Siemens alarm F30055: Power unit: Braking chopper overcurrent

What it means

The braking chopper - the ballast circuit that dissipates regenerative energy in a resistor when no regenerating infeed is present - detected an overcurrent. This almost always means the braking resistor or its wiring is shorted or overloaded. The chopper stays disabled until the fault is acknowledged AND a new pulse enable is issued.

Likely causes

• braking resistor short-circuit or internal failure
• external braking resistor dimensioned too small (ohms/power)
• chopper output stage defective

Replacement parts

We supply the following units for this alarm — tested, warranty-backed:

• 6SN1113-… / 6SE7000-… braking resistor (match kW)

  infeed · Common cause

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