Description
I. Basic Information
Model: PM861AK02ABB Part No.: 3BSE018160R1Origin: SwitzerlandPlatform: ABB AC 800M DCS, System 800xA Industrial Automation PlatformProduct Type: Complete 1:1 hot redundant processor unit set, including 2×PM861A CPU modules, 2×TP830 baseplates, RCU-Link redundant synchronization cable, CEX-Bus extension cable and bus terminators. It serves as the core main control unit of distributed control systems, realizing closed-loop regulation, sequence control, interlock logic operation, I/O data scheduling and multi-system communication. The primary and standby CPUs achieve bumpless millisecond-level switchover to avoid unplanned shutdown caused by single-point hardware faults, applicable to power, chemical, water treatment and other high-reliability industrial scenarios, and supports SIL2/SIL3 functional safety configuration.
II. Hardware Architecture
1. Dual Redundant Main Control Unit
Equipped with two independent 48MHz 32-bit RISC processors, each with 16MB RAM and on-board flash memory for firmware storage. The built-in backup lithium battery retains process variables and configuration data after power failure. Primary and standby controllers synchronize user programs, real-time variables and fault records in real time via dedicated RCU-Link cable. Faulty modules support hot-swap replacement without process shutdown. The minimum task scan cycle reaches 1ms, and the redundant configuration supports up to 84 S800 I/O modules to realize large-scale process signal acquisition and control output.
2. Multi-channel Galvanically Isolated Communication Unit
Each PM861A integrates 2×10Mbps RJ45 Ethernet ports (supporting MMS, Modbus TCP), 1×RS232 general serial port (Modbus RTU), 1×isolated RS232 service port for programming and fault diagnosis. The CEX-Bus field bus realizes high-speed data interaction with local and remote S800 I/O stations, equipped with CRC data check and heartbeat fault detection mechanisms to monitor I/O loop abnormalities in real time.
3. Hardware Self-diagnosis & Status Indication Unit
Front-panel LED indicators display running, fault, redundant synchronization and bus communication status for rapid fault location. Fault codes and timestamped event logs are latched and readable via Control Builder M software. The INIT button supports controller initialization, redundant pairing reset and factory reset.
4. Power Supply & EMC Protection Unit
24VDC backplane power supply with reverse polarity, surge, ESD and short-circuit protection. Conformal coated PCB ensures stable operation under harsh electromagnetic interference in control cabinets.
5. DIN Rail Mount Structure
Standard DIN35 rail installation, fanless passive heat dissipation design, metal reinforced front panel to reduce dust and high-temperature failure risks.
III. Mounting Specifications
- Power Supply: 24VDC (19.2~26.4VDC), single CPU power consumption ≤5W
- Processor: 32-bit RISC @ 48MHz, 16MB RAM
- Max I/O Capacity: 84 S800 I/O modules under redundant configuration
- Dielectric Withstand Voltage: 500VAC between communication port and ground
- Single Module Dimension: 98mm×186mm×130mm, Net Weight: 0.39kg
- Protection Class: IP20 (for indoor closed dust-proof cabinets only)
- Supporting Tools: Control Builder M, insulation resistance tester, anti-static wristband
IV. Supporting System
1. Hardware Matching
AC800M control rack, S800 series I/O modules, 24VDC redundant power supply, field transmitters and field actuators.
2. Configuration Software
Control Builder M for logic programming, hardware configuration, redundant parameter setting, firmware upgrade and fault log export.
3. Upper System Connection
System 800xA, DCS/SIS, SCADA platforms realize remote centralized monitoring, parameter archiving and accident traceability.
4. Typical Industries
Thermal power, petrochemical, municipal water treatment, metallurgy, pharmaceutical, food processing and oil & gas station automation.
V. Product Features
- Factory integrated 1:1 hot redundant architecture ensures bumpless switchover and on-line maintenance of faulty modules to maximize system continuous operation reliability.
- Multi-protocol flexible networking and CEX-Bus distributed I/O expansion support system capacity expansion and technical renovation.
- Full-loop hardware self-diagnosis with timestamped fault event storage facilitates safety audit and accident analysis.
- Compliant with IEC 61131-3 standard programming languages, supporting on-line incremental program download without interrupting field control.
- Wide-temperature rugged industrial design with excellent EMC performance, certified by CE, UL, ATEX, applicable to harsh industrial environments.
- Downward compatible with AC800M series hardware for rapid spare replacement and commissioning.
VI. Working Principle
After power-on sequential startup, the primary and standby CPUs complete hardware self-test, load firmware and user programs, and synchronize all operating data via RCU-Link cable. The primary controller executes cyclic control logic, collects field signals via CEX-Bus and issues control commands. Once the primary unit fails, the standby controller takes over all control tasks within milliseconds with undisturbed output. Fault information is uploaded to the upper monitoring system, and the replaced spare CPU automatically completes data synchronization to rejoin the redundant system.
VII. Application Scenarios
- Auxiliary control system renovation and new construction for thermal power plants.
- Process DCS deployment for petrochemical and pharmaceutical hazardous production plants.
- Municipal water supply and wastewater treatment automation projects.
- Production line control for metallurgy, paper and food industries.
- Preventive spare parts reserve and emergency hardware replacement for industrial automation systems.
