Scope of this technical record
Maps the PowerFlex input, rectifier, precharge, DC-link and dynamic-braking route used by F4 undervoltage and F5 overvoltage cases.
DC-bus and input measurements require qualified live-work controls. Verify discharge before internal access.
PowerFlex input / DC-bus path
The same energy path explains F4 undervoltage and F5 overvoltage from opposite directions.
PowerFlex input DC-bus path image
Two opposite faults, one energy route
F4 and F5 appear opposite, but both travel through the same energy path. F4 asks whether enough energy reaches and remains in the DC link. F5 asks whether too much energy is being forced into the DC link or whether the brake path cannot dissipate it.
The circuit-path record keeps input supply, precharge, capacitor bank, bus measurement, brake transistor and resistor evidence in one place.
Energy-path matrix
Measure at the point that corresponds to the symptom instead of replacing the easiest board.
PowerFlex input and DC bus route
| Node | F4 relevance | F5 relevance |
|---|---|---|
| L1/L2/L3 input | Sag/missing phase | High line/transient |
| Fuses/contactor | Open pole or loose connection | Switching transient |
| Precharge/rectifier | Weak bus rise | Charging anomaly |
| DC-link capacitors | Low storage/ripple | Bus feedback integrity |
| Brake chopper/resistor | Usually not primary | Regenerated-energy dissipation |
Field record checklist
- Input line evidence
- Bus charge behaviour
- Precharge evidence
- Brake path
- Load-inertia context
Technical basis and reference documents
This is an independent editorial technical reference. Original manufacturer documentation remains controlling for installation, repair and commissioning decisions.
OEM installation and safety context for input/output power handling.
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