Modular PLCs

What are Modular PLCs?

Modular PLCs (Programmable Logic Controllers) are rack-based industrial computers designed for complex automation tasks that require high I/O counts, advanced processing power, and hardware flexibility. Unlike compact PLCs, modular systems allow engineers to customize the controller by selecting specific components (CPU modules, Power Supplies, Digital/Analog I/O, and Specialized Communication cards) and Installing them into a backplane or chassis. This architecture enables easy expansion; as your facility grows, you simply add more modules to the existing rack rather than replacing the entire controller.

Main Manufacturers

Palm Parts Solution stocks a comprehensive inventory of modular PLC components from the industry’s leading brands:

• Allen-Bradley: Including the high-performance ControlLogix and the versatile CompactLogix platforms.
• Siemens: Featuring the SIMATIC S7-1500 for advanced applications and the legacy S7-300/S7-400 series.
• GE Fanuc: Specializing in the PACSystems RX3i and legacy Series 90-30 and 90-70 parts.
• Mitsubishi Electric: Units from the MELSEC iQ-R and Q Series for high-speed manufacturing.
• Schneider Electric: Focusing on the Modicon M580 ePAC and M340 modular ranges.

Typical Applications

Modular PLCs are the preferred choice for large-scale industrial operations where downtime must be minimized and data throughput is high. Typical applications include:

• Automotive Assembly: Managing synchronized robotics and multi-axis motion control via Kinetix or SINAMICS drives.
• Process Industries: Oil & Gas, chemical processing, and water treatment where high-density analog I/O and PID loops are required.
• Material Handling: Large-scale warehousing systems utilizing extensive EtherNet/IP or PROFINET networks.
• Power Plants: Utilizing redundant modular CPUs to ensure 24/7 system availability.

Selection Guide

When selecting a modular PLC, technical specifications must alignment with system requirements:

1. I/O Density: Determine the total point count and whether you require isolated or non-isolated modules.
2. Processing Speed: Evaluate the Scan Time requirements; high-speed logic often requires premium CPUs like the ControlLogix 5580.
3. Communication Requirements: Ensure the CPU or communication modules support your existing fieldbus (e.g., EtherCAT, DeviceNet, or CC-Link).
4. Environment: Check for conformal coating requirements if the PLC will be exposed to corrosive or humid environments.
5. Migration Paths: If replacing an obsolete GE Fanuc 90-30, consider if a modern RX3i CPU can utilize the existing backplane to save on rewiring costs.