4256A84G03 / 3A99159G03 Emerson Ovation WDPF DCS 3rd-Gen High Reliability Isolated Relay Output Module
4256A84G03 is the legacy Westinghouse drawing part number; 3A99159G03 is Emerson’s official aftermarket interchange spare part number. The two part numbers correspond to the identical third-generation high-reliability isolated relay output module, fully plug-and-play backward compatible with early revisions 4256A84G01 / 4256A84G02. It matches 4256A25 series MRC main remote control boards and 4256A26 remote expansion boards for Ovation remote I/O rack assembly, no system logic program, parameter or configuration modification required during card replacement.
Description
This module converts digital control commands transmitted from the MRC master controller into mechanical contact switching signals via fully isolated industrial sealed relays, to drive field solenoid valves, alarm horns, panel indicator lights, small auxiliary contactors, safety interlock loops and light-load field actuators. Each channel adopts dual-stage isolation architecture: optocoupler front isolation + signal relay back isolation, completely eliminating cross-channel signal crosstalk, ground loop coupling noise and external electromagnetic interference. Embedded full-coverage intelligent fault diagnosis logic can detect relay contact adhesion, output circuit open-circuit, short-circuit overload, inductive load back-EMF abnormal status, and upload real-time single-channel fault alarm signals to the DCS host through MRC Link differential bus.
Compared with G01 and G02 previous generations, G03 revision upgrades long-life hermetically sealed industrial relays with superior mechanical & electrical switching endurance; equips three-stage composite surge absorption and high-efficiency freewheeling protection circuits for coil-type inductive loads; optimizes multi-layer EMI suppression PCB layout to adapt to heavy industrial sites with intense electromagnetic radiation; adds full-cycle relay contact health monitoring function and accelerates fault state feedback response speed, ideal for high-frequency switching and high-safety interlock control applications in thermal power, petrochemical and metallurgy industries.
The circuit board adopts multi-layer high-temperature resistant FR-4 industrial PCB with 360° full-surround electromagnetic shielding structure. Every independent relay output channel achieves 1000V AC/DC reinforced galvanic isolation between field wiring terminals and internal logic circuits, effectively isolating lightning surge impact, high-frequency radiation and back electromotive force interference generated by high-voltage switchgears, large rotating machinery and frequency converters. All finished products pass full-lifecycle strict factory reliability validation, including 72-hour high-low temperature cyclic aging test, full-channel relay pull-in/release precision calibration, long-duration full-load MRC Link bus continuous burn-in test, and comprehensive simulation tests of relay contact wear, wiring open-circuit & short-circuit faults.
It supports single-slot hot-swappable online replacement without powering down the entire remote I/O station. Each output channel integrates multi-layer comprehensive hardware protection: surge suppression, instantaneous overcurrent cut-off, reverse polarity prevention, inductive load back-EMF absorption, overload self-locking lockout, preventing permanent module damage caused by on-site wiring misoperation or load short-circuit failure. Independent LED diagnostic indicators separately display power supply status, MRC bus communication link state, real-time relay on/off output status and single-channel loop fault alarm information, supporting fast on-site inspection and troubleshooting.
Technical Specifications
PCB Substrate: Multi-layer high heat-resistant FR-4 industrial printed circuit board
Operating Temperature Range: -25℃ ~ +75℃
Storage Humidity: 5% ~ 90% RH, non-condensing
EMC Compliance: Industrial Class II, CE certified, compliant with EN 61000 series anti-interference standards
Communication Bus: Dedicated MRC Link differential bus for Ovation remote I/O racks
Channel Isolation Withstand Voltage: 1000V AC/DC galvanic isolation per independent relay output channel
Output Type: Sealed industrial mechanical isolated relay contact output, compatible with AC/DC light-load field interlock equipment drive
On-board Integrated Protections: Surge suppression, overcurrent protection, reverse polarity prevention, inductive load freewheeling protection, overload self-locking lockout
Installation Mode: Single-slot hot-swappable plug-in module matched with standard Ovation DCS rack backplane
Quality Warranty: Genuine original Emerson/Westinghouse product, equipped with independent factory inspection test report, 12-month official warranty
Application Fields
Medium and super-large thermal power plant Ovation WDPF distributed control systems, petrochemical plant process regulating valve interlock control cabinets, metallurgical smelting furnace auxiliary equipment logic drive stations, municipal waste incineration plant flue gas baffle and safety alarm control systems, pulp & paper factory production line auxiliary actuator control racks, multi-rack redundant central control rooms of traditional heavy industry, high-safety interlock and auxiliary equipment logic automation platforms for energy & chemical continuous production lines, centralized DCS monitoring and control systems for large-scale distributed energy storage power stations
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