Scope of this technical record
A field-service decision hub for common industrial VFD symptoms that appear across ABB, Siemens, Schneider, Danfoss, Rockwell, Control Techniques, Yaskawa, Fuji, Mitsubishi and compact general-purpose drives.
The hub is for qualified drive-service planning. It does not replace the OEM manual, live-voltage procedure or site lockout/tagout requirements. DC-link capacitors, braking resistors and output modules can remain hazardous after the keypad is dark.
Cross-brand VFD evidence route
Generic VFD pages are organised by evidence order so a dark keypad, OC trip or DC-bus fault does not jump directly to board replacement.
Cross-brand VFD triage map
Why a generic VFD hub can be more useful than a generic checklist
Most public troubleshooting pages list possible causes. A technician still has to decide whether the first boundary is line supply, precharge, DC-link storage, auxiliary control power, gate drive, output current feedback, motor cable insulation, braking hardware or the machine load. This hub is built around that decision order rather than a loose symptom list.
The pages in this batch are deliberately cross-brand because the same practical questions repeat across installed fleets: a dark keypad with line power present, overcurrent at enable, overvoltage on deceleration, ground-fault trips when PWM is applied, output phase loss after repair and IGBT/IPM modules failing again after replacement. Brand-specific pages can then link into the matching path instead of duplicating the same first checks.
Core evidence order
The useful sequence is not code-first. It starts with event timing, then the energy path, then the external motor/cable/load boundary, then board-level evidence. This prevents a dark display from being treated as a keypad, an overcurrent as an automatic IGBT order, or a deceleration overvoltage as a random control-board fault.
Cross-brand VFD triage matrix
| Symptom | First boundary | What moves the case to board-level work |
|---|---|---|
| No display / weak boot | Input, DC link, precharge, auxiliary SMPS | Bus present but low-voltage rails missing, pulsing or collapsed after load isolation |
| Overcurrent at startup | Timing, motor/cable, load, parameter set | Trip remains after external and parameter evidence is clean, or prior module repair is involved |
| Overvoltage during decel | Machine energy, ramp, brake resistor, chopper | Brake path is intact and configured but bus feedback or chopper control remains suspect |
| Ground fault at run | Motor cable, winding insulation, moisture, output accessory | Trip persists with external path proven clear under permitted procedure |
| Repeat IGBT/IPM failure | Driver, isolated supplies, current feedback, bus stress, external load | Any driver/protection defect is unresolved before another module is fitted |
How to use this cluster
Use the fault page when a technician starts from a panel indication. Use the circuit page when the repair team already knows the suspected functional area. Use the diagnostic workflow when a repair shop needs the evidence package before accepting a board or module repair. The same slug family is intentionally linked together so a visitor can move from symptom to measurement path to board boundary.
Field record checklist
- Exact drive brand, model, frame and voltage class
- First fault and whether it appears at power-up, enable, ramp, run, decel or stop
- Motor and cable connected/disconnected status under permitted procedure
- DC-link, precharge and auxiliary power observations
- Photos of power board, control board, gate-driver area and nameplate
- Previous repair history, especially module or capacitor replacement
Technical basis and reference documents
This is an independent editorial technical reference. Original manufacturer documentation remains controlling for installation, repair and commissioning decisions.
Rebuilds the earlier generic workflow and bench-evidence pages on the stable deployment baseline.
Model records
Generic power-stage record for industrial AC drives where incoming supply, rectifier, precharge, DC-link capacitors, braking circuit, gate driver and output bridge must be separated before condemning an IGBT module or control board.
Generic no-display and weak-display record for drives where the keypad, CPU, fan relay, gate-driver supply and feedback circuits depend on auxiliary low-voltage rails derived from the DC bus or an auxiliary input.
Generic DC-link record for overvoltage and deceleration faults where load inertia, ramp time, braking resistor selection, chopper hardware and input supply conditions must be separated.
Fault records
The drive has line power present but the keypad stays dark, flashes briefly, clicks repeatedly or never reaches a ready state.
The drive trips on overcurrent immediately at run command, during initial acceleration or before the motor reaches speed.
The drive runs normally but trips on overvoltage when stopping, ramping down, lowering a load or decelerating a high-inertia machine.
The drive powers up but trips on ground fault, earth fault or leakage indication during enable, acceleration or when output voltage is applied.
The drive reports output phase loss, motor phase loss, unbalanced output current or no torque on one phase.
A replacement output module, IPM or IGBT pack fails during the first power-up, first run test or shortly after returning the drive to service.
Board and assembly records
Generates logic, relay, fan and local electronics supplies from the drive DC bus or auxiliary input.
Transfers PWM command to isolated IGBT/IPM gate signals while providing protection feedback for output-stage faults.
Switches regenerative DC-link energy into a braking resistor when bus voltage exceeds the braking threshold.
Circuit and diagnostic records
Routes incoming three-phase supply through protection, rectification, precharge and DC-link storage before the inverter stage is allowed to run.
Maps the auxiliary supply route that powers the CPU, keypad, I/O, relay logic, fan control and often isolated driver supplies.
Connects PWM command, isolated driver supply, gate components, short-circuit protection and the output bridge to overcurrent and repeat-module-failure symptoms.
Routes excess DC-link energy into braking hardware or controlled overvoltage management during deceleration and overhauling-load events.
Separates motor insulation, cable leakage, terminal contamination, output filters and internal sensing when a drive trips only after output voltage is applied.
Drive line power is present, but the keypad is dark, flashing or repeatedly restarting.
Drive reports undervoltage/precharge fault, blows input fuses or shows no-display symptoms with uncertain DC-link charging.
Overcurrent trip appears immediately at run command, during acceleration or before stable speed is reached.
Drive trips on DC bus overvoltage when stopping, lowering, braking or reducing speed.
Ground fault, earth fault or leakage trip occurs when output voltage is applied.
Replacement IGBT, IPM or output module fails again during power-up, enable or early load testing.
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