Brake chopper fault

What does 27 mean?

This warning/alarm indicates a short circuit in the brake IGBT, which disables the brake function. A critical consequence is that substantial power is continuously transmitted to the brake resistor, even if the brake function is inactive, creating a high voltage hazard and risking severe overheating of the resistor. This fault can also be triggered by an overheated brake resistor (using Klixon inputs 104 and 106) or in 12-pulse frequency converters if a disconnect or circuit breaker is opened while the unit is operating.

Additional Steps

Steps 1–2 are listed in Priority Fix.

1. 3

   Inspect the brake IGBT for visual signs of damage or short-circuiting; a qualified technician should diagnose and replace the power card or entire drive if the IGBT is faulty.

2. 4

   Check the brake resistor's thermal protection (Klixon inputs 104 and 106) for proper functionality and signs of previous overheating.

3. 5

   For 12-pulse systems, ensure that main disconnects or circuit breakers are never opened while the frequency converter is powered on.