IndustrialDriveDataDrive Board & Diagnostic Database
Diagnostic workflow

Emerson TD900 POFF Display Investigation

Entry symptom: POFF is displayed at power-up or appears only after a run command.

Safety controls before proceeding
  • Do not infer that POFF is harmless; abnormal bus or supply conditions can coexist with damaged power components.
  • Discharge the DC bus before offline inspection of capacitors, connections or transformer areas.

Investigation sequence

1

Classify the occurrence

Separate immediate POFF after power-up from POFF appearing under motor operation.

2

Check the drive-board detection area

Inspect the local voltage-sensing path, capacitors and ribbon connection condition.

3

Inspect load-related behavior

For run-only POFF, include the drive-board transformer and stressed supply behavior in the investigation.

4

Prevent repeat damage

Do not repeatedly cycle power or run commands before addressing suspected damaged capacitors or power components.

Stop conditions

  • Bulged or vented DC-link capacitor
  • Suspected rectifier/IPM damage
  • Abnormal DC-bus behavior

Linked records

POFF
Input Undervoltage / Drive-Board Supply Indication

A POFF indication may be associated with an undervoltage condition or with an abnormal drive-board sensing/supply path. A run-only POFF observation can point toward a different stress condition than a power-up POFF observation.

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