Description

ABB PM645B 3BSE010535R1

I. Basic Information

Model: PM645B, Part Number: 3BSE010535R1. It is a medium-sized redundant master CPU processor for ABB Advant OCS / AC800M DCS systems, serving as the core arithmetic spare part for legacy DCS cabinets in thermal power plants, chemical and papermaking industries. It supports dual hot redundant configuration for 24/7 non-stop continuous operation.

Product Positioning: Core computing unit of controller station responsible for centralized local S800 I/O signal acquisition, closed-loop PID calculation and interlock logic processing. It establishes network connection with upper operator stations and on-site UFC remote substations via dual PROFIBUS-DP plus Ethernet. Suffix codes R1/R2 denote different firmware revisions with identical hardware pin definition and mounting dimension for direct in-place replacement.

Brand: ABB Process Automation | Origin: Switzerland
Category: DCS Redundant CPU Processor Module
Compatibility: Advant OCS, AC800M DCS, S800 series I/O modules and UFC921A remote I/O substations
Mounting: Plug-in installation into standard rack slots; Overall dimension: 252×273×40mm; Net weight: approx.1.75kg; Full PCB triple-proof coating; Ingress Protection: IP20 (for installation inside sealed control cabinets)
Onboard Interfaces: Dual PROFIBUS-DP (DB9), dual RJ45 Ethernet ports, RS232 debugging serial port, power terminals and RUN/FAIL/COM status LED array

II. Technical Specifications

(1) Main Controller Calculation & Storage Parameters

Processor: 32-bit industrial RISC CPU with minimum control cycle of 1ms, applicable for high-precision closed-loop control of flow, pressure and temperature;
Memory: 256MB program Flash + 1GB DDR operating memory; programs and process parameters are permanently retained after power outage;
Programming Standard: Fully compliant with IEC61131-3 supporting five programming languages (ST/FBD/LD/SFC/IL); online download and debugging realized via Control Builder F configuration software.

(2) Communication Interface Parameters

Dual Isolated PROFIBUS-DP/V1: Two electrically isolated DP buses with auto-adaptive baud rate from 9.6k up to 12Mbps. One channel connects local S800 I/O while the other links UFC remote I/O substations; redundant bus design avoids system shutdown caused by single cable breakage.
Dual Redundant Industrial Ethernet: 10/100Mbps auto-adaptive; dual redundant network links to DCS servers and upper SCADA HMI.
RS232 Debug Port: Local serial interface connecting laptop for firmware upgrade, troubleshooting and program upload/download.

(3) Electrical & Environmental Specifications

Power Supply: 24VDC±10%, total rated power consumption ≤12W; onboard protection against overvoltage, reverse polarity and surge transient.
Operating Temperature: 0℃～+60℃ for continuous cabinet operation; Storage & transit temperature: -40℃～+85℃.
Ambient Condition: 5%~95% RH non-condensing; complies with IEC61000 EMC immunity standard to withstand VFD harmonics, dust and vapor corrosion in power plant environments.

PM645B 3BSE010535R1.jpg

III. Key Features

1:1 Dual Hot Redundancy with Bumpless Switchover

Two PM645B modules run in parallel as master and standby respectively. Instant bumpless switchover to standby CPU within milliseconds upon master failure to guarantee uninterrupted operation of critical process loops; this redundant architecture is standard configuration for boiler master control in thermal plants and reactor control in chemical industries.

Quadruple Link Redundancy via Dual DP + Dual Ethernet

All fieldbus and upper-level communication networks adopt redundant layout. Damage of single Ethernet or DP cable will not affect overall controller performance, an optimal upgrade solution for legacy renovation projects.

High-capacity Logic Processing for Centralized Multi-loop PID Regulation

Single CPU supports hundreds of PID loops for flow, liquid level and temperature plus thousands of digital interlock points, enabling centralized management of all on-site I/O within one rack for complete process units.

Full-range Self-diagnosis with Fault Message Upload

Built-in CPU self-check function triggers LED alarm for I/O open-circuit and communication abnormalities; fault information is transmitted to DCS HMI via Ethernet for rapid fault localization.

Seamless Compatibility for Retrofit Replacement of Legacy Advant Systems

Fully compatible with outdated ABB Advant OCS units; existing S800 I/O and field instrument wiring can be retained while obsolete legacy PM-series CPUs are directly replaced.

IV. Working Principle

Power-on Self-test: After 24VDC energization, the CPU runs self-inspection on processor, memory and all communication chips and loads pre-configured programs and PID parameters stored in Flash memory.
Cyclic Data Collection: Poll S800 I/O and UFC921A remote substations via PROFIBUS-DP to acquire field 4~20mA analog signals and valve status digital signals.
Logic Execution: Process interlock logics and multi-loop PID algorithms; output control commands via AO/DO channels to modulate regulating valves and switch field equipment.
Real-time Data Upload: Transmit real-time process data and alarm messages cyclically to upper DCS server via Ethernet and receive remote operator commands.
Redundancy Synchronization: Standby CPU synchronizes all operational data from master CPU in real time and takes full control instantly once master module fails.

V. Application Scenarios

(1) Master Control for Thermal Power Boiler & Steam Turbine (Primary Application)

Closed-loop regulation of boiler drum water level, furnace pressure and main steam temperature; interlock logic for forced/induced draft fans and coal mills; standard CPU for unit DCS master stations.

(2) DCS Main Controller for Petrochemical & Coal-Chemical Plants

Temperature & level control for distillation columns and chemical reactors, emergency shutoff interlock for tank farms and sequence control of compressor sets.

(3) Master Control for Papermaking & Metallurgical Production Lines

Centralized full-line tension control for paper machines, closed-loop rolling pressure regulation and furnace temperature interlock control for heating furnaces.

(4) Municipal Water Treatment & Waste-to-Energy Power Plants

PID control for aeration and chemical dosing in biochemical pools and interlock logic for pump unit groups.

Version Differentiation within Product Series

PM645B-3BSE010535R1: Standard version with dual DP + dual Ethernet, universal for thermal power and chemical industries.
PM645B-3BSE010535R2: Updated firmware version with expanded fiber-optic DP interface, dedicated for long-distance networking of large-scale industrial sites.