Siemens F30003 alarm: SINAMICS: DC link undervoltage

The SINAMICS drive detects insufficient voltage on the DC link during operation or startup. It is an alarm from the Power supply area, and in the catalog it is listed as “SINAMICS: DC link undervoltage”. On the machine you notice it like this: The drive disables, Axis/spindle drops out when accelerating, May appear with mains dips.

On the shop floor it almost always comes from one of these causes: Low feeding, Line module, Fusible/contactor, Network drop under load. Rule out the most likely one on your machine first, before touching parameters or swapping anything.

Reset after restoring stable power. Resetting without fixing the cause first only hides the problem: Siemens F30003 trips again and, in the meantime, you keep working with the machine in bad shape.

With the machine stopped and in a safe state, start with these checks: Note F30003 and r0949, Have qualified personnel check the mains, Revisar LEDs line module. That alone will tell you whether it is the program or whether you need to raise a maintenance job.

With Siemens F30003 active, avoid this: Do not bypass safety devices, Do not manipulate energized electrical cabinet, Do not continue producing if the alarm reappears. Skipping any of these points is what turns a minor stop into an expensive breakdown.

Always, if it repeats. If you are not sure how far it goes, stop the machine and report it: a repeat alarm always works out cheaper than a crash.

It is critical: there is a real risk of damage to the machine, the tool or a person. Leave the machine stopped, do not keep resetting it to see if it goes away, and call maintenance before producing again. Guidance reference. Always confirm the full text in the exact machine/control manual.