VLT AC drives / VFDs
Technical records for Danfoss VLT industrial drives, beginning with FC 102 / FC 202 / FC 302 service routes for earth fault, short circuit, mains phase loss, overvoltage and heatsink temperature alarms.
Scope of this technical record
Danfoss VLT coverage is sharpened around FC-series field searches where Alarm 14 earth fault, Alarm 16 short circuit, Alarm 4 mains phase loss, Alarm 29 thermal and DC-link braking events must be separated before a drive is condemned.
Danfoss VLT output and DC-link checks must be performed only after isolation and discharge verification. Do not run insulation tests through the drive or repeat starts into a suspected earth fault.
Danfoss VLT alarm route
Danfoss VLT service pages separate the external output path from sensing and module boundaries.
Danfoss VLT alarm evidence map
What Danfoss searchers need
Danfoss VLT users searching Alarm 14 usually do not need the definition of earth fault. They need to know whether the alarm is caused by the motor, cable, moisture, output module, current sensor or a control/measurement condition.
The most useful Danfoss pages therefore put motor/cabling isolation and current-sensor boundary at the centre of the answer. That is where many public summaries stop too early.
Danfoss VLT repair-intent map
| Search | First split | Evidence | Repair boundary |
|---|---|---|---|
| Alarm 14 earth fault | Motor/cable versus drive-side output or current sensor | Disconnected-output behaviour and insulation evidence | Alarm remains with external path proven clear |
| Alarm 16 short circuit | Phase-to-phase/output module path | Motor cable and output bridge evidence | Static output abnormality |
| Alarm 4 mains phase loss | Line/fuse/contactor before drive | Input measured at drive terminals | Good input but fault remains |
| Alarm 29 heatsink | Cooling, fan, load and thermal interface | Temperature trend and fan evidence | Thermal sensor/power module path |
Field record checklist
- Exact VLT family and type code
- Alarm number and first alarm in queue
- Whether alarm appears with motor connected or disconnected
- Motor/cable insulation evidence
- Output module/current sensor photos where applicable
- Moisture, washdown or thermal pattern
Technical basis and reference documents
This is an independent editorial technical reference. Original manufacturer documentation remains controlling for installation, repair and commissioning decisions.
Used for Alarm 14 motor/cabling versus current-sensor boundary.
Used as public Danfoss support context for persistent earth-fault alarms.