FOXBORO P0928AY

Description

Product Overview

The FOXBORO P0928AY is a specialized power supply unit designed for the Foxboro I/A Series distributed control system (DCS), functioning specifically as a Field Power Supply. Unlike the main system power supply, this unit is dedicated to providing clean, regulated, and often redundant +24VDC power directly to field devices, such as transmitters, solenoid valves, and I/O isolators, within a control loop. The reliability of the FOXBORO P0928AY is essential for ensuring the integrity of field measurements and final control element operations.

Key Product Parameters

• Product Type: Field Device Power Supply

• Compatible System: Foxboro I/A Series DCS

• Input Voltage: Typically accepts AC input (e.g., 120/240VAC) for conversion to a DC field bus.

• Output Voltage: Provides a tightly regulated +24VDC output, the standard for powering most electronic field instruments.

• Output Current: Rated for a specific amperage (e.g., 5A, 10A) to support a segment of the field device network.

• Redundancy: Often designed to support N+1 redundant configuration when paired with an identical unit and a redundancy module, ensuring continuous power to critical field devices.

• Mounting: Standard 19-inch rack-mount form factor for installation in system or marshalling cabinets.

• Protections: Includes safeguards such as overcurrent protection, overvoltage protection, and thermal shutdown.

• Isolation: Provides galvanic isolation between the AC input and the DC output to protect field devices from power line disturbances.

Advantages and Core Features

The primary advantage of the FOXBORO P0928AY is its dedicated, industrial-grade design for powering sensitive field instrumentation. It offers superior voltage regulation and noise filtering compared to general-purpose power supplies, which is critical for maintaining the accuracy of analog signals (e.g., 4-20mA). Its support for hot-swappable, redundant configuration prevents single points of failure in the field power network, a key feature for process availability. The P0928AY is engineered for high reliability and easy integration within the I/A Series cabinet architecture, featuring status indicators for quick health assessment.

Application Scenarios

This power supply is used in Foxboro I/A Series systems to create isolated and reliable field power segments:

• Process Control Loops: Powering clusters of 4-20mA pressure, temperature, and flow transmitters in a refinery or chemical plant unit.

• Final Element Control: Supplying power to solenoid valves, I/P (current-to-pneumatic) converters, and positioner logic for control valves.

• Safety Systems: Providing dedicated power to field devices associated with Safety Instrumented Functions (SIFs).

• Discrete I/O Segments: Powering banks of proximity sensors or other digital field devices that require a 24VDC source.

• Remote I/O Enclosures: Serving as the local power source for field devices in a remote marshalling cabinet.

Comparison with Competing Products

Competing products include field power supplies from other DCS vendors like Emerson (DeltaV field power supplies), Honeywell, and ABB. The FOXBORO P0928AY is distinguished by its specific integration and validation within the Foxboro I/A Series system design. Compared to using multiple small, generic DIN-rail 24VDC power supplies, a centralized, redundant unit like the P0928AY offers better power quality management, simpler redundancy implementation, easier system diagnostics, and a cleaner cabinet layout.

Selection Guide and Important Notes

Selecting the FOXBORO P0928AY involves creating a field power segment strategy. Each segment’s total current draw from all connected field devices must be calculated.

Important Precautions:

• Power Segment Calculation: Meticulously sum the worst-case current consumption of every field device (including inrush currents for solenoids) assigned to the power segment served by the P0928AY. Do not exceed its rated output current.

• Redundancy Planning: For critical segments, always specify a redundant pair of supplies and the required redundancy module (e.g., P0928HY). Ensure the AC feed to each unit is from independent sources.

• Fusing & Protection: While the supply has internal protection, external fusing or circuit breakers on its output may still be required by design standards to protect downstream wiring.

• Heat Dissipation: Ensure adequate spacing and cabinet ventilation. These supplies generate heat, and overheating will reduce lifespan and reliability.

• Separation of Power: Field power from the P0928AY should be kept strictly separate from system logic power (e.g., from a P0904AK) to prevent noise coupling and to isolate faults.

• For official installation guides, power calculation worksheets, and redundancy wiring diagrams, always refer to the documentation available at the product link: FOXBORO P0928AY. Installation must comply with electrical codes and be performed by qualified personnel.

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