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Input energy / auxiliary supply

Danfoss VLT 2900 Auxiliary Supply and DC-Link Path

Energy path for compact Danfoss cases where DC-link undervoltage, display instability or power-board suspicion must be separated from input fuses, rectifier, DC link and auxiliary supply behavior.

Circuit path9 min read

Scope of this technical record

Input, DC-link and auxiliary supply route for compact Danfoss VLT 2900 power-board and display instability cases.

Safety boundary

High voltage remains after disconnection. Verify discharge before measurements or board removal.

VLT 2900 DC-link / auxiliary route

1Input
→
2Rectifier
→
3DC link
→
4Aux supply
→
5Loads

DC-link evidence comes before display, driver or board decisions.

DC link before control conclusions

Many symptoms that look like a failed control board begin with missing or unstable DC-link energy. The route documents line input, protection, rectifier, DC link and auxiliary supply behavior before low-voltage or gate-driver conclusions.

This path also helps decide whether a donor compact drive is appropriate: if the incoming supply or load is the true cause, a replacement drive is at risk.

Field record checklist

  • Line input
  • Protection state
  • DC-link rise
  • Auxiliary supply behavior
  • Display/fan behavior
  • Warning 8 timing

Technical basis and reference documents

This is an independent editorial technical reference. Original manufacturer documentation remains controlling for installation, repair and commissioning decisions.

Danfoss service tips for VLT alarm boundariesDanfoss

Confirms Alarm 13 overcurrent, Alarm 14 earth fault, Alarm 16 current short circuit, input-phase and DC-link alarm boundaries used to structure the first service routes.

VLT 2800 Series instruction manualDanfoss

Documents VLT 2800 warning and alarm text including Alarm 13 peak current, Alarm 14 ground fault, Alarm 15 switch-mode supply and Alarm 16 short-circuit cautions.

Danfoss earth-fault service notesDanfoss

Provides practical Alarm 14 separation between motor/cabling evidence and drive-side current-sensor evidence, including no-motor current observations and manual-initialization caution.

Evidence intake

Turn this record into a qualified service request

A repair decision is much more reliable when the request includes the exact identity of the drive, the first fault evidence and the machine condition when the symptom appeared.

  • Complete drive type code / MLFB or nameplate model
  • Fault code, fault value and first event before reset
  • When the event appears: power-up, enable, ramp, run, decel or stop
  • Motor/cable connected or isolated during the symptom
  • Visible board, option-card, module and connector identifiers
  • Previous repair history, replacement parts and repeat-failure pattern
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