The XXX project uses a new 6 kVA inverter. After the inverter is installed, the inverter indicator blinks for tens of seconds and then the inverter transfers to bypass mode. The Fault indicator is on in red, and alarm tones are generated. Currently, the inverter is powered by batteries. The battery input voltage is 48.8 V.
1. The DC fuse is broken. If the UPS can be completely shut down, use a multimeter to measure resistance to check for open circuits. If the UPS cannot shut down, use the DC voltage position of the multiplter to check for voltages. If there is a voltage, short circuits occur; if there is no voltage, no short circuit occurs. This is a common fault. If just the DC fuse is damaged, you need only to replace it.
2. Insulated gate bipolar transistors (IGBTs) are damaged: You can suspect that IGBTs are damaged only if the DC fuse open-circuits.
(1) If only a few IGBTs are damaged, visually inspect the shells for damage.
(2) Check the drive twisted pars and drive boards for burning damage.
3. The DC snubber resistor open-circuits.
The subcontractor starts the loads before starting the inverter. As a result, when the inverter is started, a huge transient current is generated, which burns the fuse.
Replace the fuse.