What the E0038 alarm means

The motor ran above its thermal limit for the duty cycle; a thermal overload trip protects the motor. We fix this Nachi AW / FD series fault almost daily, and one round of on-site checks usually confirms what is going on.

Most common causes

  • Excessive payload
  • High duty cycle
  • Mechanical drag
  • Wrong motor/inertia parameters
Field note: We have tallied real cases: the first cause tops the list, so start your diagnosis there.

Step-by-step field fix

  1. Verify the payload
  2. Lower the duty cycle
  3. Check for mechanical drag
  4. Confirm motor parameters
  5. Let the motor cool and retest
Safety first: For NACHI e0038, 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: Verify the payload. Beyond that it is the DC bus and power stage work - leave it to a professional. On NACHI e0038: 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 e0038 belongs to the drive & power stage family. On NACHI e0038 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 e0038 at the pendant error-code screen (E-series codes) with amplifier panel indicators.

The chain involved in NACHI e0038 runs: three-phase mains -> rectifier -> DC bus (bus capacitors) -> brake chopper / braking resistor -> inverter (IGBT) -> motor.

Bottom line up front: Excessive payload is the first suspect for NACHI e0038, but read it along the energy chain: Any link on this chain dropping voltage shows up at the end as a drive alarm, so order matters. We measure the mains first: more than 3% phase imbalance is enough to sag the bus under load, and plenty of bus over/under-voltage alarms are actually a grid problem wearing a robot costume. Mains fine, then the bus capacitors - bulged cases, weeping electrolyte or a lifted vent mean replacement; capacitance down 20% or more cannot hold the bus during braking. Last, the braking resistor: healthy values sit in the tens of ohms depending on rating, and an open or drifted resistor trips regenerative overvoltage directly.

Field notes on this page cover NACHI e0038 (Overload); written by the Henghuan repair team, updated 2026-10-01.

If you can't fix it, reach our engineers directly

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Related Drive & Power Stage alarms

E0028 — Motor Power Voltage Drop E0032 — Overcurrent E0042 — Motor Temperature Rise Abnormal E0044 — Motor Power Overvoltage
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 e0038 alarm mean?

The motor ran above its thermal limit for the duty cycle; a thermal overload trip protects the motor. We fix this Nachi AW / FD series fault almost daily, and one round of on-site checks usually confirms what is going on. NACHI e0038 sits in the drive & power stage family; on our work orders the highest-frequency trigger for this code is "Excessive payload".

QCan I clear a NACHI e0038 alarm myself?

Whether NACHI e0038 clears on its own depends on the outcome of "Verify the payload". Finish the flow with "Let the motor cool and retest" to confirm NACHI e0038 - do not skip it. If that step is clean, the second most frequent cause on NACHI e0038 is "High duty cycle". After clearing NACHI e0038, watch it for one shift. A second trip means stop and let an engineer arrive with the right test gear for the DC bus and power stage.

QFor drive/power alarms like NACHI e0038, what spares do you bring on site?

The commonest causes we see on NACHI e0038 are "Excessive payload, High duty cycle, Mechanical drag", so we stock the van against those. For NACHI e0038 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 e0038, drive alarms usually stop the whole line, so they sit at the front of our dispatch queue. Before we roll, tell us what NACHI e0038 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 notes on NACHI e0038 were summarized by the Henghuan Robotics repair team from on-site service. The alarm interpretation is our empirical summary for troubleshooting reference and may vary by controller and software version — please check Nachi documentation or contact us with questions. Henghuan is an independent service provider, not affiliated with or endorsed by Nachi.