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What to Record Before Resetting a Tripping VSD
A tripping VSD is telling a story. If the drive is reset straight away, the most useful part of that story can disappear.
One reset may be reasonable after a known one-off event. Repeated resets are different. They can hide an overload, a cooling problem, a failing bearing, poor supply conditions, incorrect acceleration settings, or a process change that is pushing the motor beyond its normal duty.
Before pressing reset, take a short pause and record what the drive, motor, and process were doing at the time of the trip. The goal is not to diagnose everything on the spot. The goal is to protect the evidence so the problem can be investigated in a structured way.
Always follow site procedures and electrical safety rules. If the VSD is in a live panel, only competent and authorised people should inspect it. Do not open covers, bypass interlocks, or restart equipment unless it is safe to do so.
Why resetting first makes troubleshooting harder
Most VSDs store some fault information, but that does not mean every useful detail will be easy to find later. Some drives only show the latest trip. Others keep a log but not the surrounding process conditions. Older units may show a code without a time stamp. Some faults get overwritten after more resets.
A trip code also rarely tells the full story on its own. An overcurrent fault might come from a jammed pump, a motor insulation issue, a short acceleration time, poor tuning, or an intermittent mechanical load. An overtemperature fault might point to a hot switchroom, blocked heatsink, failed cooling fan, or excessive switching caused by the application.
The VSD sees electrical symptoms. The cause may sit somewhere else.
That is why the notes taken before reset matter. They connect the drive’s fault data with real operating conditions, such as the load, speed, process demand, and timing of the event.
A fault code tells you what the drive detected. The surrounding observations help explain why it detected it.
Record the exact fault information before anything changes
Start with the information that may vanish or change after reset. Photograph the keypad or HMI if site rules allow it. A clear photo is often better than a rushed handwritten note.
Capture the full fault code and wording, not just a general description. For example, write down the exact text shown on the display, such as `OC`, `Overcurrent`, `DC bus overvoltage`, `Motor overload`, or `Heatsink overtemperature`. Different manufacturers use similar words in different ways.
Also record the drive state. Was it running, accelerating, decelerating, stopped, or trying to restart? A trip during acceleration points the investigation in a different direction from a trip at steady speed.
Useful fault details include:
What to record | Why it helps |
Fault code and message | Identifies what the drive detected |
Date and time | Helps match the trip to process events, shifts, weather, or supply disturbances |
Drive status at trip | Shows whether the fault occurred during start, stop, speed change, or steady running |
Last command source | Confirms whether the command came from keypad, PLC, remote I/O, fieldbus, or local control |
Active warnings | Warnings can appear before the final trip |
Fault history position | Shows whether the same trip is repeating or faults are changing |
Reset count or recent resets | Helps separate a new event from an ongoing issue |
If the site uses a SCADA system, PLC trend, or historian, note the exact time so the trip can be cross-checked later. Time accuracy matters. A drive clock that is wrong by several minutes can make matching events harder, so record the actual site time as well.
Capture electrical and motor values at the time of the trip
The load on the motor is one of the most useful clues. If the drive display is still showing pre-trip values, or if the HMI has live and logged readings, write them down before resetting.
Record the motor current in amps and, if available, as a percentage of rated current. Compare it with the motor nameplate full load current and the drive’s configured motor data. A motor drawing more than expected may be overloaded, incorrectly configured, or dealing with a mechanical problem.
Operating speed also matters. A fan or pump at high speed may be close to its load limit. A conveyor at low speed may have poor cooling if the motor relies on shaft-mounted airflow. A mixer may see heavy torque at start-up and less load once product begins moving.
Record these values where possible:
Motor current at trip
Output frequency or speed reference
Actual speed feedback, if fitted
Output voltage
DC bus voltage, if shown
Motor torque or load percentage
Drive temperature or heatsink temperature
Motor thermal model percentage
Input voltage, if displayed
Any current imbalance or earth fault indication
Do not assume the configured motor values are correct. If troubleshooting continues, compare the VSD parameters with the motor nameplate. Incorrect motor current, voltage, power, speed, or overload settings can cause nuisance trips or allow a real overload to run too long.
Note what the process was doing
A drive trip often starts outside the drive. The process may have changed just enough to push the system past its normal operating range.
Before restarting, look at the driven equipment and record what was happening. Was the pump dead-heading against a closed valve? Was a conveyor starting under a heavy load? Was a fan damper in an unusual position? Was a mixer full of cold, viscous product? Was a compressor starting against pressure?
Good process notes are specific. “Pump tripped” is less useful than “Pump tripped 10 seconds after start with discharge valve partly closed and tank level low.”
Record:
Product, material, or fluid being handled
Valve, damper, gate, or diverter position
Tank level, line pressure, or flow indication
Conveyor loading and any visible blockage
Temperature or viscosity changes in the process
Whether the machine was starting loaded or unloaded
Recent cleaning, maintenance, or changeover work
Any unusual noise, vibration, smell, heat, or movement
For rotating equipment, a quick visual and sensory check can be valuable, as long as it is safe. A pump coupling guard that is and hot, a jammed conveyor roller, or a vibrating fan can steer the investigation quickly.
Do not ignore operators’ observations. They may know that the fault happens only with a certain recipe, only after a washdown, only on hot afternoons, or only when production speed increases. Those details rarely appear in the drive fault log.
Record the timing and pattern of the event
Timing turns isolated notes into a pattern. A VSD that trips three seconds after every start has a different likely cause from one that trips after 40 minutes of running.
Write down when the trip occurred in the operating cycle. If the drive was starting, estimate how far through the acceleration ramp it was. If it was stopping, note whether it was decelerating quickly, coasting, or braking.
Common timing patterns can point towards likely checks.
Trip pattern | Possible lines of investigation |
Trips immediately on start | Short circuit, earth fault, motor cable issue, seized load, incorrect motor data |
Trips during acceleration | Ramp time too short, high inertia load, jammed equipment, torque limit issue |
Trips at steady high speed | Process overload, fan or pump load, motor current limit, supply voltage dip |
Trips during deceleration | DC bus overvoltage, braking resistor fault, decel time too short, high inertia load |
Trips after long running | Cooling problem, ambient temperature, motor overload model, bearing or mechanical drag |
Trips at random times | Loose connection, intermittent supply issue, wet cable, control signal problem |
The pattern may only become clear after several recorded events. That does not mean resetting repeatedly without thought. It means building a controlled record while following site rules and deciding when to stop and isolate the equipment.
If the trip protects a critical process, the decision to restart may involve operations, maintenance, and safety staff. A clear record supports that decision.
Check the environment around the drive and motor
VSDs need clean airflow and suitable ambient conditions. A drive inside a hot, dusty, or poorly ventilated enclosure may trip even when the motor load is normal.
Before reset, record the condition of the cabinet and surrounding area. Check whether fans are running, filters are blocked, vents are covered, or the enclosure door has been left open as a makeshift cooling method. An open door may cool the drive for a while, but it can also allow dust, moisture, or conductive debris into the panel.
Record these observations:
Cabinet internal temperature, if displayed or measured safely
Drive heatsink temperature, if shown
Cooling fan status
Filter and vent condition
Dust, moisture, corrosion, or chemical exposure
Direct sunlight or nearby heat sources
Switchroom air-conditioning faults
Motor surface condition and cooling path
Motor fan and fan cowl condition
Motor cooling can be just as important as drive cooling. A standard motor running slowly for long periods may not get enough airflow from its own fan. In that case, the motor may overheat even though current looks acceptable for short periods. The notes should show speed, duty cycle, and running time, not current alone.
Include recent changes and maintenance history
Many trips follow a change. The change may be electrical, mechanical, operational, or environmental.
Ask what happened before the first fault. A motor may have been replaced, a gearbox serviced, a pump rebuilt, a belt tensioned, or a new recipe introduced. Someone may have changed a parameter to fix a different issue. A valve may have been replaced with one that behaves differently. A production target may have increased.
Record recent changes such as:
Motor, cable, gearbox, pump, fan, or conveyor work
Parameter changes in the VSD
PLC or HMI changes affecting speed commands
Sensor replacement or recalibration
Process recipe or product changes
Cleaning or washdown near motor terminals
Power supply work or generator operation
New equipment added to the same supply
If the VSD has parameter backup files, note the current parameter set version or backup date. If there is no backup, that becomes part of the follow-up. Parameter drift over time can make troubleshooting slow, especially when several people have access to the drive.
Use the records to guide the investigation
Once the basic information is captured, the reset decision can be made with better context. If the trip suggests a serious electrical fault, burning smell, damaged cable, water ingress, or unsafe mechanical condition, do not keep resetting. Isolate and investigate.
If a reset is allowed, observe the restart carefully and record what changes. The second event, if it occurs, should add information rather than simply repeat the same failure.
The notes can guide checks in a logical order.
When overload is suspected
Compare recorded motor current with normal running current and nameplate data. Check the driven machine for blockage, drag, high pressure, high flow demand, incorrect valve positions, or increased product load.
For pumps and fans, remember that speed changes can have a large effect on load. A small increase in speed can create a much higher demand. For conveyors and positive displacement equipment, load may relate more directly to material, pressure, or friction.
When acceleration settings are suspected
A drive that trips during ramp-up may be trying to accelerate the load too quickly. Check the acceleration time, current limit, torque boost, motor control mode, and load inertia.
Recording the trip time during acceleration helps. If the drive always trips at the same speed or same point in the ramp, the load profile may be the key.
When cooling is suspected
Look for trips after a long run, on hot days, or when cabinet ventilation is poor. Check drive fans, filters, heatsinks, enclosure temperature, and motor cooling.
A motor running slowly under load may need forced ventilation. The record should show both speed and duration.
When supply conditions are suspected
Input voltage dips, phase loss, imbalance, harmonics, or upstream switching can trigger trips. Record whether other equipment faulted at the same time. Check site trends if available.
Do not assume a supply problem just because the drive reports undervoltage. A contactor, loose terminal, failing isolator, or upstream protection issue can create the same symptom at the drive terminals.
When braking or deceleration is suspected
Overvoltage trips during stopping often relate to regenerated energy from the load. Check deceleration time, braking resistor condition, braking transistor settings, and whether the load is overhauling the motor.
A fan with high inertia or a descending load can feed energy back into the DC bus during deceleration. The trip timing will usually make this clear.
A simple field record template
A short, consistent template helps more than a long report that no one fills in. Use a notebook, maintenance app, or site form. The format matters less than the habit.
Copy this structure and adapt it to suit the site:
Field | Entry |
Equipment name and asset number | |
Drive make, model, and location | |
Motor nameplate current and power | |
Fault code and exact message | |
Date and site time | |
Drive status at trip | |
Speed or frequency | |
Motor current | |
Load or torque percentage | |
DC bus voltage, if available | |
Drive or heatsink temperature | |
Process condition | |
Valve, damper, or load position | |
Unusual noise, vibration, heat, or smell | |
Recent work or changes | |
Weather or room temperature notes | |
Reset attempted | |
Result after reset | |
Person recording details |
This level of detail may feel slow at first. In practice, it often saves time because the same fault is not investigated from scratch after every reset.
Build a habit before the next trip
The best time to prepare is before the drive trips again. Decide what must be recorded, where the information will be stored, and who has authority to reset the equipment. Make sure operators and maintenance staff use the same terms for the same events.
For critical assets, set up trends for motor current, speed, torque, DC bus voltage, drive temperature, and key process values. Even basic trending can show whether a trip is sudden or slowly developing.
A tripping VSD should not be treated as just an annoyance to clear. It is a protective device responding to a condition. Sometimes the cause is simple. Sometimes it is the first sign of a larger fault.
Record the fault code, current, speed, load, timing, environment, and recent changes before resetting. Those few minutes of observation can prevent hours of guesswork, reduce repeat failures, and help decide whether the next safe step is a restart, an adjustment, or a proper shutdown for investigation.
