What the 1011 alarm means

DC bus voltage fell below the lower limit; the drive cannot hold axis torque and trips out. We are very familiar with this alarm on EFORT EC2-S controller + TSINO drives systems — usually the first on-site inspection is enough to confirm the cause.

Most common causes

  • Supply voltage low or momentary dip
  • Blown input fuse or missing phase
  • Loose main terminals
  • Inrush resistor damaged by frequent power cycling
Field note: Our ticket data shows the first cause is by far the most common — start there to avoid dead ends.

Step-by-step field fix

  1. Measure supply voltage under load
  2. Check all three phases and fuses
  3. Tighten main terminals and inspect for heat discoloration
  4. Reduce ON/OFF cycling frequency
  5. If the supply is clean, replace the drive
Safety first: For EFORT 1011, this alarm family involves the DC bus, which sits at several hundred volts and stays charged for minutes after power-off - touching terminals is a shock hazard. On site you may not carry out the first step yourself: Measure supply voltage under load. Beyond that it is the DC bus and power stage work - leave it to a professional. On EFORT 1011: checking incoming voltage at the disconnect and looking at breakers and fuses is fine to do yourself; opening the cabinet to touch bus terminals or pulling power modules needs a qualified electrician.

How we diagnose drive alarms on site

EFORT 1011 belongs to the drive & power stage family. On EFORT 1011 the failing stage is matched servo drives assigned per axis in the cabinet on the EFORT robot controller - the fault sits on the energy chain: mains input, rectification, DC bus, braking resistor, inverter power devices and the drive board. We start reading EFORT 1011 at the pendant alarm list (four-digit codes, 1xxx / 3xxx / 4xxx segments).

The chain involved in EFORT 1011 runs: three-phase mains -> rectifier -> DC bus (bus capacitors) -> brake chopper / braking resistor -> inverter (IGBT) -> motor.

Supply voltage low or momentary dip is common on EFORT 1011, but look at the duty cycle: Cells with high-inertia loads or frequent start-stop cycles return far more regenerative energy than a plain transfer cell, and the braking resistor lives in a hot cycle that shortens its life. When we suspect this family we ask what changed: if the takt was raised recently or a heavier fixture went on, the alarm cluster usually lines up with that process change. Replacing the resistor alone will not fix it - the chopper rating and resistor wattage have to be re-checked against the new duty.

Field notes on this page cover EFORT 1011 (Drive DC Bus Undervoltage (TSINO)); written by the Henghuan repair team, updated 2026-10-01.

Blocked by this alarm? We can help you analyze it over the phone

Give us the alarm code, the robot model and what it was doing when the alarm hit. Our engineers run these diagnostics daily, and remote diagnosis by phone or video is free.

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Related Drive & Power Stage alarms

1001 — Drive Overcurrent (TSINO Servo) 1010 — Drive DC Bus Overvoltage (TSINO) 1020 — Motor Overload (TSINO)
Same family: this code belongs to the Drive & power stage alarms family - the page collects all Drive & power stage-family codes we have handled, with the common inspection order and spares.
Other brands: we also keep field-fix libraries for JAKA · AUBO · ROKAE and more — see the complete alarm code hub.

Frequently asked questions

QWhat does the EFORT 1011 alarm mean?

DC bus voltage fell below the lower limit; the drive cannot hold axis torque and trips out. We are very familiar with this alarm on EFORT EC2-S controller + TSINO drives systems — usually the first on-site inspection is enough to confirm the cause. EFORT 1011 sits in the drive & power stage family; on our work orders the highest-frequency trigger for this code is "Supply voltage low or momentary dip".

QCan I clear a EFORT 1011 alarm myself?

Whether EFORT 1011 clears on its own depends on the outcome of "Measure supply voltage under load". Finish the flow with "If the supply is clean, replace the drive" to confirm EFORT 1011 - do not skip it. If that step is clean, the second most frequent cause on EFORT 1011 is "Blown input fuse or missing phase". If EFORT 1011 returns after two clears, or the checks point at Supply voltage low or momentary dip, stop the cell and call a professional robot repair engineer.

QFor drive/power alarms like EFORT 1011, what spares do you bring on site?

The commonest causes we see on EFORT 1011 are "Supply voltage low or momentary dip, Blown input fuse or missing phase, Loose main terminals", so we stock the van against those. For EFORT 1011 specifically, we stock the van along the energy chain: braking resistors, bus capacitors, input fuses, drive-board supply parts and the common power modules for the brand. For EFORT 1011, drive alarms usually stop the whole line, so they sit at the front of our dispatch queue. Before we roll, tell us what EFORT 1011 shows on the pendant alarm list (four-digit codes, 1xxx / 3xxx / 4xxx segments) and what the machine was doing - phone or video triage is free.

This page on EFORT 1011 is based on the field experience of the Henghuan Robotics repair team. Alarm explanations are our own summary for troubleshooting reference and may differ across controller and software versions — if unsure, verify against EFORT documentation or reach out to us. Henghuan is an independent service provider with no affiliation or endorsement by EFORT.