Dynamic Braking Resistor Overload

What does RH mean?

The protection for the dynamic braking resistor, based on setting of L8-01, has been activated. This fault is typically caused by an overhauling load, an extended dynamic braking duty cycle that exceeds the resistor's capacity, or a defective dynamic braking resistor, leading to overheating.

• Dynamic braking resistor (DBR) ohmic value (L8-02) or capacity (L8-01) parameters are incorrectly set, not matching the installed resistor's specifications.
• Excessive regenerative energy generated by an overhauling load (e.g., crane, high inertia flywheel), causing the DBR to dissipate power for too long or too frequently.
• The dynamic braking duty cycle (e.g., deceleration time C1-02, brake duty cycle L8-03) is too high for the installed DBR's continuous power rating.
• Poor cooling or inadequate ventilation for the dynamic braking resistor, leading to overheating even within its rated duty cycle.
• Faulty dynamic braking transistor (chopper circuit) on the drive or external braking unit, causing continuous current flow through the DBR.
• Loose or high resistance connections in the DBR wiring (terminals +2, B1, B2), leading to localized overheating or incorrect resistance sensing.

Click steps to track your progress.

1. 1

   1. Verify the dynamic braking resistor parameters L8-01 (DBR capacity in kW) and L8-02 (DBR resistance in Ohms) against the actual installed resistor's nameplate data.

2. 2

   2. Disconnect the DBR and measure its ohmic value between the drive's B1 and B2 terminals (or +2 and B1 for external units) with a multimeter to confirm it matches L8-02.

3. 3

   3. Increase the motor's deceleration time parameter (C1-02) to reduce the rate of energy regeneration, thus spreading the load on the DBR over a longer period.

4. 4

   4. Review the application for continuous overhauling loads. If present, consider alternative solutions like common DC bus or active front end drives.

5. 5

   5. Inspect the dynamic braking resistor for proper ventilation and ensure its cooling fan (if present) is operational and not obstructed.

6. 6

   6. Reduce the dynamic braking duty cycle parameter (e.g., L8-03) or install a higher capacity (kW) dynamic braking resistor with appropriate resistance.