What are the best ways for Mitsubishi control box to control frequency converter
The inverter of Mitsubishi control box device can effectively ensure the safety and reliability of electrical equipment, stop the frequency conversion speed regulation of the power equipment such as fans, water pumps, etc., and reduce the starting current. The Mitsubishi control box mainly uses Mitsubishi PLC controller as the main control unit. There are many ways to control the inverter through the PLC controller, such as controlling the inverter through a switch signal, controlling the inverter through an analog quantity, or controlling through wireless communication. Inverters, etc., with so many varieties of Mitsubishi control boxes controlling the inverter, which one has the best effect?
That kind of Mitsubishi control box has a good effect on controlling the frequency converter
1. Controlled by expanding the storage method
The 485 communication module or communication board is required, and the expansion storage device is installed in the PLC controller of the Mitsubishi control box. The control function can be completed by connecting the two interfaces through the crystal head of the network cable. This control method is the simplest and the most basic control method among all methods. It does not need to stop complicated PLC programming. It is simple, convenient and fast.
The bad thing is that this method can only be used to control the frequency converter and cannot control other devices at the same time, and the number of controls will also be limited, so it is only suitable for small control projects.
2. Controlled by the switch signal of the Mitsubishi control box
After the PLC output point of the Mitsubishi control box is connected with the input end of the inverter to complete the control effect, the Mitsubishi PLC control program can control the start, stop and reset of the inverter. In addition, the Mitsubishi control box can also adjust variable speeds such as medium, high, and low speeds through the control of the PLC controller to the inverter. However, the frequency converter is controlled by the switch signal, and the frequency conversion speed cannot be adjusted precisely, because the speed adjustment curve is not a continuous and smooth curve. Therefore, the accuracy of conditioning is not as good as the control method of expanding the storage.
3. adopt bus control mode
The communication device can be installed in the frequency converter, and the field bus option can be used to connect the corresponding communication module of the PLC of the Mitsubishi control box to complete the bus connection. This method can control most high-quality inverters, and can reach the remote, high-speed inverter control, and the PLC programming is also relatively simple, and the stability is good. But the economic benefits are relatively high.
4. Using RS-485 Modbus-RTU communication control mode
The PLC controller stops communicating with the frequency converter via the RS-485 Modbus-RTU communication protocol to complete the control function. Compared to only using RS-485 terminals, Modbus-RTU communication control mode is a bit simpler, but also compared to the expansion memory control mode, the amount of PLC program programming of Modbus-RTU protocol is still relatively large.
5. Adopt RS-484 communication control method
Need to stop RS serial instruction programming via PLC. RS-484 communication control mode only requires simple hardware to stop, and has low economic benefits. The number of inverters controlled is also large, which can control up to 32 units.
Compared with the simple programming of the extended memory control mode, the programming of the RS-484 communication control mode is very complicated. A lot of programming work needs to be stopped, and professional PLC programming technicians are required to stop it. Regardless of the length of the programming, the amount of programming and the ease of programming, the RS-484 communication control method is inferior to the extended memory control method.
6. through the Mitsubishi control box imitating quantity signal control
Configure the analog input and output hybrid module for the Mitsubishi control box to complete the control of the inverter. This control method is relatively simple for PLC programming requests, and the speed regulation curve of the control inverter is also relatively smooth and continuous, so it can effectively ensure the stability of the Mitsubishi control box.
However, the use of imitated signals to control the inverter also has great disadvantages. For example, in a control project with a large amount of engineering, the control cable is longer. During the output of the module voltage line number, the line will produce a large voltage drop, which will affect the system. Stability and reliability. And if you need to control a pair of inverters, you need to imitate the quantity control module as quickly as possible. Relative to the expansion memory control method, the cost is about 6 times that of it, so the economic benefits are higher.
In general, each control method has its own advantages and disadvantages, and it can be selected based on its own control needs, the size of the engineering quantity, and the control effect and economy of the engineering needs. Regarding ordinary small-scale automation control projects, an expanded memory control method that is relatively inexpensive, easy to learn, and simple to program can be used. Compared with the large-scale optional fieldbus control method, this method is stable, simple and convenient, and relatively expensive. Other control methods also have their own advantages, so they can be selected based on practical control needs.