Mitsubishi Electric · FR E700
This brake transistor alarm detects an issue caused by large regenerative energy from the motor, tripping the inverter. This fault signals potential overheating or overstress of the brake transistor circuit. Immediate power-off is critical to prevent component damage.
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Measure the resistance of the external braking resistor (if installed) and compare it against the value set in Parameter Pr. 30.
Inspect the braking resistor for physical damage, signs of overheating, or disconnected wires.
Increase the deceleration time (Pr. 8) to reduce the rate of regenerative energy feedback to the inverter.
Verify that the braking resistor's power dissipation rating (watts) is sufficient for the application's duty cycle.
Confirm proper cooling airflow for both the inverter and any external braking resistor.
Measure the voltage across the braking resistor terminals during deceleration to confirm energy dissipation.