What the E0044 alarm means

The motor supply DC bus voltage is too high, usually from regenerative energy not being dissipated. This fault appears in a large share of our Nachi AW / FD series service tickets, and the first round of on-site checks usually finds the source.

Most common causes

  • Faulty or missing regenerative resistor
  • Aggressive deceleration with high inertia
  • Incoming supply too high
  • Regeneration circuit fault
Field note: Most of the time the problem is the first item on the list, so ruling it out saves you half the time.

Step-by-step field fix

  1. Check the regenerative resistor and circuit
  2. Reduce deceleration and load inertia
  3. Check incoming supply voltage
  4. Inspect the regeneration module
  5. Retest at lower speed
Safety first: For NACHI e0044, 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. What you can check yourself first is Check the regenerative resistor and circuit; the DC bus and power stage handling is not a DIY job. On NACHI e0044: 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

NACHI e0044 belongs to the drive & power stage family. On NACHI e0044 the failing stage is servo amplifier modules in the cabinet, assigned per axis on the AX-series / FD-series controllers - the fault sits on the energy chain: mains input, rectification, DC bus, braking resistor, inverter power devices and the drive board. We start reading NACHI e0044 at the pendant error-code screen (E-series codes) with amplifier panel indicators.

The chain involved in NACHI e0044 runs: three-phase mains -> rectifier -> DC bus (bus capacitors) -> brake chopper / braking resistor -> inverter (IGBT) -> motor.

When NACHI e0044 fires, the site usually reports Faulty or missing regenerative resistor first, but the real cause is often cooling: More than half of power-stage alarms are not a dead device but a device cooked by failed cooling. A stopped cabinet fan, a packed filter mat or a dusted air duct keeps IGBT junction temperature high: intermittent over-temperature first, hard fault days later. On these alarms we open the power module and look for cracked thermal paste and felted dust in the duct, then measure phase-to-phase output and insulation to frame. Swapping the module without cleaning the duct just buys the same failure again.

Field notes on this page cover NACHI e0044 (Motor Power Overvoltage); written by the Henghuan repair team, updated 2026-10-01.

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

Tell us these three: alarm code, robot model, and the operating condition at the alarm. NACHI e0044 NACHI e0044 is a diagnosis our engineers do daily, and phone/video remote diagnosis is free.

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Related Drive & Power Stage alarms

E0028 — Motor Power Voltage Drop E0032 — Overcurrent E0038 — Overload E0042 — Motor Temperature Rise Abnormal
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 Omron · ESTUN · INOVANCE and more — see the complete alarm code hub.

Frequently asked questions

QWhat does the NACHI e0044 alarm mean?

The motor supply DC bus voltage is too high, usually from regenerative energy not being dissipated. This fault appears in a large share of our Nachi AW / FD series service tickets, and the first round of on-site checks usually finds the source. NACHI e0044 sits in the drive & power stage family; on our work orders the highest-frequency trigger for this code is "Faulty or missing regenerative resistor".

QCan I clear a NACHI e0044 alarm myself?

Whether NACHI e0044 clears on its own depends on the outcome of "Check the regenerative resistor and circuit". Finish the flow with "Retest at lower speed" to confirm NACHI e0044 - do not skip it. If that step is clean, the second most frequent cause on NACHI e0044 is "Aggressive deceleration with high inertia". Two attempts and still there means stop: NACHI e0044 involves the DC bus and power stage, and running NACHI e0044 on can turn a repairable fault into a replacement.

QFor drive/power alarms like NACHI e0044, what spares do you bring on site?

The commonest causes we see on NACHI e0044 are "Faulty or missing regenerative resistor, Aggressive deceleration with high inertia, Incoming supply too high", so we stock the van against those. For NACHI e0044 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 NACHI e0044, drive alarms usually stop the whole line, so they sit at the front of our dispatch queue. Before we roll, tell us what NACHI e0044 shows on the pendant error-code screen (E-series codes) with amplifier panel indicators and what the machine was doing - phone or video triage is free.

The content on NACHI e0044 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 Nachi documentation, or contact us to confirm. Henghuan is an independent service provider with no affiliation or endorsement by Nachi.