo Module and field hydraulic actuators, providing signal conditioning, termination, and protection for servo valve control loops in turbine and engine governor applications. The 6640635A1 ensures reliable transmission of low-level servo command signals while protecting sensitive control electronics from field-side electrical interference.

Key Technical Specifications

• Product Type: Hydraulic Servo Termination Unit
• Series: ABB Bailey Infi 90 / Symphony
• Associated Module: NTHS03 (Hydraulic Servo Module)
• Function: Servo valve signal termination and conditioning
• Assembly Number: 6640635A1
• Dimensions (L × W × H): 14.000" × 12.000" × 10.000"
• Shipping Weight: 5.000 lbs (2.27 kg)
• Product Weight: 530 g (0.53 kg) — per some sources
• Mounting: Panel or rack-mounted in Infi 90/Symphony cabinet
• Origin: USA / Canada

System Architecture

• NTHS03 Hydraulic Servo Module: The main control module that generates servo valve drive signals
• 6640635A1 Termination Unit: Provides field-side termination, filtering, and protection for servo outputs
• Hydraulic Actuator Interface: Connects to servo valves for precise positioning of fuel racks, steam valves, or guide vanes
• Feedback Loop: Supports LVDT or RVDT position feedback for closed-loop servo control

Key Features

• Signal Termination: Proper impedance matching and termination for servo drive signals
• Electrical Isolation: Protects NTHS03 module from field-side voltage transients
• Filtering: Reduces electrical noise on servo command signals for stable valve operation
• Overvoltage Protection: Safeguards control electronics from field wiring faults
• Rugged Construction: Industrial-grade design for continuous operation in power plant environments
• Easy Maintenance: Modular design allows replacement without rewiring field connections

Applications

• Steam turbine hydraulic servo control — fuel valve and steam valve positioning
• Gas turbine servo actuator drive — fuel metering and inlet guide vane control
• Hydro turbine wicket gate servo control
• Diesel engine fuel rack positioning systems
• Industrial hydraulic positioning systems requiring precise servo control

Installation Guide

1. Mount termination unit in Infi 90/Symphony control cabinet
2. Connect NTHS03 module output cables to termination unit input connectors
3. Wire servo valve drive signals from termination unit to field hydraulic actuators
4. Connect LVDT/RVDT feedback signals from actuator to termination unit feedback inputs
5. Verify proper grounding and shielding of all servo signal cables
6. Configure servo loop parameters via Bailey configuration software
7. Perform servo response testing and calibration

FAQ

Q: What is the relationship between 6640635A1 and NTHS03?
A: 6640635A1 is the termination unit assembly that interfaces the NTHS03 Hydraulic Servo Module to field servo valves. NTHS03 generates the control signals; 6640635A1 conditions and protects those signals for field use.

Q: What is the shipping weight?
A: Approximately 5.000 lbs (2.27 kg). Some sources list 530 g as the net product weight.

Q: Can this termination unit be used with other servo modules?
A: It is specifically designed for the NTHS03 module within the Infi 90/Symphony architecture. Verify compatibility with other modules before use.

Q: What type of feedback does it support?
A: LVDT (Linear Variable Differential Transformer) and RVDT (Rotary Variable Differential Transformer) position feedback signals for closed-loop servo control.

Model Selection Tips

• 6640635A1 = Hydraulic Servo Termination Unit for NTHS03 module
• Always pair with NTHS03 Hydraulic Servo Module for complete servo control functionality
• Verify servo valve electrical specifications (drive current, impedance) match termination unit ratings
• Confirm LVDT/RVDT feedback signal levels are compatible with Infi 90/Symphony input ranges
• For alternative servo control solutions, consider Woodward ProAct or MicroNet servo modules
• Check cable routing and shielding requirements for noise-sensitive servo signals