Drive fault or motor fault: what to record

It is 6 a.m., the line is stopped, and the keypad shows a short fault code and little else. The first job is to write down the full text, never the number alone. Manufacturers reuse the same code families for very different events, and the wording is what separates an overcurrent during acceleration from a ground fault, an undervoltage dip, or a motor thermal trip. The same digits can mean different things on different families, which is why a bare number in a note helps nobody.

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The path records what tripped and how the manual defines it. It stops at the protection that acted and does not name a failed component.

On a compact drive like a PowerFlex 4, where the code only lives on the keypad, photograph the display with the message visible. The photo keeps the exact wording even after a power cycle wipes it. This one habit covers the whole class of compact drives whose status display is the only interface, and it costs about as long as reading the code out loud.

The user manuals list fault descriptions alongside the codes, and comparing your recorded text with those lists is a legitimate early step. What it gives you is a definition of the protection that tripped, not a verdict on which part failed. An overcurrent code says the drive measured too much current; it does not say whether the fault is in the drive, the motor, or the load.

Most drives keep a fault history, a dated or sequenced log of recent events, and it is the strongest single clue in the whole intake. One trip after a power dip tells a very different story from the same code landing every shift at the same ramp point. The history turns a single event into a pattern, and patterns are what a later review can actually work with.

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Read the log before anyone clears it. The record preserves recurrence and timing; it does not settle which component failed.

Note whether the fault survives a power cycle, whether it shows up at the same speed or load each time, and whether anything in the process changed just before it started. That timing pattern costs nothing but a minute to record. If the drive lets you export or photograph the log, do that too, so the timing survives the handover instead of living in one person's memory.

The history also bounds the story in the other direction: an empty history on a drive that just failed says the event arrived without warning, and that is worth writing down. Whatever the log shows, capture it before anyone resets and clears it. A cleared fault history is a page torn out of the only book the drive writes.

Write down any settings that were changed recently, even the ones that look harmless. A shortened deceleration ramp, a new setpoint range, or a raised current limit can turn a machine that ran for years into one that trips daily. If the fault appeared after a parameter change, the change itself is evidence, and it belongs in the record with a date and the name of whoever made it.

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The log records what changed and when it changed. It does not prove which change caused the fault, and it does not authorize actuating checks.

Separating process changes from electrical symptoms keeps the repair search from starting in the wrong place. Ask around the shift as well; the person who changed the setting often remembers why, and that reason belongs in the record. A limit that was raised to squeeze through a hard batch is a very different finding from the same limit set during commissioning.

Recent changes also include hardware moves that never reached the drawings: a swapped sensor, a re-routed cable, a new option module. Each one changed the system the drive now protects, and the drive's complaint may be an accurate response to its new world. The intake question is simply what changed, and the answer is cheaper to collect now than to reconstruct later.

With the cabinet open, a handful of seconds-long observations separate a drive that talks from one that does not. A dead display, dark status LEDs, or a cooling fan that never spins each point somewhere different, and none of them requires opening anything or touching a terminal. A drive that powers up and reports a code is behaving very differently from one that shows nothing at all, and that difference shapes the next check.

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The branches are passive observations only. No probing, measurement or component swap is implied, and electrical checks stay with qualified personnel.

Record these observations with the same discipline as the codes: what you saw, on which unit, and when. Photograph the display and the status LEDs, because those shots also document the unit's state before anyone powers it down or moves it. A bench reviewer sees the unit later, in different conditions, and your photos are the bridge between the two moments.

The boundary here is observation, not actuation. Looking at LEDs and displays is safe and reversible; probing, measuring, or swapping components is a different category of work that belongs to qualified personnel with the equipment isolated. The intake record should mark clearly which of those two things happened, so nobody later mistakes a noted observation for a test that was run.

The circuit does not end at the drive terminals, so the record should not either. Put the motor nameplate data on the same page as the drive data: voltage, current, connection diagram, and speed. Those values feed the drive's motor data parameters, so a mismatch between the two nameplates is a finding in itself, and it explains a surprising number of complaints that look like drive faults.

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The match check is a paperwork comparison of printed values. Insulation or live testing is not part of this flow and stays with qualified personnel.

Photograph the motor terminal box and cable routing if you can reach them. The connection diagram matters here, because the same motor draws different current in different connection configurations, and the drive needs the matching values. Leave insulation testing and any live electrical checks to qualified personnel with the equipment isolated, and record that a check is needed rather than guessing at a result.

The motor record also feeds the sizing question later, because a replacement decision has to satisfy the motor that is actually connected. The ten-year-old machine file may not describe the machine that exists today, and the nameplate does. A few minutes at the motor gives the same evidence quality as the drive-side record: dated observations, photos, and honest gaps where nobody looked.

A perfectly healthy drive will protect itself with an overcurrent trip when the load goes wrong. A jammed load, a seized bearing, or a slipping belt can push motor current up until the electronics have no better option than to stop. That is why the mechanical side gets checked before anyone concludes the electronics failed, and the intake is where that possibility gets written down.

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The flow records observations of the load under lockout. It does not include any actuated test, and hand-travel checks follow the machine's own isolation rules.

Ask what the machine was doing when the fault first appeared, and whether the load can be turned by hand with everything locked out. A jam that started during one shift's product change is a different case from a slow decline over months. An overcurrent fault with a mechanical cause gets fixed in the machine, not the drive, which is also the cheapest fix on the list, a good reason to check for it early.

Record what the mechanical check covered and what it could not reach. Nobody expects an intake technician to disassemble a gearbox, and an honest note that the load was checked only by hand-travel still narrows the picture. The point is not completeness but a boundary that the next reader can trust.

Keep the line between observation and verdict visible in the record. A drive can trip because of a motor or cable fault, so a message on the drive's display is not proof that the drive is the broken part. Note what you saw, what was measured and by whom, and what nobody checked at all. That boundary is exactly what lets a later reviewer see where the evidence ends.

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The boundary documents what the intake covered and what it did not. Choosing and running the next check is a separate step for qualified personnel.

A reviewer who can see the boundary can also see which check would move the case forward fastest. The record does its job when the next person can tell the difference between a confirmed measurement, a reported symptom, and an open question. Mixing those three is how a two-line note turns into a wrong repair.

No remote review can settle the diagnosis from this record, and it does not try to. What it does is let a partner decide whether the next step is a motor check, a bench test, or a sizing review, before anything gets shipped anywhere. A request that only says the drive is faulty forces the recipient to start from zero; a dated record with codes, history, motor data, and mechanical notes lets a real decision start with the first reply.

• Write the fault code with its full text, and photograph the keypad before any power cycle.
• Save the fault history with timing, recurrence, and any recent setting changes.
• Log motor nameplate data and mechanical condition on the same record as the drive.
• State what you observed and what you never checked, because a code is not a verdict.

• the drives and VFD hub
• the nameplate reading checklist
• the cabinet environment checklist