Braking Transistor Overload Fault

What does boL mean?

The internal braking transistor is experiencing an overload, typically due to a high regeneration power or an excessive repetition frequency during braking cycles. This can also trigger if the transistor's protective function is enabled incorrectly while a regenerative converter is present, or if the transistor itself is faulty. Prolonged overload can lead to component damage and potential drive failure.

Additional Steps

Steps 1–2 are listed in Priority Fix.

1. 3

   If a regenerative converter is installed, set parameter L8-55 (Internal DB Transistor Protection Selection) to '0' (Disable).

2. 4

   If the fault persists after performing the above steps, the internal braking transistor may be damaged, requiring replacement of the drive unit.