A: The UPS displays the alarm 'Rectifier fail‑Set/REC Soft Start Fail‑SET' on the screen and the rectifier fails to start normally. How to troubleshoot this fault? 

When the UPS of this series shows the alarm 'Rectifier fail‑Set/REC Soft Start Fail‑SET' on its screen, please carry out troubleshooting in accordance with the following steps:

1. Re-insert the Power Module into the cabinet again.  
2. Remove the cover of the faulty UPS, and Locate the rectifier power board 17001-02401 (There are three pieces of this board in the Power Module), and test the IGBT according to the requirements . If it is damaged, replace the board and check the result.  
3. Locate the input SCR board 17001-05097 , and test the fuses and SCR according to the requirements . If it is damaged, replace the board and check the result.
NOTE: These alarms cause most probably because of the INPUT and RECTIFIER power board.
4. Locate the inverter power board 17001-02549 (There are three pieces of this board in the Power Module), and test the IGBTs according to the requirements. If it is damaged, replace the board and check the result.
5. Locate the inverter busbar board 17001-02458, and test the fuses according to the requirements. If it is damaged, replace the board and check the result.
6. Check the rectifier busbar board 17001-02385 using the same method as step 5；If it is damaged,replace the board and check the result.
Alternatively, check whether a bus voltage value（Searching Way：MODULE-INFO-BUS） is displayed for this module on the UPS screen；if the voltage is displayed and within the normal range, it indicates the unit is functioning properly
7. Replace the control board 17001-02348.