Siemens G120 displaying Fault F30002? Learn how to troubleshoot DC link overvoltage, adjust ramp-down times, and configure voltage controllers to prevent VFD trips.
If your Siemens SINAMICS G120 drive trips and displays Fault F30002, it means the internal DC link voltage has exceeded the safe operating threshold. Think of the DC link as the “energy reservoir” of the drive. When this reservoir overflows with too much electrical energy, the drive shuts down instantly to protect its internal power modules (IGBTs) from exploding.
While this fault is common during braking or deceleration, it can also be caused by power supply instability. Here is a human-made guide to understanding the causes and applying the correct remedies.
What Triggers Fault F30002?
The G120 monitors the voltage on the DC bus constantly. The trip typically happens for one of four reasons:
- Motor Regeneration: When you command a motor to slow down, it acts as a generator. This energy is “pumped” back into the drive. If the drive cannot dissipate this energy (via a braking resistor) or control it, the voltage spikes.
- High Line Supply Voltage: The incoming AC power from your facility is higher than the drive’s rated limit.
- Line Phase Interruption: If one of the three input phases drops out or becomes unbalanced, it can cause the DC link to fluctuate and spike.
- Controller Settings: The internal software feature meant to manage these voltage rises is either turned off or poorly tuned.
Step-by-Step Troubleshooting & Remedies
1. Adjust the Deceleration Ramp (p1121)
The most frequent cause of F30002 is trying to stop a heavy load too quickly. If you don’t have an external braking resistor, the drive has nowhere to put that regenerative energy.
- Action: Increase the Ramp-down time (p1121). By slowing down the motor more gradually, you reduce the rate at which energy is fed back into the DC link.
2. Use Smoothing/Rounding Times (p1130, p1136)
Abrupt changes at the start or end of a speed ramp can cause voltage “sloshing” in the DC link.
- Action: Set the Rounding times (p1130 and p1136). This adds an “S-curve” to the ramp, making the transition from running to stopping much smoother and preventing sharp voltage peaks.
3. Activate the Vdc Controller (p1240 or p1280)
Siemens G120 drives have a built-in feature called the Vdc_max controller. When active, if the drive sees the voltage rising too high, it will automatically extend the deceleration time to keep the voltage under the trip point.
- Action: Set p1240 (for Vector Control) or p1280 (for U/f Control) to 1 (Enable Vdc_max controller).
- Note: If this is already enabled and you still get trips, you may need to “adapt the dynamic response” by adjusting the controller gains.
4. Verify Line Supply and p0210
Sometimes the problem is coming from the power grid itself.
- Action: Use a multimeter to measure your incoming L1, L2, and L3 phases. Ensure they are balanced.
- Action: Check parameter p0210 (Drive unit line supply voltage). Ensure this matches your actual measured facility voltage. If p0210 is set to 400V but your supply is actually 480V, the drive will trip much earlier than it should.
Summary Checklist
| Parameter | Description | Remedy Action |
|---|---|---|
| p1121 | Ramp-down time | Increase the value (seconds). |
| p1240 / p1280 | Vdc_max controller | Set to 1 (Enable). |
| p0210 | Line supply voltage | Ensure it matches physical measurement. |
| p1130 / p1136 | Rounding times | Increase for a smoother S-curve ramp. |
When do you need a Braking Resistor?
If your application requires you to stop a high-inertia load (like a large fan or a heavy centrifuge) very quickly, no amount of parameter tuning will clear F30002. In this case, the physics demand a Braking Resistor. This hardware allows the drive to safely “burn off” the excess energy as heat.
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