Brake resistor short-circuited

What does 25 mean?

The external brake resistor connected to the drive has developed a short circuit, disabling the brake function. This prevents the drive from dissipating regenerative energy, potentially leading to a DC overvoltage trip during deceleration.

• Internal insulation breakdown within the braking resistor itself, leading to a phase-to-phase or phase-to-ground short.
• Damage to the wiring connecting the braking resistor to the drive's B1/B2 terminals, causing conductors to short together or to ground.
• Moisture, conductive dust, or foreign metallic objects (e.g., loose screws) creating a short circuit across the resistor terminals or within its housing.
• Overheating of the brake resistor leading to physical deformation and internal shorts (e.g., due to excessive braking cycles or undersizing).
• Faulty detection circuit within the drive incorrectly sensing a short circuit on the B1/B2 terminals.

Click steps to track your progress.

1. 1

   Disconnect the external braking resistor from the drive's B1 and B2 terminals.

2. 2

   Measure the resistance of the braking resistor using an ohmmeter, comparing it to the nominal resistance value specified on its nameplate (e.g., 20 Ohms).

3. 3

   Perform an insulation resistance test (Megger test) on the braking resistor element to its casing/ground, expecting >1 Megaohm.

4. 4

   Visually inspect the braking resistor and its wiring for any signs of physical damage, overheating, arcing, or foreign objects.

5. 5

   If the fault clears after disconnecting the resistor, test the drive with a known good, correctly sized braking resistor to confirm the fault source.