USF: insufficient power supply or transient decrease
ATV320 signals too low network voltage or a transient fall. It is necessary to distinguish the plant event from an internal condition before changing thresholds.
The case in 60 seconds
ATV320 signals too low network voltage or a transient fall. It is necessary to distinguish the plant event from an internal condition before changing thresholds.
Record cycle phase, code, nominal voltage and loads that enter into service at the same time.
The code or symptom directs research, but does not show the fault component alone.
Diagnostic map
Follow the rows in order. Each phase must produce evidence before moving to the next.
| Phase | Controls | Evidence to obtain | Next decision |
|---|---|---|---|
| 01Recognize and collect |
| Event context and complete initial data. | If a data is missing, do not reset to attempts: complete the initial picture first. |
| 02Check and separate hypotheses |
| External causes, configuration, circuit and separate process. | If the data does not match, return to the correct schema and revision before changing parameters. |
| 03Interpret and demonstrate |
| Cause supported by repeatable data and authorized evidence. | If the cause is not proven, stop changes and involve manufacturer, OEM or machine manager. |
Reading and observation
Recognize and collect
- Record cycle phase, code, nominal voltage and loads that enter into service at the same time.
- Check license plate and history without canceling the event or modifying UNDERVOLTAGE MGT.
Event context and complete initial data.
If the result does not matchIf a data is missing, do not reset to attempts: complete the initial picture first.
Qualified technician
Check and separate hypotheses
- Qualified staff: measure the voltages chained in input with appropriate CAT tool and compares imbalance and fall under load.
- Follow the DC bus control manual to the PA/PC points and compare the parameters of the USb- menu with the project.
External causes, configuration, circuit and separate process.
If the result does not matchIf the data does not match, return to the correct schema and revision before changing parameters.
Specialist deepening
Interpret and demonstrate
- Correct the event with network, protections, contactors, section of the cables and transients registered; avoids conclusions from a single vacuum measure.
- After correction repeat the cycle monitored and verify that tension, current and process remain stable.
Cause supported by repeatable data and authorized evidence.
If the result does not matchIf the cause is not proven, stop changes and involve manufacturer, OEM or machine manager.
What to avoid
- Use repeated resets as a diagnostic test.
- Transfer codes, thresholds or parameters from one Drives family to another.
- Change a protection before connecting symptoms, measurement and phase of the cycle.
- PA/PC points are not “safe points”. Internal measures only by qualified personnel, with LOTO procedure, download time and manual size.
When the problem is really solved
The cause of the fall is proven and correct, tensions remain within specification during the real cycle and USF does not recompense.
- The cause is supported by data and not only by the momentary absence of the alarm.
- The cycle that generated the problem has been repeated in authorized conditions.
- Final configuration, measurements and outcome are consistent with applicable machine, drive and documentation.
Applicable documents
Always check size, firmware, options and revision. These sources do not extend the case to other families.
- Primary source of the caseOpen the official source la
- Schneider Electric · Programming and DiagnosticManual · EN · NVE41295 · Official PDF
- Schneider Electric · InstallationManual · EN · NVE41289 · Official PDF