OU
Overvoltage in DC bus
Lenze · SM29_05 Service Bulletin
What does OU mean?
The DC bus voltage is higher than the value set in C0173, primarily caused by excessively high braking energy during deceleration. Sustained overvoltage can damage the drive's DC bus components.
Source: Lenze SM29_05 Service Bulletin
Open Manual (Page 326)