Product Overview

The FX3U-128MR/ES-A is the flagship high-capacity main unit within the Mitsubishi MELSEC FX3U series. As the third generation of Mitsubishi Electric's compact PLC family, the FX3U is designed to handle complex automation tasks that require high-speed processing and extensive I/O density.

With a total of 128 integrated I/O (64 inputs and 64 relay outputs), this unit provides a massive footprint in a single chassis, making it the ideal choice for centralized control in large-scale machinery, packaging lines, and textile equipment. The FX3U-128MR/ES-A is globally compatible, featuring a wide-range AC power supply and high-speed execution speeds that rival many larger modular PLCs, all while maintaining the space-saving benefits of a compact controller.

Technical Configuration

The FX3U-128MR/ES-A is engineered for high-end performance and system scalability:

• High-Speed Processing: Features an execution speed of 0.065 $\mu$s per basic instruction, allowing for rapid response in high-cycle applications.

• Expansion Capability: While it starts with 128 I/O, the unit can be expanded up to 256 local I/O points (or 384 points with remote I/O) using FX series expansion blocks.

• Integrated High-Speed Counters: Supports up to 8 channels of high-speed pulse counting (up to 100 kHz), essential for rotary encoders and position sensing.

• Dual Bus Architecture: Utilizes both a high-speed communication bus and an expansion bus, allowing for the simultaneous use of analog, networking (CC-Link, Ethernet), and positioning modules.

• Large Memory Capacity: Equipped with 64,000 steps of internal program memory, providing ample space for complex logic and extensive data registers.

Technical Specifications

Technical FAQs

What is the difference between the "MR" and "MT" versions?

The MR version (like this unit) features Relay outputs, which are versatile for switching both AC and DC loads and provide high current capacity. The MT version uses Transistor outputs, which are required for high-frequency switching and pulse-train output for servo/stepper motor control.

Can I use this PLC in both 110 V and 220 V environments?

Yes. The "ES-A" designation indicates a global power supply compatible with a range of 100–240 V AC, making it suitable for international export and various regional power standards.

Does this unit support battery-less operation?

The FX3U uses a battery to maintain the program and retentive data (registers) during power-off. While the program can be stored in optional Flash memory, a battery is required to keep the real-time clock and data values active.

Engineering & Installation Guide

Wiring and Terminal Safety

The FX3U-128MR/ES-A uses standard screw terminals. Given the high I/O density, ensure that wiring is neatly organized using cable ducts. For the 64 relay outputs, verify that the combined current does not exceed the unit's thermal rating. If switching inductive loads (solenoids, contactors), it is highly recommended to install surge suppressors (for AC) or freewheeling diodes (for DC) to protect the internal relay contacts from premature wear.

System Expansion

When expanding the 128-point base unit, pay close attention to the 5 V DC bus current consumption. Each expansion block draws power from the main unit; if the total consumption exceeds the FX3U's internal power supply capacity, an additional regulated power supply or an "expansion power supply unit" will be required.

Heat Dissipation and Mounting

Due to its length (350 mm) and high I/O count, this unit can generate significant heat during full-load operation. Always mount the PLC horizontally on a 35 mm DIN rail and maintain at least 50 mm of clearance above and below the unit for natural convection cooling. Avoid installing the PLC directly above heat-generating components like large frequency drives or transformers.