Overvoltage on DC bus is usually related to deceleration issues or "on the fly" starting which may be happening if you have a "blink" in the supply line.
Whatever the reason for the "blink" it may be that you need to check out settings for how a power failure/power resume is handled.
If it is trying to restart on the fly and parameters associated with that task are not set correctly, the still spinning load will generate power and dump it into the drive the drive needs to correctly determine current motor speed and adjust it's output accordingly when it does come back on line - this is what is causing the overvoltage on the bus. You get similar problem if you set deceleration time too short.
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