Three ways to connect PLC and inverter

In the field of industrial automation control, the combination of PLC (Programmable Logic Controller) and frequency converter is widely used. There are three main ways to connect them:

1. Analog connection

Analog connection is a common connection method. PLC outputs analog signals to the inverter through analog output modules, such as 0-10V or 4-20mA voltage or current signals, to control the output frequency of the inverter. The advantages of this connection method are simple, intuitive and easy to implement.

For you, if you do not have particularly high requirements for the accuracy of the control system and the field equipment has strong anti-interference ability to the signal, analog connection is a good choice. For example, in some small production equipment, analog connection can meet basic speed regulation needs. However, analog signals are easily interfered by the outside world, which may lead to reduced control accuracy. In addition, the cost of analog modules is relatively high, and the signal will attenuate during long-distance transmission.

2. Digital connection

Digital connection mainly controls the start and stop, forward and reverse functions of the inverter through the digital output points of the PLC, and reads the operating status and fault information of the inverter through the digital input points. The advantages of this connection method are strong anti-interference ability and stable and reliable signals.

In practical applications, digital quantity connection is suitable for occasions where the control accuracy is not high but the system stability is high. For example, in some harsh industrial environments, digital quantity connection can ensure the normal operation of the system. However, digital quantity connection can only realize simple control functions and cannot realize continuous adjustment of the inverter output frequency.

3. Communication connection

Communication connection is currently a more advanced connection method. PLC and inverter exchange data through communication protocols, such as Modbus, Profibus, Ethernet, etc. This connection method can realize comprehensive control of the inverter, including frequency adjustment, parameter setting, status monitoring, etc.

For you, if you need to centrally control multiple inverters, or have high requirements for the intelligence of the control system, communication connection is the best choice. Communication connection can greatly reduce wiring costs and improve system reliability and maintainability. At the same time, through communication protocols, it can also be integrated with other devices to build a more complex automation control system. However, communication connection requires certain programming and debugging techniques, and has high requirements for operators.

In summary, the three connection methods of PLC and inverter have their own advantages and disadvantages. In actual applications, you can choose the appropriate connection method according to specific control requirements and on-site conditions to achieve efficient and stable industrial automation control.