Machines Tripping or Resetting
Use this page when machines, control panels, drives, PLCs or process equipment trip, reset, lock out or behave intermittently and the cause is not obvious from spot measurements.
Intermittent machines tripping can be difficult to investigate because the important event may be brief and may happen when nobody is watching. A logger records the electrical conditions before, during and after the problem so that the investigation is based on timed proof.
The correct logger depends on whether the likely cause is voltage dips, high voltage, interruptions, current/load changes, or wider three-phase power behaviour.
What to measure
- The exact time of each trip or reset, compared with recorded electrical events.
- Voltage dips, swells, interruptions and high-voltage periods.
- Current demand and load changes around the event.
- Three-phase voltage and current together where the interaction between load and supply matters.
- Whether the problem repeats at a particular time of day, shift pattern or process stage.
Recommended loggers
| Product | Logger | Best fit | Measures |
|---|---|---|---|
 |
EC-7VAR-RS Electrocorder EC-7VAR-RS Three Phase Voltage, Current & Power Factor Recorder |
Best where both supply voltage and machine load behaviour may be involved. | Three-phase voltage, current, power factor and energy. |
 |
EC-3V Electrocorder EC-3V Three Phase Voltage Recorder |
Best for three-phase voltage complaints, dips, high voltage and voltage imbalance checks. | Three-phase voltage. |
 |
SL-3V Electrocorder SL-3V Compact Three Phase Voltage Recorder |
Useful for compact three-phase voltage investigations where space is limited. | Three-phase voltage. |
 |
EC-2V Electrocorder EC-2V Voltage Logger |
Useful for single-phase voltage behaviour around intermittent faults. | Single-phase voltage. |
Detailed guidance
Why intermittent trips are difficult to diagnose
Poor power quality can cause machines, control panels, drives and power supplies to trip, reset or lock out. The problem is often hardest to diagnose when the machine is unattended, because nobody sees exactly what happened or what the machine was doing at the time.
Power quality is not only something supplied by the electricity network. A customer or neighbouring load can also affect the local voltage supply. Large industrial loads, especially three-phase machinery, can create voltage events and fluctuations that affect other equipment on the same site, or occasionally nearby sites. This page focuses on voltage behaviour rather than frequency distortion, flicker or harmonics.
Start with absolute times
The first question is when the trip or reset happens. If it repeatedly occurs between 02:00 and 04:00, high voltage may be a possibility because voltage and frequency are often higher during off-peak periods. If it occurs during peak loading periods, low voltage may be more likely because voltage and frequency tend to be lower when demand is high.
Accurate event times make the logged data much more useful. The aim is to compare the machine trip time with the voltage, current or power behaviour recorded by the logger.
Look for relative timing
Some problems are linked to another machine or process. Machine A may trip shortly after machine B starts, stops or changes state. That can point to a related loading effect, a voltage dip, or a voltage spike created by switching.
It is also worth considering when the problem does not occur. If machine A never trips when machine C is running, machine C may be absorbing or changing the voltage transients that would otherwise affect machine A.
Consider temperature and process timing
If a trip tends to occur after the machine has been running for a set period, temperature may be part of the cause. Ambient temperature, machine temperature, control-panel temperature or overheating in a power supply can all make an electrical event more likely to cause a shutdown.
Even apparently random faults have a cause. The investigation is about finding the pattern: time of day, load state, process step, temperature, neighbouring equipment or supply event.
Start the electrical investigation at the machine supply
The first logging position is usually as close as practical to the problem machine or control panel. This ensures the logger sees the same voltage events as the equipment. Check whether the supply varies outside the specified limits for the machine, and whether any features of the supply coincide with the trip or reset.
Power supply units can be susceptible to AC voltage problems. They may temporarily fail, shut down to protect themselves, or pass disturbances through to the electronics they are powering. The downstream electronics can then lock up, reset or fail.
Transient duration matters
Very fast high-voltage transients with microsecond durations do not normally cause problems because they contain little energy and are often filtered by suppression components in a good power supply. Transients lasting milliseconds are more troublesome because they contain much more energy and can pass through some suppression circuits.
Voltage drops can also cause problems, particularly if the general AC voltage is already low when the drop occurs. In that situation the effect is compounded and the power supply may drop out.
Set up the logging period
Choose the recording period based on how often the fault occurs. If the trip or reset happens daily, 24 to 48 hours may be enough. If it happens every few days, record for a week or more. With most Electrocorders, a two-minute averaging period gives around 10 days of total recording time.
Program the recorder and connect it to the voltage system as close to the problem machine or panel as possible. When the next trip or reset occurs, download the data and review the average voltages first. If those look acceptable, review the maximum and minimum voltage graphs for each phase.
The maximum and minimum voltage values are resolved to one cycle, which is 20ms at 50Hz or 16ms at 60Hz. If the voltage rises or falls for a full cycle or an appreciable part of a cycle, the Electrocorder will record it and it should be visible in the Vmin or Vmax graphs.
Unless the equipment is unusually sensitive, the AC voltage events that cause problems are often longer than about 5ms and may last for a few cycles. These are the types of fluctuations an Electrocorder voltage or power recorder is designed to capture.
How to approach the investigation
- Record the machine trip time as accurately as possible and compare it with logger timestamps.
- Log long enough to capture normal operation as well as the fault condition.
- Use voltage logging first if the failure looks like a supply event; use combined voltage/current logging if the machine load may be triggering the issue.
- Review repeated events for time-of-day, process-stage or neighbouring-equipment patterns.
Related guides and products
These pages and products give the next level of detail for this application.
Application guides:
- Machine Trip and Reset Loggers: for equipment trips, resets, lockouts and intermittent electrical faults.
- Voltage Problem Loggers: for high voltage, low voltage, voltage variation, dips and interruptions.
- Load Survey and Current Loggers: for feeder checks, current logging, load surveys and capacity planning.
- All application guides: choose an Electrocorder by the job or problem you need to investigate.
Relevant products:
- EC-7VAR-RS: Electrocorder EC-7VAR-RS Three Phase Voltage, Current & Power Factor Recorder.
- EC-3V: Electrocorder EC-3V Three Phase Voltage Recorder.
- SL-3V: Electrocorder SL-3V Compact Three Phase Voltage Recorder.
- EC-2V: Electrocorder EC-2V Voltage Logger.