AFS20D | Yokogawa CENTUM VP Duplexed Field Control Unit

Product Overview

The AFS20D is a duplexed field control unit (FCU) for the Yokogawa CENTUM VP and CENTUM CS 3000 distributed control systems. It executes continuous and sequence control strategies with dual-redundant processors, power modules, and communication buses to maintain uninterrupted process control under hardware fault conditions. The unit features a VR5432 RISC processor at 133 MHz with 16 MB of battery-backed main memory.

Key Specifications

• System: Yokogawa CENTUM VP / CENTUM CS 3000
• Type: Duplexed Field Control Unit
• Processor: VR5432 RISC CPU, 133 MHz
• Main Memory: 16 MB
• Memory Backup: Battery-backed, max. 72 hours retention
• Battery Recharge Time: Minimum 48 hours
• Power Consumption:
  • 100–120 V AC: 1700 VA
  • 220–240 V AC: 2000 VA
  • 24 V DC: 50 A
• Network: Dual-redundant V net, dual-redundant RIO bus
• FCU Status Contact: 3 terminals (NC, NO, C), 250 V AC / 30 V DC, max. 2 A
• Mounting: Integrated cabinet, standard rack installation
• Weight: Approx. 250 kg (base cabinet), 400 kg (fully loaded)
• Operating Temperature: 0°C to +55°C
• Power Terminals: M6 / Grounding: M8 / Contact Terminals: M4

Features & Benefits

1. Dual-Redundant Everything: Redundant CPU, power supply, V net, and RIO bus ensure no single point of failure can interrupt process control.
2. High Power Capacity: Supports up to 1700 VA (AC) or 50 A (DC) to drive extensive I/O configurations and node units.
3. 72-Hour Memory Retention: Battery-backed RAM preserves the entire control strategy and process state during extended outages.
4. Heavy-Duty Cabinet: Robust cabinet design supports up to 400 kg fully loaded, accommodating numerous I/O modules and power supplies.
5. Status Contact Output: Form-C relay contact provides external alarm indication for FCU failure or switchover events.

FAQ

Q: What is the difference between AFS20D and AFG20D?
A: The AFS20D is a standard duplexed FCU with 16 MB memory. The AFG20D is an enhanced duplexed FCU with 32 MB memory for larger control strategies.

Q: How many I/O points can the AFS20D support?
A> The AFS20D supports extensive I/O through the RIO bus. Exact point count depends on the number and type of remote I/O racks and modules installed.

Q: What power supply should I specify?
A> Select the suffix code matching your plant standard: -11 for 100–120 V AC, -12 for 220–240 V AC, or -14 for 24 V DC.

Installation Guide

• Install the cabinet on a reinforced concrete floor capable of supporting 400 kg.
• Connect redundant AC or DC power to the M6 power terminals.
• Connect the M8 grounding terminal to the plant earth bus.
• Connect V net cables to both primary and redundant control network segments.
• Connect RIO bus cables to remote I/O racks.
• Wire the FCU status contact (M4 terminals) to an external alarm or indicator circuit.
• Verify redundant failover by de-energizing the primary CPU or power supply.

Selection Tips

• Availability Requirements: The AFS20D is specified for processes where controller failure is unacceptable. For standard availability, consider the AFS20S single FCU.
• Cabinet Loading: Plan I/O module count to stay within the 400 kg fully loaded limit. Distribute heavy power supplies evenly within the cabinet.
• Battery Maintenance: Include battery replacement in your 3-year preventive maintenance schedule to ensure 72-hour backup capability.