Allen-Bradley (Rockwell Automation) PowerFlex 525 fault F004: UnderVoltage
Fault F004 on a PowerFlex 525 is UnderVoltage: the DC bus voltage fell below the drive’s minimum value. Rockwell’s action is to monitor the incoming AC line for low voltage or a power interruption. It is a Type 1 fault, so auto restart can clear it.
Diagnose this with AI
Try Free Drive Diagnostic Upload a keypad photo, the fault history or a parameter export from your Allen-Bradley (Rockwell Automation) PowerFlex 525. InduQT compares the evidence and suggests the next useful checks.
When it happens
- Running at any speed when the supply dips
- During a supply interruption or brownout
- At power-down or when an upstream contactor or disconnect opens
- Stopped/standby if the line sags far enough
Likely causes and checks
1Supply dip or short interruption
- Points to it
- Trip time matches a plant power event; other drives or equipment on the same feeder also reacted.
- Check
- Compare F651 [Fault 1 BusVolts] and the fault time with power-quality or utility records; log the line voltage during the next event.
2Blown input fuse or lost phase
- Points to it
- Trips mostly under load; the drive may also show F003 Power Loss.
- Check
- With the drive isolated, check the input fuses and the line-side connections, then measure all three line-to-line voltages under load.
3Weak supply or undersized transformer
- Points to it
- Trips when large loads start elsewhere on the same supply.
- Check
- Measure the drive input voltage while the large loads start and compare with the drive’s rated input range.
4Upstream switching while the drive runs
- Points to it
- Trips coincide with an input contactor or disconnect opening, or an E-stop that removes line power.
- Check
- Check the control sequence: whether line power is removed before the drive is stopped.
Telling it apart
- F004 is a bus-voltage fault and can be auto-reset (Type 1). F003 Power Loss is Type 2 and points to single-phase operation with excessive load: check input fuses and reduce load.
- Setting A541 [Auto Rstrt Tries] to a nonzero value with A542 [Auto Rstrt Delay] = 0 clears an UnderVoltage fault without restarting the drive, according to the manual.
- If F004 appears every time power is removed, it is the expected result of opening the supply under a run command; fix the sequence rather than the drive.
Relevant parameters
| Parameter | Name | Why it matters |
|---|---|---|
| b005 | [DC Bus Voltage] | Live DC bus voltage; watch it during load changes. |
| F651–F660 | [Fault x BusVolts] | DC bus voltage stored with each of the last 10 faults (PowerFlex 525 only). |
| A541 | [Auto Rstrt Tries] | Number of automatic reset/restart attempts for Type 1 faults (0–9). |
| A542 | [Auto Rstrt Delay] | Time between attempts; 0 with A541 > 0 clears UnderVoltage without a restart. |
Evidence to collect
- b007 and the F631/F641/F651 values at the trip
- Line voltage on all three phases, measured under load
- Input fuse condition
- Plant power events at the same time
- A541/A542 settings
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