Fagor alarm 4010: Overvoltage at the power bus (drive errors 304/306; 4011 = undervoltage, error 307)
CNC 8055 SERCOS drive error (DDS) · Fagor DDS drives
What it means
DC-bus voltage rose above the hardware/software threshold - braking energy cannot be absorbed, or line supply is abnormal.
Likely causes
- external/internal ballast (braking) resistor open-circuit or burnt
- power supply module ballast/crowbar circuit failed
- mains spikes or heavily unbalanced/regenerative line (4011: mains <380 V, loose bus bars, blown PS fuse)
Triage note: Ohm-out the ballast resistor cold - an open ER resistor is the classic cause on vertical axes with fast decel. Undervoltage twin (4011/E307) points instead to line side: torque bus-bar screws and measure under load.
Replacement parts
We supply the following units for this alarm — tested, warranty-backed:
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ER+TH
External ballast resistor with thermostat · Primary suspect
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PS-25B4 / XPS-25 (rating-match)
Power supply module (crowbar/ballast stage) · Common cause
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CM 1.60
Capacitor module (weakened bus buffering) · Check if others ruled out
Need the part urgently?
Send us alarm 4010 with your machine details — typical RFQ turnaround is 24–48h.