Scope of this technical record
Repeat IGBT/IPM failure after replacement in an industrial VFD output stage.
Repeat semiconductor failure can be explosive and arc-flash hazardous. This page is a repair-planning record, not an energized test method.
Repeat IGBT failure route
Another module is a stop condition until driver, bus and external-load evidence is reconciled.
Repeated IGBT failure pre-power map
Why replacement modules fail again
A failed IGBT or IPM is often the visible casualty, not the only failed part. The original event may have damaged gate drivers, isolated supplies, current sensors, snubber components or feedback protection. It may also have been caused by a motor cable or load fault that is still present.
The practical repair rule is simple: do not fit another expensive module until the driver path, DC-link stress path and external output path have been reviewed.
Pre-power evidence package
A proper repair request should document each phase leg, gate resistor condition, driver IC or optocoupler area, isolated supply condition, current-feedback path, bus capacitor condition and motor/cable status. The goal is to make the next energization a controlled verification, not a destructive experiment.
Repeat-failure evidence checklist
| Area | Why it matters | Decision |
|---|---|---|
| Gate driver | Can command both devices incorrectly or fail to turn off | Repair before module power-up |
| Isolated supply | Weak or missing gate voltage overheats module | Verify before load test |
| Snubber / clamp | Excess voltage stress can puncture devices | Inspect with bus components |
| Current sensing | May false trip or fail to protect | Check against fault history |
| Motor cable | External short can destroy a good module | Verify before service return |
Stop conditions before another module is installed
Any missing isolated driver rail, mismatched gate resistor, damaged clamp component, biased current-feedback channel, burned bus component or unresolved motor/cable fault is a stop condition. In those cases the right next step is not another module purchase; it is a controlled repair review.
Field record checklist
- Original failure mode
- Module part number and installation history
- Gate-driver board photos
- Isolated supply evidence
- Snubber/current-sensor evidence
- Motor cable and load condition
Technical basis and reference documents
This is an independent editorial technical reference. Original manufacturer documentation remains controlling for installation, repair and commissioning decisions.
Linked workflow for repair-risk isolation.
Diagnostic workflow
Replacement IGBT, IPM or output module fails again during power-up, enable or early load testing.
Overcurrent trip appears immediately at run command, during acceleration or before stable speed is reached.
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