The Hollysys LK series is a large-scale programmable logic controller engineered specifically for critical infrastructure and process automation applications where high reliability and continuous operation are paramount. Its defining characteristic is a dual-backplane redundant architecture that provides comprehensive fault tolerance across all major system components, including power supply, CPU controller, Ethernet communication, and PROFIBUS-DP fieldbus network. The two controllers are mounted on separate backplanes (A series and B series), synchronizing data via high-speed backplane bus without dedicated synchronization modules. In the event of a primary component failure, the system executes a seamless switchover with a redundancy switching time of no more than 130 milliseconds. This robust design ensures that a single point of failure does not lead to system downtime, making the LK series an ideal core for applications in subway systems, water treatment, power generation, and continuous process control.

Performance is delivered by a high-speed industrial-grade processor operating at up to 667 MHz, achieving instruction execution speeds of 20 nanoseconds for bit and fixed-point operations and 28 nanoseconds for floating-point operations. The controller provides 32 MB of program storage (equally divided between system and user space) and 512 KB of MRAM for power-loss data protection. The system supports a minimum task scheduling time of less than 100 microseconds and a loop response time of less than 200 milliseconds, ensuring deterministic and responsive control for even the most demanding high-speed applications. All modules are designed for hot-swappable replacement, significantly reducing maintenance time and minimizing operational disruptions.

Communication is a cornerstone of the LK platform's open and integrated design. Each CPU integrates one Ethernet port, two serial ports, and a redundant PROFIBUS-DP interface. The Ethernet port natively supports Modbus TCP and OPC, while the serial ports handle Modbus RTU and user-defined free protocols. For systems requiring expanded communication capabilities, optional modules can be added to support additional serial ports, Ethernet interfaces, and PROFIBUS-DP master/slave configurations. The system also provides station-to-station communication functionality, enabling seamless data exchange across distributed control stations in industries such as water conservancy, power generation, and municipal transportation. The system has achieved Wurldtech's Achilles international certification, validating its robust defense against tens of thousands of known and zero-day network vulnerabilities.

Scalability is another key strength of the LK series. A single PROFIBUS-DP network can support up to 124 I/O slave stations, and the total system capacity exceeds 10,000 I/O points. The comprehensive module portfolio includes digital and analog I/O, temperature measurement (TC/RTD), pulse counting, and specialized communication modules. The system supports three-proofing treatment (moisture proofing, salt spray proofing, and fungus proofing) according to GB2423 standards, ensuring reliable operation in harsh industrial environments. Engineering and programming are accomplished via the AutoThink software suite, which is fully compliant with the IEC 61131-3 international standard and supports Ladder Diagram (LD) and Function Block Diagram (FBD) programming. The LKS variant within the LK family is SIL2-certified by TÜV SÜD according to IEC61508 and IEC61511, achieving 99.99% safety loop availability and over 90% diagnostic coverage, making it suitable for deployment in safety-instrumented systems (SIS) including Emergency Shutdown Systems (ESD), Process Shutdown Systems (PSD), and Burner Management Systems (BMS).

Technical Specifications