The error "Intermediate circuit voltage out of permitted range" on a KUKA robot indicates that the voltage in the DC bus (intermediate circuit) of the robot controller is outside the acceptable range. This intermediate circuit voltage is crucial for the proper functioning of the servo drives and other components that rely on stable power.

Common Causes:

1. Power Supply Issues:

   • Fluctuations or instability in the main power supply can cause the intermediate circuit voltage to deviate from the permitted range.

2. Regenerative Energy:

   • During braking or deceleration, the robot’s motors can generate regenerative energy that feeds back into the intermediate circuit. If not properly managed, this can cause the voltage to spike.

3. Faulty Components:

   • A malfunctioning power supply unit (PSU), DC bus capacitors, or other components within the power electronics can lead to incorrect intermediate circuit voltage.

4. Overload Conditions:

   • If the robot is operating under conditions that cause excessive current draw, this can lead to voltage instability in the intermediate circuit.

5. Temperature Issues:

   • High temperatures within the controller can affect the performance of power electronics, leading to voltage deviations.

6. Grounding or Short Circuit:

   • Poor grounding or a short circuit in the controller can cause voltage irregularities in the intermediate circuit.

7. Inadequate Circuit Protection:

   • Faulty or inadequate protection devices, such as fuses or circuit breakers, might fail to regulate the voltage effectively.

Steps to Troubleshoot and Resolve:

1. Check the Power Supply:

   • Verify that the mains power supply to the robot is stable and within the specified voltage range.
   • Ensure that the power supply unit (PSU) is functioning correctly and delivering the appropriate voltage to the intermediate circuit.

2. Monitor Regenerative Energy:

   • During robot operation, monitor the system for instances where regenerative energy could be causing voltage spikes. This can happen during rapid deceleration or braking.
   • If necessary, adjust the braking resistor or other energy management settings in the controller to handle regenerative energy more effectively.

3. Inspect the Intermediate Circuit Components:

   • Open the controller and visually inspect the DC bus capacitors and other related components for signs of wear, damage, or leakage.
   • Test the capacitors if possible, or consider replacing them if they are old or show signs of degradation.

4. Check for Overloads:

   • Review the robot’s operation and any recent changes to the program or load that might cause excessive current draw.
   • Reduce the load or adjust the operating conditions to prevent overload conditions.

5. Inspect for Temperature Issues:

   • Ensure that the controller is adequately cooled and that all fans and vents are working correctly.
   • Check the ambient temperature around the controller and make sure it is within the acceptable operating range.

6. Verify Grounding and Wiring:

   • Check the grounding of the robot and controller to ensure it is properly connected and free of corrosion or damage.
   • Inspect the wiring for any signs of short circuits or loose connections that could affect the intermediate circuit voltage.