Scope of this technical record
Cross-brand VFD Fault Triage organizes common AC drive symptoms into safe diagnostic boundaries for qualified maintenance and repair personnel.
This framework is not a live-repair procedure. Industrial VFDs contain hazardous input, DC-link and output-stage energy; isolation, discharge verification and qualified site procedure are mandatory.
Why cross-brand VFD symptoms need a database path
Many service searches start with a symptom rather than a complete model number: no display, overcurrent at startup, DC bus overvoltage during deceleration, ground fault on run or repeated IGBT failure after repair. The wording varies by manufacturer, but the diagnostic boundary is often similar enough to create a structured first-pass route.
The value of this track is not to replace the OEM manual. It prevents the most expensive early mistake: jumping from a visible alarm to a replacement board or module before line supply, precharge, DC-link energy, control power, motor cable, braking hardware and gate-driver evidence are separated.
Symptom-to-boundary map
The first question is not which component failed. The first question is which boundary must be proven. A dark keypad points to input, DC-link and auxiliary supply evidence; an instant overcurrent trip points to output cable, load, parameters, driver and current sensing; a deceleration overvoltage points to regenerated energy and braking capacity.
Cross-brand VFD triage map
| Symptom | First diagnostic boundary | Common mistake to avoid |
|---|---|---|
| No display | Input / precharge / DC link / SMPS | Replacing the keypad before supply evidence |
| Overcurrent at startup | Motor cable / load / driver / current feedback | Resetting repeatedly into a damaged bridge |
| DC bus overvoltage on stop | Ramp / braking / regeneration / bus feedback | Shortening decel without braking capacity |
| Ground fault at run | Motor insulation / cable / output accessories | Megger testing through drive electronics |
| Repeated IGBT failure | Gate drive / isolated supply / snubber / load | Installing a second module without driver checks |
How to use this record for service requests
A useful request should include the exact model, input voltage class, frame size, fault text, when the trip occurs, whether the motor was connected, any previous repair, photos of labels and visible board identifiers. Without those details, a generic symptom stays generic and cannot become a high-confidence model record.
This track also creates internal links from generic symptoms into brand-specific pages. When a user later provides an ABB ACS800, Siemens MASTERDRIVES, Parker 590P, Yaskawa A1000 or Schneider ATV unit, the generic route can be narrowed into a manufacturer-specific fault page.
Field record checklist
- Complete drive manufacturer and model number
- Input voltage class and approximate power/frame size
- Exact fault code or keypad wording
- When the symptom appears: power-up, enable, acceleration, deceleration or load
- Motor/cable connected or disconnected status under approved procedure
- Photos of nameplate, control board, power board and visible damage
- Any recent module, capacitor, fan, board or parameter repair
Technical basis and reference documents
This is an independent editorial technical reference. Original manufacturer documentation remains controlling for installation, repair and commissioning decisions.
Internal database framework derived from common industrial AC drive architecture and field-triage patterns.
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.
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.