As critical manufacturing processes become more sophisticated, so do the motor control systems behind them increase in complexity. As such, it is more important than ever to keep these critical assets running at peak performance as not only is equipment failure expensive, but the cost of lost production from waiting on replacement parts or for electric motor rewind services will also be high. Seeing as motor failure can lead to all sorts of electrical and mechanical issues, it is essential to consider both when conducting any troubleshooting procedures. Moreover, by prioritising workloads and running preventive maintenance regularly, facilities can better mitigate the odds of unexpected motor failures caused by normal system operating stresses.
Below, we cover the four fundamental steps to preventing such untimely failures in electric motors.
1. Gather initial data about the motor condition and specifications at installation
The first and foremost step in motor failure prevention is capturing initial asset data. This includes the machine’s specifications, performance tolerance ranges, and operating conditions at the time of installation. Having this information establishes a baseline on how the motor is supposed to run, and it becomes easier to detect any deviations from the original installation as you conduct regular preventive checks.
Not only that, it also allows one to catch potential issues stemming from improper installation before they cause motor failure. While all mechanical equipment experiences wear, improper installation accelerates the process and causes it to break down sooner. Therefore, proper installation lays the foundation for a motor’s service life and sometimes extends it.
Before turning on a motor for the workday, take care to check for problems like:
- Shaft voltage: exceeding the bearing grease’s insulating capacity results in flashover currents to the outer bearing
- Pipe strain: forces and stresses acting on the rest of the motor may transfer backwards into the machine
- Soft foot: unevenness in the motor’s mounting feet
2. Draw up and stick to your preventive maintenance schedule
Upon capturing all the motor data, next will be establishing a regular preventive maintenance schedule designed not only for upkeep but also for tracking the operating conditions of all motors in the facility. On each round of maintenance, make it a habit to compare the new measurements against the initial motor specifications and tolerances to identify potential anomalies. Also, consider adding thermal imaging to your testing regimen to determine the heat output of the motors and other related assets. Such tools allow for immediate verification of whether they are running too hot or too cold than usual, which may indicate an issue that warrants immediate attention.
But regardless of any strict and timely maintenance, a few mechanical issues may still surface down the line since time always wears down everything eventually. That being said, motors will last longer thanks to the regular upkeep and early resolution of mechanical issues before they become a bigger problem, eliminating the need for replacements for a long time.
Some of these common mechanical issues include:
- Bearing wear: occurs when surfaces slide against one another due to insufficient lubrication to keep them apart
- Misalignment: this generally means that the motor drive shaft is not perfectly aligned with the load
- Shaft looseness: caused by too much between the stationary and rotating elements inside a motor
- Shaft imbalance: the centre of a rotating component is not placed perfectly on its rotational axis
Many breakdowns born from mechanical issues generally manifest first as vibration. Therefore, incorporating a vibration sensor system into your operators’ toolset can help catch many such problems before they result in motor failure.
3. Establish a baseline by storing and recording individual measurements
When performing preventive maintenance, save any thermal images and measurements taken during the procedure, as they can be used to create a performance baseline of your facility’s motor assets. Any changes in the trend line that are in excess of 10% to 20% must be investigated immediately to identify the underlying root causes. Most likely, these percent changes in the trend line may not apply to your specific assets, hence the need to determine more suitable numbers based on your system’s performance or asset criticality.
Since a variable frequency drive takes one wave shape and converts it to another, establishing a baseline for a running motor will let you see whenever the output changes.
Using a motor drive analyser allows for quick detection and diagnosis of problems related to VFDs, which commonly include:
- Operational overload
- Sigma currents or stray currents circulating in the motor system
- Reflections on drive output PWM signals caused by a mismatch in the impedance between the load and source
4. Conduct trend analysis
Upon establishing the baseline, continue to track and record measurements periodically, as you can use the gathered data to create an archive as you go. Moreover, it allows for creating a trend analysis that makes it easier for other operators to notice changes in a motor’s condition over time.
Proper trend analysis helps diagnose a wide range of power-quality-based issues, including:
- Transient voltage or electrical energy surges caused by a sudden release of energy
- Harmonic distortion caused by undesirable additional sources of high-frequency current or AC voltage supplying energy to the motor windings
- Voltage and current imbalances that arise due to differences between the phase angle or voltage magnitudes
Identifying the early signs of motor issues and nipping them in the bud is key to keeping motor failures at bay. By following the steps above, facilities can better catch potential issues before they develop into bigger problems and avoid the cost of asset replacement or downtime. Once your machinery eventually succumbs to the test of time, engaging a mechanical engineering and servicing provider is your best bet at revitalising your assets and sourcing the products they need, such as motor grease or natural ester transformer oil.