AC drives / compact VFDs and legacy drive repair
Technical records for Danfoss VLT drives, including FC-series service routes and compact VLT 2800 / 2900 control-power, output-fault, gate-driver and board-evidence paths.
Scope of this technical record
Danfoss VLT coverage is sharpened around FC-series field cases 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
Danfoss VLT evidence required
Danfoss VLT users checking 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-service map
| Service case | 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.
Available series
VLT 2800 / 2900 service hub for compact-drive cases where a blinking display, DC-link undervoltage, Alarm 13 overcurrent, Alarm 14 earth fault or Alarm 16 short circuit must be separated into control supply, external motor/cable, current feedback, gate-driver and power-board evidence.
Danfoss VLT service hub for routing Alarm 14 earth fault, Alarm 16 short circuit, Alarm 4 mains phase loss, Alarm 29 heatsink temperature and DC-link overvoltage through field evidence before drive-side repair decisions.
Danfoss VLT coverage is organised as small service clusters. The latest brake/DC-link cluster separates high incoming line voltage, regenerative deceleration energy, brake-resistor duty, brake-chopper command and DC-link sensing before an Alarm 7 or overvoltage case becomes a board-repair request.
Danfoss VLT coverage starts with FC-series service routes that technicians commonly check: alarm 14 earth fault, alarm 16 short circuit, alarm 4 mains phase loss, overvoltage during deceleration and alarm 29 heatsink temperature.
Danfoss VLT 2800 and VLT 2900 coverage links common alarms such as DC-link undervoltage, overcurrent, earth fault and internal short-circuit symptoms to the reviewed CB and DB drawing sets for control supply, I/O and gate-driver evidence.
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