Brake resistor short circuit

What does 25 mean?

The brake resistor is monitored during operation. If a short circuit occurs, the brake function is disabled and the warning appears. The frequency converter is still operational, but without the brake function.

• Physical damage to the brake resistor causing an internal short circuit (e.g., melted coil, carbon tracking).
• Short circuit in the wiring connecting the brake resistor to the drive (e.g., between terminals 81 and 82).
• Moisture ingress or conductive contamination causing a short circuit across the resistor terminals or winding.
• Faulty brake chopper IGBT failing in a continuously conductive (shorted) state, simulating a resistor short.
• Incorrectly rated brake resistor installed, leading to premature failure and shorting under load.

Click steps to track your progress.

1. 1

   Safely de-energize the drive. Disconnect the brake resistor wiring from the drive terminals (e.g., 81, 82).

2. 2

   Measure the resistance across the brake resistor terminals (e.g., 81 and 82) with an ohmmeter; it should match the specified value.

3. 3

   Measure the insulation resistance between each brake resistor terminal (e.g., 81, 82) and ground; it should be infinite.

4. 4

   Visually inspect the brake resistor and its wiring for signs of physical damage, arcing, or burnt insulation.

5. 5

   Test the brake chopper circuit's IGBT for short circuits using a multimeter in diode test mode across its terminals.