25 hp (18.5 kW) high performance variable frequency drive, three phase 240V, 420V, 480V for selection, IP20 enclosure.

Specification:

Tips: Variable frequency drive undervoltage
The undervoltage is a problem that we often encounter in using VFD. It is mainly because of the main circuit voltage is too low (220V series below 200V, 380V series below 400V). The main reason: One circuit of rectifier bridge damage or one circuit of SCR does not work correctly, all these can lead to undervoltage. Moreover, the main circuit contactor damage resulting DC bus has voltage loss in the charge resistance may lead to undervoltage. And the voltage detection circuit failure may also cause undervoltage problem.
For example, a 25hp VFD displays "Uu" after power on. Check the rectifier bridge charge resistance and find no problem, but haven't heard a sound of the contact action after power on. Because this VFD charging circuit doesn't use SCR but depend on the contactor attracting to complete the charging process, so that the failure may be caused by the contactor, control circuit or power supply. Remove the contactor, and individually connect 24V DC, the contactor is working properly. And then check the 24V DC power supply and find the voltage regulator tube is damaged. After replacing it, VFD is working properly.