Variable-frequency Drive (VFD) often has unreasonable shutdown during operation, which greatly affects our production line. When we investigated all possible causes, we still didn't find any problems. Later, after consulting the inverter manufacturer, it was found that it may be a power supply problem. It is recommended that we check it out first.
Because the basic principle of VFD is to provide voltage regulation and frequency regulation power supply for asynchronous motors to meet energy saving or process requirements, it has three parts: rectifier, DC and inverter. If the external voltage is unstable, the DC voltage will drop, making it impossible for the VFD part to continuously output the set voltage level, causing VFD protection to stop.
During the investigation, we monitored the input power of the VFD with a power quality analyzer for about half a month. It turns out that the quality of power supply does affect the normal operation of VFDs.
After monitoring for a while, it was found that the VFD suddenly stopped. Looking at the data recorded by the power quality analyzer, it is clear that there was a very serious voltage drop at the same time as the shutdown, which dropped by almost 80%. From this, we can determine that the shutdown is caused by voltage dips.
At the end of the article, several common reasons why VFDs may be shut down are introduced:
1. Whether the power supply voltage is normal, too high or too low will cause shutdown.
2. Regardless of whether the parameter setting is correct, in some cases, such as constant pressure water supply, when the target pressure is reached, the machine will automatically stop and then restart, which is normal.
3. Whether there are a large number of harmonics in the power supply, which need to be detected with a power quality analyzer or handheld oscilloscope.
4. VFD hardware failure. For example, hardware failures such as contactors.