1.PLC Control via Digital (On/Off) Signals

Connect the output and COM terminals of PLC (MR or MT type) directly to the inverter terminals such as STF (Forward Run), RH (High Speed), RM (Medium Speed), RL (Low Speed), and SG (Common Input). The PLC can control the inverter’s start, stop, and reset through programming. Multi-speed operation is achieved by different combinations of high/medium/low speed terminals. However, since control relies on discrete digital signals, the speed curve is not continuous or smooth, and precise speed regulation cannot be realized.

2. PLC Control via Analog Signals Hardware

FX1N/FX2N PLC with FX1N-1DA-BD analog output board, FX0N-3A analog I/O module, FX2N-2DA (2-channel output), or FX2N-4DA (4-channel output) module.

Advantages: Simple and convenient PLC programming, smooth and continuous speed curve, stable operation.

Disadvantages: In large-scale production lines with long control cables, especially when the DA module outputs voltage signals, significant voltage drop occurs along the line, reducing system stability and reliability.

3. PLC Control via RS-485 Communication (Non-protocol)

The most widely used method. The PLC uses RS serial communication instructions for programming.

Advantages: Simple hardware, lowest cost, can control up to 32 inverters.

Disadvantages: Heavy programming workload.

4.PLC Control via RS-485 Modbus-RTU Protocol

Mitsubishi new F700 series inverters communicate with PLC via RS-485 terminals using the Modbus-RTU protocol.

Advantages: Easier and more convenient PLC programming than non-protocol RS-485.

Disadvantages: Still relatively heavy programming workload.

5.PLC Control via Fieldbus

Mitsubishi inverters support various built-in communication options: FR-A5NC for CC-Link, FR-A5AP(A) for Profibus DP, FR-A5ND for DeviceNet, etc. Mitsubishi FX series PLCs have corresponding interface modules for connection.

Advantages: High speed, long communication distance, high efficiency, stable operation, simple programming, supports a large number of inverters.

Disadvantages: Relatively high cost.

6.Control via Extended Memory

Advantages:Low cost, easy to learn and use, reliable performance.

Disadvantages: Only suitable for systems with no more than 8 inverters.