Robust Operation of Dayu Instruments in Industrial Settings: Solutions for VFD Interference
In industrial settings, ultrasonic instruments are widely used for monitoring parameters such as level and flow, thanks to their non-contact and high-precision measurement advantages. However, with the increasing prevalence of variable frequency drives (VFDs) in motor control, their electromagnetic interference with ultrasonic instruments has become increasingly prominent. To ensure the robust operation of ultrasonic instruments in industrial environments, we hereby propose the following solutions.
Ultrasonic instruments, such as ultrasonic level meters, ultrasonic level difference meters, ultrasonic open-channel flow meters, ultrasonic flow meters (for measuring liquid flow in pipes), and ultrasonic sludge level meters, play a crucial role in industrial settings. However, when these instruments coexist with VFDs, they may be subject to electromagnetic interference from the VFDs, leading to unstable measurement data or increased errors.
To address the interference issues caused by VFDs on ultrasonic instruments, we propose the following solutions:
1. For electromagnetic interference transmitted through the air, we recommend increasing the distance between the VFD and the ultrasonic instrument, or using a metal instrument enclosure to shield the ultrasonic instrument, ensuring the enclosure is reliably grounded. Additionally, the VFD can also be shielded, but attention should be paid to its heat dissipation.
2. For interference conducted through signal lines, we emphasize that the instrument itself must be grounded with a grounding resistance of ≤4 ohms. Furthermore, a signal isolator should be installed at the instrument's output signal terminal to isolate interference from the VFD or PLC, while also preventing the instrument's interference from being conducted to other devices.
3. For interference from the power lines, we recommend installing an isolation transformer between the power line and the instrument, or adding EMI filters to the VFD's input and output circuits. At the same time, the VFD should be grounded separately, and all ground wires must be individually grounded, not interconnected.
In the sewage pump station project at Guangzhou Asian Games Village, we successfully applied the aforementioned solutions to resolve the interference issues of VFDs on ultrasonic level meters and ultrasonic level difference meters. By installing filters, isolation transformers, and signal isolators, and ensuring the instruments were individually grounded, we ensured the stable operation of the ultrasonic instruments when the VFDs were in operation.
We are well aware that in industrial settings, every detail matters for production safety and efficiency. Therefore, we will continue to dedicate ourselves to the research, development, and innovation of ultrasonic instrument technology, contributing to the automation and intelligent development of industrial sites. At the same time, we look forward to working hand in hand with more partners to jointly address challenges and create a better future.