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KUKA Robot Controller
Power Supply · Intermediate
KUKA Robot KRC0123 - Undervoltage
The DC bus voltage in the KPP has dropped below the minimum operating threshold, typically below 280VDC for 400VAC systems or 140VDC for 230VAC systems. This condition indicates insufficient power supply to the servo drives and triggers an immediate controlled stop. The robot cannot execute motion commands until proper voltage levels are restored and the fault condition is cleared.
KRC0123
KUKA Robot KRC0123 - Undervoltage
Undervoltage
The DC bus voltage in the KPP has dropped below the minimum operating threshold, typically below 280VDC for 400VAC systems or 140VDC for 230VAC systems. This condition indicates insufficient power supply to the servo drives and triggers an immediate controlled stop. The robot cannot execute motion commands until proper voltage levels are restored and the fault condition is cleared.
Common Causes
- Incoming mains supply voltage drop or instability from facility power distribution, often caused by heavy machinery startup, welding equipment, or inadequate transformer capacity on the same circuit
- Degraded or failing DC link capacitors in the KPP power supply section reducing the ability to maintain stable bus voltage under load conditions
- Loose or corroded connections at main power input terminals X101 on KPP, or at motor power output connectors causing voltage drop under current demand
- Undersized facility wiring or excessive voltage drop in long cable runs from main distribution panel to robot controller exceeding 3-5 percent loss
- Simultaneous high-current demand from multiple axes during rapid coordinated moves exceeding the power supply capacity or triggering brownout conditions
Troubleshooting Steps
- 1Step 1: Check incoming AC line voltage at KRC4 main power input X101 using a multimeter, verify it is within +/- 10 percent of nominal (400VAC systems: 360-440VAC, 230VAC systems: 207-253VAC)
- 2Step 2: Inspect all power connection terminals at KPP input and motor output stages for tightness, discoloration, or signs of arcing, torque to specification per installation manual
- 3Step 3: Monitor DC bus voltage in real-time through Service display or WorkVisual online diagnostics during program execution to identify voltage sag patterns correlating with specific motion segments
- 4Step 4: Review facility electrical supply quality with plant maintenance, consider installation of power line monitor to capture transient voltage events or request utility company power quality audit
- 5Step 5: Reduce peak power demand by optimizing motion profiles with lower acceleration values, implementing velocity blending, or adding brief delays between high-load motion segments
- 6Step 6: If voltage remains unstable with confirmed good input power, measure DC bus ripple voltage and capacitor ESR values, replace KPP capacitor bank or entire power supply module if out of specification, escalate to KUKA service for power electronics evaluation
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