What the hV alarm means

The servo DC bus voltage is too high — regenerative energy is not being absorbed. This is a high-frequency ticket for our Omron repair team, and on SmartController (ACE / Viper / Cobra) systems one inspection usually identifies the fault.

Most common causes

  • Braking/regeneration circuit fault
  • Aggressive deceleration with high payload/inertia
  • Supply voltage too high
  • Aged bus capacitors
Field note: The top-listed cause has the highest hit rate, so checking it first narrows things down fast.

Step-by-step field fix

  1. Check the regeneration/braking resistor circuit
  2. Reduce deceleration rates on fast moves
  3. Verify the incoming supply voltage
  4. Check payload settings
  5. Power-cycle and retest; replace the regeneration hardware if the fault persists
Safety first: For OMRON hv, 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 regeneration/braking resistor circuit; the DC bus and power stage handling is not a DIY job. On OMRON hv: 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

OMRON hv belongs to the drive & power stage family. On OMRON hv the failing stage is integrated drive units (amplifier and supply in one housing) on the OMRON robot controllers (including SCARA and cobot companions) - the fault sits on the energy chain: mains input, rectification, DC bus, braking resistor, inverter power devices and the drive board. We start reading OMRON hv at controller status indicators and the software error list (letter prefixes RC / SW / V / M / D / A / E).

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

When OMRON hv fires, the site usually reports Braking/regeneration circuit fault 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 OMRON hv (High Voltage Bus Fault); written by the Henghuan repair team, updated 2026-10-01.

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Related Drive & Power Stage alarms

D# (-1021) — Duty Cycle Exceeded (Joint N) 24 — 24V Supply Fault A# — Amplifier Fault (Joint N) h# — High Temperature — Amplifier (Joint N)
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 ESTUN · INOVANCE · EFORT and more — see the complete alarm code hub.

Frequently asked questions

QWhat does the OMRON hv alarm mean?

The servo DC bus voltage is too high — regenerative energy is not being absorbed. This is a high-frequency ticket for our Omron repair team, and on SmartController (ACE / Viper / Cobra) systems one inspection usually identifies the fault. OMRON hv sits in the drive & power stage family; on our work orders the highest-frequency trigger for this code is "Braking/regeneration circuit fault".

QCan I clear a OMRON hv alarm myself?

Whether OMRON hv clears on its own depends on the outcome of "Check the regeneration/braking resistor circuit". Finish the flow with "Power-cycle and retest; replace the regeneration hardware if the fault persists" to confirm OMRON hv - do not skip it. If that step is clean, the second most frequent cause on OMRON hv is "Aggressive deceleration with high payload/inertia". After clearing OMRON hv, 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 OMRON hv, what spares do you bring on site?

The commonest causes we see on OMRON hv are "Braking/regeneration circuit fault, Aggressive deceleration with high payload/inertia, Supply voltage too high", so we stock the van against those. For OMRON hv 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 OMRON hv, drive alarms usually stop the whole line, so they sit at the front of our dispatch queue. Before we roll, tell us what OMRON hv shows on controller status indicators and the software error list (letter prefixes RC / SW / V / M / D / A / E) and what the machine was doing - phone or video triage is free.

This page on OMRON hv was compiled from actual repair records of the Henghuan Robotics repair team. Alarm notes are our own summary for troubleshooting reference only and may vary with controller and software version — please consult Omron documentation or contact us if in doubt. Henghuan is an independent service provider, not affiliated with or endorsed by Omron.