What the SRVO-047 alarm means

The control power supply voltage inside the amplifier dropped below the lower limit. We fix this FANUC R-30iA / R-30iB / R-30iB Plus fault almost daily, and one round of on-site checks usually confirms what is going on.

Most common causes

  • Incoming 3-phase voltage low or phase loss
  • Control power supply unit (CPS) degraded
  • Transformer tap mismatch
  • Poor connections on power input terminals
Field note: We have tallied real cases: the first cause tops the list, so start your diagnosis there.

Step-by-step field fix

  1. Measure incoming 3-phase voltage under load
  2. Check all phases present and terminals tight
  3. Verify transformer tap matches local supply
  4. If input is good, test/replace the control power supply
Safety first: For FANUC srvo-047, servo circuits are live and motor shafts and reducers rotate: measuring current waveforms or winding resistance means contact with live or moving parts. What you can check yourself first is Measure incoming 3-phase voltage under load; live servo circuits and rotating parts handling is not a DIY job.

How we diagnose servo alarms on site

FANUC srvo-047 belongs to the servo & drive family. On FANUC srvo-047 the failing stage is alpha-i / beta-i servo amplifiers with PSM supply modules and SVM servo modules (SPM where spindles fit) on the R-30iB Plus / R-30iB Mate Plus / R-30iA - the servo closed loop: current/velocity/position loop misbehaviour, motor-drive matching and load identification. We start reading FANUC srvo-047 at the iPendant ALARM screen (SRVO / MOTN / SYST / INTF prefixes) together with the amplifier's 7-segment status code.

The chain involved in FANUC srvo-047 runs: target -> position loop -> velocity loop -> current loop -> power output -> motor -> feedback -> loop compare.

The classic misjudgement on FANUC srvo-047 is here: The easiest misjudgement in this family is blaming the drive for mechanical drag. The discriminator is the current waveform: normal at no load but clearly raised and wavering under load points at mechanics (reducer, bearings, assembly stress); abnormal already at no load, or spiky and oscillating, points at electrics (drive, motor windings, feedback). We capture the waveform on site before concluding anything, and decide parts after measurement - which saves customers paying for swaps they did not need.

Field notes on this page cover FANUC srvo-047 (LVAL Alarm - Low Voltage); written by the Henghuan repair team, updated 2026-10-01.

Not sure? Don't force it — contact an engineer

Send the alarm code, the robot model and a description of what was happening at the alarm. Our engineers handle FANUC srvo-047 FANUC srvo-047 every day, and remote diagnosis by phone/video is free.

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Hotline: +86-20-39029800 · WhatsApp: +86-188-1886-2860

Related Servo & Drive alarms

SRVO-021 — SRDY Off (Group / Axis) SRVO-023 — Stop Error Excess (Group / Axis) SRVO-024 — Move Error Excess (Group / Axis) SRVO-043 — DCAL Alarm - Discharge Alarm SRVO-044 — HVAL Alarm - High Voltage SRVO-045 — HCAL Alarm - High Current
Same family: this code belongs to the Servo & drive alarms family - the page collects all Servo & drive-family codes we have handled, with the common inspection order and spares.
Other brands: see our KUKA, ABB, Yaskawa and Universal Robots field-fix libraries — or the full 10-brand hub.

Frequently asked questions

QWhat does the FANUC srvo-047 alarm mean?

The control power supply voltage inside the amplifier dropped below the lower limit. We fix this FANUC R-30iA / R-30iB / R-30iB Plus fault almost daily, and one round of on-site checks usually confirms what is going on. FANUC srvo-047 sits in the servo & drive family; on our work orders the highest-frequency trigger for this code is "Incoming 3-phase voltage low or phase loss".

QCan I clear a FANUC srvo-047 alarm myself?

Whether FANUC srvo-047 clears on its own depends on the outcome of "Measure incoming 3-phase voltage under load". Finish the flow with "If input is good, test/replace the control power supply" to confirm FANUC srvo-047 - do not skip it. If that step is clean, the second most frequent cause on FANUC srvo-047 is "Control power supply unit (CPS) degraded". When FANUC srvo-047 keeps coming back it is not a one-off trigger - especially if If input is good, test/replace the control power supply is where you get stuck. Do not keep producing through FANUC srvo-047.

QFor servo alarms like FANUC srvo-047, how do you tell motor from drive?

The commonest causes we see on FANUC srvo-047 are "Incoming 3-phase voltage low or phase loss, Control power supply unit (CPS) degraded, Transformer tap mismatch", so we stock the van against those. For FANUC srvo-047 specifically, we bring the scope and meter; motors and drives are stocked by type, and most cases are measured before parts are ordered. For FANUC srvo-047, on servo alarms we specifically avoid misjudgement: waveform first, parts second, so customers skip needless swaps. Before we roll, tell us what FANUC srvo-047 shows on the iPendant ALARM screen (SRVO / MOTN / SYST / INTF prefixes) together with the amplifier's 7-segment status code and what the machine was doing - phone or video triage is free.

The content on FANUC srvo-047 was written by Henghuan Robotics service engineers from hands-on repair experience. Alarm descriptions are our own reference summary and may differ by controller or software version — defer to FANUC documentation, or contact us to confirm. Henghuan is an independent service provider with no affiliation or endorsement by FANUC.