What the A.30 alarm means

Energy fed back from the motor during deceleration exceeded what the regenerative circuit and braking resistor can absorb; the DC bus voltage rises and the drive trips. This is one of the faults our repair team handles on ESTUN ERC / ED3L controller + ESTUN servo systems — the cause is usually identifiable within the first on-site inspection.

Most common causes

  • Deceleration too fast for the payload and inertia
  • Braking resistor undersized, open-circuit, or degraded
  • Regenerative parameter set lower than the installed resistor capacity
  • Vertical axis dropping load without enough braking capacity
Field note: the first item on this list is what we find most often on real machines. Check it before you go deeper.

Step-by-step field fix

  1. Measure the braking resistor resistance against specification
  2. Check the resistor wiring for an open circuit — a broken resistor wire turns every decel into an alarm
  3. Soften the deceleration ramps in the failing move
  4. Set the regenerative capacity parameter to match the actual resistor
  5. Upgrade to a larger external resistor if the duty cycle is inherently high
Safety first: never bypass safety circuits or force contactors closed. If the alarm involves E-stop chains, brakes or drive power, and you are not a trained robot technician, contact a professional — wrong moves here can cost you a robot or an injury.

Still stuck? Get an engineer on the phone — right now

Tell us the alarm code, the robot model and what was happening when the alarm came up. Our engineers run these diagnostics every day, and remote diagnosis by phone or video call is free.

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

Related Drive & Power Stage alarms

A.02 — Parameter Setting Error A.10 — Overcurrent A.40 — Main Circuit Overvoltage A.41 — Main Circuit Undervoltage A.71 — Overload — Instantaneous High Load A.72 — Overload — Continuous Over-torque
Other brands: we also keep field-fix libraries for INOVANCE · EFORT · JAKA and more — see the complete alarm code hub.

Frequently asked questions

QWhat does the ESTUN A.30 alarm mean?

Energy fed back from the motor during deceleration exceeded what the regenerative circuit and braking resistor can absorb; the DC bus voltage rises and the drive trips. In field practice it belongs to the drive & power stage family of faults.

QCan I clear a ESTUN A.30 alarm myself?

Sometimes. Work through the step-by-step checks on this page — the first listed cause is what we find most often in the field. If the alarm returns after two attempts, or the fault involves power, brakes or safety circuits, stop and call a qualified robot service engineer.

QHow fast can a Henghuan engineer help?

On-site response in the Pearl River Delta within 30 minutes to 3 hours, across mainland China in 1-3 business days, and worldwide within 2-5 business days. Remote diagnosis by phone/WhatsApp/video is available immediately.

Written by the Henghuan Robotics repair team from field service experience. Alarm descriptions are our own summary for troubleshooting reference and may vary by controller and software version — when in doubt, check your ESTUN documentation or contact us. Henghuan is an independent service provider, not affiliated with or endorsed by ESTUN.