Internal Braking Transistor Fault

What does Braking Transistor Fault mean?

The internal braking transistor within the drive, which is responsible for dissipating regenerative energy from the motor, has malfunctioned or failed. This is a hardware fault within the drive that can prevent proper braking, lead to DC overvoltage faults, or cause unstable operation.

• Failure of the internal IGBT (Insulated Gate Bipolar Transistor) that forms the braking chopper, due to thermal stress or overcurrent.
• Short circuit or open circuit in the external braking resistor or its connecting wires to terminals (e.g., B1, B2).
• Repeated high-energy braking cycles exceeding the drive's continuous braking capacity, causing component degradation.
• Faulty gate drive circuit for the braking transistor on the control board, preventing proper switching.
• DC bus overvoltage condition that repeatedly attempts to activate the braking chopper, eventually causing failure.

Click steps to track your progress.

1. 1

   1. Power down the drive completely (wait for DC bus discharge). Disconnect the external braking resistor from terminals (e.g., B1, B2). If the fault clears on power-up, the resistor or its wiring is suspect.

2. 2

   2. Measure the resistance of the external braking resistor with an ohmmeter to ensure it matches the specified value and is not open or shorted.

3. 3

   3. Visually inspect the drive's internal components (if safe and accessible for qualified personnel) for signs of damage on the braking transistor module (e.g., burn marks, cracked casing).

4. 4

   4. Verify the drive's DC bus voltage (U1-03) is within normal operating range and not experiencing sustained overvoltage conditions that would stress the braking chopper.

5. 5

   5. If the fault persists after external resistor checks, the internal braking transistor is likely damaged and requires drive repair or replacement by a qualified service technician.