BC short circuit

What does 7191 mean?

A short circuit has been detected within the brake chopper circuit, specifically occurring when an earth fault condition is also present and the brake chopper is active. This is a severe fault that can lead to rapid destruction of the brake chopper power components and poses a safety risk due to high current flow.

• Short circuit between brake chopper transistor and heatsink (earth) due to insulation failure or component damage.
• Short circuit in the brake resistor wiring or the brake resistor itself (e.g., internal breakdown, resistance too low).
• Damage to the brake chopper module (IGBT, diode, control circuit) causing a direct short.
• Conductive contamination or foreign objects bridging terminals within the brake chopper or brake resistor enclosure.
• Simultaneous earth fault condition combined with active braking, exposing a latent chopper circuit weakness.

Click steps to track your progress.

1. 1

   De-energize the drive. Disconnect the brake resistor connections (e.g., terminals R+, R- or B+, B-).

2. 2

   Measure resistance across the brake resistor terminals; verify it matches the specified resistance (e.g., 20 ohms, 50 ohms).

3. 3

   Measure insulation resistance from each brake resistor terminal to ground (PE) using a megohmmeter (500V).

4. 4

   Measure continuity between the drive's internal brake chopper terminals (e.g., DC+ to BRK, DC- to BRK) to check for internal shorts (expect open circuit when not switching).

5. 5

   Inspect the brake chopper module for visible damage, scorch marks, or loose connections.