KUKA KSS01306 DC Bus Overvoltage Error – Causes, Symptoms & How to Fix

• Error Code: KSS01306
• Category: Power Supply / Drive System
• Severity: High
• System: KRC4 / KSP Drives
• Impact: axis disabled, robot stops, potential drive protection triggered

Quick Fix for KUKA KSS01306

If th is error appears during operation:

• Stop the robot and reset the controller
• Check if the error occurs during deceleration or braking
• Reduce speed and acceleration (especially deceleration ramps)
• Inspect braking resistor connections
• Restart and test at low speed

⚠️ Always power off before checking cabinet components.

If the error only happens when the robot slows down or stops, the issue is almost always regenerative energy not being absorbed properly.

What Is KUKA KSS01306?

KSS01306 is triggered when the DC bus voltage rises above the maximum threshold.

Th is usually happens when:

• The robot decelerates
• Motors act as generators
• Energy flows back into the DC bus

Normally, th is energy is absorbed by the braking resistor. If not, voltage spikes → system trips → robot stops.

Typical Symptomson Site

• Robot stops suddenly during deceleration
• Error appears at the end of motion cycles
• KSP drive shows red LED
• Robot runs fine at low speed but fails at high speed
• Motion feels unstable before stopping

👉 Classic pattern:
“Runs fine → slows down → trips with KSS01306”

Common Causes (Field Experience)

1. Braking Resistor Failure (Most Common)

• Resistor disconnected or burned out
• Wiring issue between resistor and cabinet
• Incorrect resistor specification

👉 Without it, regenerative energy has nowhere to go

2. High-Speed Deceleration / Heavy Load

• Large payload
• Aggressive deceleration settings
• Multiple axes braking simultaneously

👉 Generates excessive energy → voltage spike

3. Power Supply Instability

• Incoming voltage too high
• Sudden voltage fluctuations
• Grounding issues

4. KSP Drive Regulation Fault

• Drive fails to manage bus voltage
• Internal protection triggered
• Aging electronics

5. DC Bus Component Issues

• Capacitors not absorbing energy properly
• Internal bus imbalance

6. Parameter or Firmware Problems

• Incorrect DC bus limits
• Mismatch between KRC4 and KSP firmware
• Corrupted parameters

Step-by-Step Troubleshooting

Step 1 – Identify When the Error Occurs

• During braking? → check resistor
• During startup? → check power
• Random? → check drives or cables

Step 2 – Check Braking Resistor (Critical)

• Inspect wiring and connectors
• Measure resistance value
• Check for overheating or damage

👉 Th is step alone solves a large percentage of cases

Step 3 – Monitor DC Bus Voltage

SmartHMI → Drive Diagnostics → DC Bus

• Watch voltage during motion
• Look for spikes during deceleration

Step 4 – Inspect Drives

• Check KSP LED status
• Swap modules if needed
• Look for overheating signs

Step 5 – Reduce Motion Load

• Lower speed and acceleration
• Smooth deceleration curves
• Reduce payload if possible

Step 6 – Verify Power Supply

• Measure incoming voltage
• Check grounding
• Inspect main contactor

Step 7 – Replace Faulty Components

If needed:

• Braking resistor
• KSP drive
• DC bus components
• Power modules

Recommended Replacement Parts

• KUKA KSP 600-3x20 (00-198-265) Servo Drive: For internal overvoltage or electronics faults.
• Braking Resistors (KUKA OEM spec): To absorb regenerative energy during deceleration.
• Motor Power Cables and Connectors (High-flex, Shielded): Ensure reliable voltage delivery.
• Power Supply Monitoring Modules: For early detection of DC bus voltage excursions.

⚠️ Compatibility Tip: Confirm KSP module type, axis number, and KSS version before replacing drives or power components.

Pro Diagnostic Tip for KUKA KSS01306

• Navigate to SmartHMI → Drive Diagnostics → DC Bus Monitoring.
• Monitor DC bus voltage and current in real-time.
• Log overvoltage events to identify patterns during high-load or braking.
• Verify regenerative energy absorption by braking resistors.
• Persistent KSS01306 indicates potential aging or failure in drive electronics.

How to Fix KSS01306

• Repair or replace braking resistor
• Reduce aggressive deceleration
• Stabilize power input
• Replace faulty KSP drive
• Check DC bus components

Prevention & Maintenance

• Regularly inspect cabinet power supply, DC bus, and drives.
• Maintain stable incoming voltage and grounding.
• Ensure braking resistors are functioning properly.
• Avoid overloading axes or sudden deceleration.
• Replace aging drives and components proactively.

Related KUKA Errors

⚠️ Technical Note: DC bus overvoltage often triggers or correlates with:

• KSS01305DC Bus Undervoltage Error – Voltage fluctuations in the same DC bus.
• KSS00401Motor Error– Drive/motor current interruptions caused by bus issues.
• KSS01404Servo Drive Error– KSP drive internal faults linked to bus overvoltage.
• KSS00406Position Deviation Error– Overvoltage causing torque spikes and axis deviation.

FAQ About KUKA KSS01306

What does KSS01306 mean?

DC bus voltage is too high, and the system stopped to protect hardware.

Can the robot keep running?

No. Motion is blocked until voltage returns to safe levels.

What is the most common cause?

👉 Braking resistor failure or disconnection

Can speed or braking cause th is?

Yes. Fast deceleration generates regenerative energy that can trigger overvoltage.

Fastest way to fix it?

1. Check braking resistor
2. Reduce speed/deceleration
3. Monitor DC bus
4. Replace faulty components