Scope of this technical record
Circuit-path reference for technicians diagnosing whether a Yaskawa 616G3-style OC/GF event comes from true output stress, weak gate current, missing negative bias or a protection-feedback fault.
Do not probe live high-voltage switching nodes unless trained and equipped for inverter bench work. The page describes evidence order, not live-test instruction.
616G3 discrete protection path
The page makes the physical protection path visible without redistributing the original schematic.
616G3 discrete driver protection path
Functional route
The route begins with the CPU PWM command, then passes through optocoupler isolation into the gate-current amplifier. Only after the driver can prove it turns the module on and off cleanly should the VCE protection signal be treated as a false board fault.
The fast protection path watches the module voltage drop during the on-command. If the IGBT is not pulled fully on, or if the load current is excessive, the detector can remove the pulse and return an OC/GF signal quickly.
Useful comparison method
The strongest evidence is phase-to-phase comparison.
Channel comparison
| Channel evidence | Healthy expectation | Repair implication |
|---|---|---|
| Gate off-bias | Similar negative bias on all six legs | Missing bias risks shoot-through or false detection |
| Gate on-pulse | Similar amplitude and shape | Weak pulse suggests driver-current problem |
| Protection threshold path | No channel triggers without cause | Unexpected feedback points to detector path |
| Module static result | No short/leakage | Module must be removed from suspicion before board-only claim |
Field record checklist
- Which leg reports or fails
- Output isolation result
- Gate-bias comparison
- VCE detector evidence
- Protection feedback behaviour
Technical basis and reference documents
This is an independent editorial technical reference. Original manufacturer documentation remains controlling for installation, repair and commissioning decisions.
Functional basis for the public route map.