Brake resistor wiring

What does A792 mean?

A short circuit has been detected in the brake resistor or a fault within the brake chopper itself. This condition prevents the safe dissipation of regenerative energy and can lead to damage to the brake chopper components, potentially causing further drive faults.

• Short circuit across the brake resistor terminals or within the brake resistor wiring, leading to excessive current flow when the chopper attempts to activate.
• Internal short circuit within the brake resistor element itself, often due to physical damage or catastrophic failure.
• Failed brake chopper IGBT (Insulated Gate Bipolar Transistor) that is permanently shorted, causing continuous conduction and high current draw from the DC bus.
• Incorrect brake resistor resistance value (e.g., too low) specified in P43.01, causing the drive to detect an apparent short circuit due to unexpectedly high current.
• Moisture ingress or conductive debris within the brake resistor enclosure or terminals, creating a path for a short circuit.

Click steps to track your progress.

1. 1

   1. Power down and lock out the drive. Disconnect the brake resistor wiring from the drive's terminals (e.g., R+, R-).

2. 2

   2. Use an ohmmeter to measure the resistance of the brake resistor. A reading significantly lower than the value in P43.01 or near zero ohms indicates a short circuit.

3. 3

   3. Inspect the brake resistor wiring for any signs of insulation damage, pinched wires, or conductors touching, particularly where wires enter conduit or terminal blocks.

4. 4

   4. Visually examine the brake resistor for any external damage, burn marks, or signs of arcing that could indicate an internal short.

5. 5

   5. If the resistor checks out as OK, and the fault persists, it strongly suggests an internal fault with the drive's brake chopper. In this case, consult drive diagnostics (e.g., DC bus voltage P06.01) to confirm the chopper is drawing excessive current.