Cause : IGBT Phase-U fault comes when there's an issue related to IGBT Phase-U in the power stage of the drive, specifically affecting a particular phase's voltage.

OUt1 indicate a short is detected on the load side when the voltage across the IGBT of Phase-U collector to emitter is excessive or high current is detected through an IGBT.

1. Physically inspect the IGBT modules in the drive. Look for signs of damage such as burn marks, melted solder joints, or physical cracks. If any modules appear damaged, they may need to be replaced.
2. Inspect the gate drive circuitry that controls the IGBTs. Ensure that the gate signals are being properly generated and delivered to the IGBT modules. Problems with the gate drive circuitry can lead to faults in the IGBTs.
3. Check the power supply supplying the drive for proper voltage and stability. Fluctuations or abnormalities in the power supply can affect the operation of the IGBTs.