DB Resistor Overheat

What does RH mean?

The RH fault signifies that the dynamic braking (DB) resistor has overheated, detected when its duty cycle exceeds 3% as monitored by the inverter's software. This protection mechanism prevents damage to the resistor from excessive braking energy, causing the inverter to coast to a stop.

• Excessive or prolonged regeneration from the motor, requiring the DB resistor to dissipate too much energy (e.g., fast deceleration of high inertia loads).
• Braking resistor sized incorrectly (resistance too high, power rating too low) for the application's braking energy requirements.
• Faulty or degraded braking resistor element (internal open circuit or short) causing localized overheating or miscalculation by the inverter.
• Braking transistor (IGBT) within the inverter failing to switch properly, causing continuous current flow through the resistor.
• Incorrect setting of braking parameters (e.g., deceleration time set too short in P1-09, or DB resistor duty cycle limits in L3-01/L3-02) for the application.

Click steps to track your progress.

1. 1

   1. Measure the resistance of the external braking resistor (terminals P+ and B1/B2) with an ohmmeter and compare to the specified value (e.g., 20 Ohms ±5%).

2. 2

   2. Monitor the motor's deceleration time (Parameter P1-09) and the frequency of braking events during operation to assess regeneration energy.

3. 3

   3. Inspect the braking resistor for physical damage, discoloration, or signs of overheating (e.g., charred insulation).

4. 4

   4. Verify the inverter's braking parameters (e.g., L3-01 for DB resistor resistance, L3-02 for DB resistor capacity, P1-09 for deceleration time) are correctly set for the connected resistor and application.

5. 5

   5. If the application requires frequent or rapid braking, consider installing a larger power-rated braking resistor or an external braking unit with active energy management.

6. 6

   6. Check for proper cooling and airflow around the braking resistor; ensure it's not enclosed in a restricted space.