The PM891 is a high-performance redundant central processing unit from ABB that is part of the System 800xA distributed control system. Here are the details:

Hardware configuration: is a single unit, equipped with a power supply, CPU board and unit terminal. The interior contains a microprocessor, RAM memory, real-time clock, LED indicator, INIT button and secure digital interface. There are two RJ45 Ethernet ports (CN1, CN2) for connecting to the control network, and one RJ45 serial port (COM4), which is isolated and used for configuration tools.

Functional features:

Redundancy design: Supports CPU redundancy to improve system availability. When the primary CPU fails, the standby CPU can quickly take over the work, ensuring continuous system operation, reducing downtime, and improving productivity.

Communication extension: The Communication Extension Bus (CEX-Bus) is used to extend the onboard communication port through the communication interface unit, which can use redundant communication interfaces. The CEX-Bus interconnect unit BC810 divides the CEX-Bus into separate segments to improve its availability. The optical module bus can connect seven sets of S800 I/O units, each containing up to 12 units. Each PM891 has a unique Ethernet address that provides a hardware identity for the device.

Applications: Suitable for a variety of industrial automation applications, especially oil and gas, power generation, chemical processing and other complex control and automation applications requiring high reliability, high availability and high performance. Various machines and equipment can be controlled in factory automation; Real-time monitoring and control of processes in chemical, pharmaceutical and food industries in process control; In the field of energy management, it can be used to monitor and control the production, transmission and consumption of electricity, water and gas.

Here are some models related to the PM891:

PM861: The same ABB AC800M series, support processor unit redundancy, can be the same as PM891, in the controller contains two processor units, to achieve the hot standby function, when the main unit fails, the standby unit can take over the work in less than 10ms time, to ensure the stable operation of the system.

PM864: Also a controller model in the AC800M series, it supports processor redundancy, has two processor units, and can be used as the primary controller or standby controller in the system. It has certain similarities with the PM891 in function features and application scenarios, and is often used in industrial applications that require high reliability of the control system.

PM866: It is part of the AC800M series and supports redundancy, similar to the PM891, with two built-in IEEE802.3 Ethernet channels for control network connectivity, and provides a Communication extension bus (CEX bus) that can connect multiple extension modules to meet the connection needs of different fieldbuses and I/O systems.

PM891K01: Is a specific version of the PM891 model, such as ABB's 3BSE053241R1 product, its packaging includes PM891 CPU module, TB850 (CEX bus terminal), TB853 (RCU control link terminal), usually used in specific industrial automation control scenarios. It is closely related to PM891 in function and application.