What the A.320 alarm means

Regenerative energy from deceleration exceeded the braking resistor capacity; the DC bus voltage keeps rising and the drive alarms out. Our engineers run into this alarm every week on Yaskawa DX100 / DX200 / YRC1000 controllers, and a single on-site inspection usually identifies the problem.

Most common causes

  • Deceleration ramps too aggressive for the payload and inertia
  • Braking resistor undersized for the duty cycle
  • Regenerative resistor degraded (resistance drifted high)
  • Continuous downhill/overhauling load in the program
Field note: In our repair stats the first cause has the highest hit rate, so confirm it first before digging further.

Step-by-step field fix

  1. Measure the braking resistor resistance against specification
  2. Soften deceleration or reduce the payload in the job
  3. Add or upgrade an external regenerative resistor if the duty is inherently high
  4. Check the DC bus voltage trend during the failing move
  5. If hardware is healthy, adjust Pn600 (regenerative capacity setting) to match the installed resistor
Safety first: For YASKAWA a-320, 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. The self-serviceable action is Measure the braking resistor resistance against specification; anything past that falls under the DC bus and power stage and needs a certified engineer. On YASKAWA a-320: 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

YASKAWA a-320 belongs to the drive & power stage family. On YASKAWA a-320 the failing stage is Yaskawa Sigma-series servo drives (servo packs) assigned per axis in the cabinet on the DX100 / DX200 / YRC1000 / YRC1000micro - the fault sits on the energy chain: mains input, rectification, DC bus, braking resistor, inverter power devices and the drive board. We start reading YASKAWA a-320 at the pendant alarm list (A / E / 4xxx segments) together with the servo drive's digit display.

The chain involved in YASKAWA a-320 runs: three-phase mains -> rectifier -> DC bus (bus capacitors) -> brake chopper / braking resistor -> inverter (IGBT) -> motor.

Bottom line up front: Deceleration ramps too aggressive for the payload and inertia is the first suspect for YASKAWA a-320, 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 YASKAWA a-320 (Regenerative Overload); written by the Henghuan repair team, updated 2026-10-01.

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Related Drive & Power Stage alarms

A.100 — Overcurrent or Heat Sink Overheated (SERVOPACK) A.400 — Overvoltage — Main Circuit DC Voltage Too High A.410 — Undervoltage — Main Circuit DC Voltage Too Low A.710 — Overload — High Load (Stall-level Torque) A.720 — Overload — Low Load (Continuous Over-torque) A.7A0 — Heat Sink Overheated (>100 degC)
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 Universal Robots · Kawasaki · Staubli and more — see the complete alarm code hub.

Frequently asked questions

QWhat does the YASKAWA a-320 alarm mean?

Regenerative energy from deceleration exceeded the braking resistor capacity; the DC bus voltage keeps rising and the drive alarms out. Our engineers run into this alarm every week on Yaskawa DX100 / DX200 / YRC1000 controllers, and a single on-site inspection usually identifies the problem. YASKAWA a-320 sits in the drive & power stage family; on our work orders the highest-frequency trigger for this code is "Deceleration ramps too aggressive for the payload and inertia".

QCan I clear a YASKAWA a-320 alarm myself?

Whether YASKAWA a-320 clears on its own depends on the outcome of "Measure the braking resistor resistance against specification". Finish the flow with "If hardware is healthy, adjust Pn600 (regenerative capacity setting) to match the installed resistor" to confirm YASKAWA a-320 - do not skip it. If that step is clean, the second most frequent cause on YASKAWA a-320 is "Braking resistor undersized for the duty cycle". After clearing YASKAWA a-320, 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 YASKAWA a-320, what spares do you bring on site?

The commonest causes we see on YASKAWA a-320 are "Deceleration ramps too aggressive for the payload and inertia, Braking resistor undersized for the duty cycle, Regenerative resistor degraded (resistance drifted high)", so we stock the van against those. For YASKAWA a-320 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 YASKAWA a-320, drive alarms usually stop the whole line, so they sit at the front of our dispatch queue. Before we roll, tell us what YASKAWA a-320 shows on the pendant alarm list (A / E / 4xxx segments) together with the servo drive's digit display and what the machine was doing - phone or video triage is free.

This page on YASKAWA a-320 was 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 Yaskawa documentation or contact us. Henghuan is an independent service provider, not affiliated with or endorsed by Yaskawa.