The OV-BUS fault is caused by overvoltage on the DC busbar INTERNAL to the inverter. This can be caused by several reasons, but most of them are internal failures of the inverter.
Some of the most common causes for this alarm are:
- Power Board is broken
- Relays are damaged
- Connections between EMI board and Power board are not connected
- The OV BUS alarm can also occur due to a voltage difference between strings within the same MPPT. Sometimes an MPPT has two or four strings (depending on the model) and all strings connected to the same MPPT must have similar voltages. When there is a large variation between those strings, the alarm can be triggered.
Troubleshooting
*This applies for all 1P and 3P inverters*
- Make sure to get all basic pictures (nameplate, open wirebox, general installation and closeup of the alarm on the LCD)
- Get pictures of AC and DC voltages with the meter
- Make sure that the DC voltage is within range of the inverter’s specifications
- Check that correct grid standard is being used
- Get a short video showing the OV BUS alarm on the display and nameplate of the inverter
- Make sure to collect inverter’s firmware version (in case a firmware update might be needed in case the IGBT test is good)
- Try a restore settings (advanced info> Grid on/off> set to OFF> go back to advanced info menu>restore settings) ***if unit is a 2G “restore settings” will be on the regular settings menu***
- Fully power cycle the unit and set grid back to ON in the inverter’s menu.
- If alarm does not clear, instruct the tech to perform an IGBT Test and make sure the tech provides pictures of the test of each string
If the IGBT test results are normal, review with L2 the possibility of an update being needed.
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