Restart only disable-then-enable the faulted rail to see whether it can recover from the previous fault. Restart is only applied on the faulted rails. The device repeats this until the restart is exhausted.
Re-sequence is applied on the fault rails plus its fault shutdown slaves. All rails designated as fault shutdown slaves of the faulted rail are disabled based on its own shutdown sequence first. Then the device tries to sequence on all rails to see whether they can recover from the previous fault.
After the number of restart is exhausted, re-sequence takes place. The maximum number of re-sequence is configured under the Global Configuration tab → Misc Config.
Figure 21 shows a flow chart of restart and re-sequence.
A UV fault can be only set to restart once because the UV fault cannot be detected until the unit has reached regulation; otherwise, the rail would never turn on initially. This means every UV condition is a unique event as the rail would have been regulating before it occurs.
To handle the condition where the rail fails to start after a UV condition, TON_MAX_FAULT_LIMIT should be used (it is listed as Max Turn On beneath the Turn On Delay setting in the GUI). This sets the maximum amount of time allowed before the rail is expected to be within regulation. If this is exceeded, then a fault is declared and a separate fault response handles this condition (with a different name, Time On Max). Time On Max can be set to trigger multiple times.
For more FAQ please check the following document.
UCD90xxx Family Frequently Asked Questions and Answers
UCD9090 UCD9090A UCD90120 UCD90120A UCD90124 UCD90124A UCD90160 UCD90160A UCD90320 UCD90320U