XVR error reaction to F88XX

Hello,

A customer is testing various error reaction scenarios on his machine. The goal is to do everything possible to allow the NC to do a coordinated shutdown of the axes instead of the drive going into its own independent error reaction.

Since the machine will be installed in region with frequent brownouts, he is testing what happens if mains power is disconnected from the XVR while the machine is running. What he sees is F8812 on the XVR and F8064 on the drives. I also get F8064 on my ctrlX DRIVE demo when I hit the estop, which cuts the 48V supply. So F8064 means the DC bus is nearly at 0V cannot supply current to the motor. 

On the machine, one of the axes is a large drum with a high inertia. We expect the regen energy when decelerating should keep the DC bus energized and allow the coordinated stop, but instead the axis gets F8064 and is coasting (torque free). One question I have - how does the XVR react to F88XX? According to this screen in Drive Engineering the reaction is "immediate power off". Does this mean the bleeder resistor is used to actively discharge the DC bus? Or would the bleeder only turn on if the DC bus gets too high, or if commanded to turn on by the power supply control word S-0-1720.0.1 bit 10?

Tomorrow I will have the opportunity to remote connect with the machine and scope the power supply control word, status word, DC bus voltage etc. to get a better idea what is going on, but for now I'm trying to determine what is the expected reaction and if there are any parameters to influence it.

Best regards,

Brian