What the Er.920 alarm means

Regenerated energy during deceleration exceeded the braking resistor's rated capacity; the drive trips to protect the bus capacitors. We are very familiar with this alarm on INOVANCE IRCB500 / IRCB501 + SV660 servo systems — usually the first on-site inspection is enough to confirm the cause.

Most common causes

  • Deceleration too fast for the moving mass
  • Resistor capacity parameter set too low
  • Resistor aged and resistance drifted high
  • Overhauling load on a vertical axis
Field note: Our ticket data shows the first cause is by far the most common — start there to avoid dead ends.

Step-by-step field fix

  1. Measure the resistor and compare to specification
  2. Match the regenerative parameter to the real resistor
  3. Soften deceleration or reduce payload
  4. Fit a larger external resistor for high-duty applications
  5. Check vertical-axis brake and counterbalance settings
Safety first: For INOVANCE er-920, 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 resistor and compare to specification; anything past that falls under the DC bus and power stage and needs a certified engineer. On INOVANCE er-920: 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

INOVANCE er-920 belongs to the drive & power stage family. On INOVANCE er-920 the failing stage is Inovance servos (SV660N class), same family as the robot controller on the Inovance robot controllers (IRCB series and kin) - the fault sits on the energy chain: mains input, rectification, DC bus, braking resistor, inverter power devices and the drive board. We start reading INOVANCE er-920 at the pendant alarm screen (ER.xxx / 0x9xxx segments) and the servo panel Er code.

The chain involved in INOVANCE er-920 runs: three-phase mains -> rectifier -> DC bus (bus capacitors) -> brake chopper / braking resistor -> inverter (IGBT) -> motor.

Bottom line up front: Deceleration too fast for the moving mass is the first suspect for INOVANCE er-920, 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 INOVANCE er-920 (Regenerative Overload); written by the Henghuan repair team, updated 2026-10-01.

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Related Drive & Power Stage alarms

Er.201 — Hardware Overcurrent Er.210 — Motor Overload Er.400 — Main Circuit Overvoltage Er.410 — Main Circuit Undervoltage Er.610 — Drive Overload (I2t)
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 EFORT · JAKA · AUBO and more — see the complete alarm code hub.

Frequently asked questions

QWhat does the INOVANCE er-920 alarm mean?

Regenerated energy during deceleration exceeded the braking resistor's rated capacity; the drive trips to protect the bus capacitors. We are very familiar with this alarm on INOVANCE IRCB500 / IRCB501 + SV660 servo systems — usually the first on-site inspection is enough to confirm the cause. INOVANCE er-920 sits in the drive & power stage family; on our work orders the highest-frequency trigger for this code is "Deceleration too fast for the moving mass".

QCan I clear a INOVANCE er-920 alarm myself?

Whether INOVANCE er-920 clears on its own depends on the outcome of "Measure the resistor and compare to specification". Finish the flow with "Check vertical-axis brake and counterbalance settings" to confirm INOVANCE er-920 - do not skip it. If that step is clean, the second most frequent cause on INOVANCE er-920 is "Resistor capacity parameter set too low". Do not chase takt through a repeating INOVANCE er-920. Left alone, drive & power stage faults tend to graduate from repairable to must-replace.

QFor drive/power alarms like INOVANCE er-920, what spares do you bring on site?

The commonest causes we see on INOVANCE er-920 are "Deceleration too fast for the moving mass, Resistor capacity parameter set too low, Resistor aged and resistance drifted high", so we stock the van against those. For INOVANCE er-920 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 INOVANCE er-920, drive alarms usually stop the whole line, so they sit at the front of our dispatch queue. Before we roll, tell us what INOVANCE er-920 shows on the pendant alarm screen (ER.xxx / 0x9xxx segments) and the servo panel Er code and what the machine was doing - phone or video triage is free.

This page on INOVANCE er-920 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 INOVANCE documentation or contact us. Henghuan is an independent service provider, not affiliated with or endorsed by INOVANCE.