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What is the Over Braking Fault on Altivar 61 drive.

The ObF [Over Braking Fault] appears when the drive is in a run state and voltage on a DC bus is over the OBF level that represents 825V DC (a N4 version), When there is a voltage dip, the drive goes in the deceleration mode & if the motor is connect to high inertia load, it works in a Generator mode & trip on OBF fault. 

Most usual cases of OBF fault are: 
- Motor works in a Generator mode 
- The braking is too dynamic 

Both cases cause too much energy to dissipate in DC bus. 

To avoid that: 
- Increase the DEC [Deceleration ramp] as much as the application allows; 
- Activate the brA[Dec ramp adapt.] parameter, IF APPLICATION ALLOWS. Not possible if the [BRAKE LOGIC CONTROL] function is active; 
- Use a braking resistor 
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