The Importance of Maintenance in Motor Systems

Introduction

Electric motors are powerful electrical machines used in a wide variety of industrial, residential, and commercial systems to power pumps and blowers, fans, compressors, household appliances, machine tools, disk drives, power tools, electric vehicles, propulsion of trains, etc.

Like any other electrical equipment, electric motor systems are not immune to occasional malfunctions, operational issues, and gradual deterioration. For this reason, they require regular maintenance to keep them in good working condition at all times and avoid frequent failures to ensure operational continuity and prolong their service life.

Types of Motor Maintenance

Maintenance of motors systems can be carried out in three different ways, namely:

Preventive Maintenance: This type of motor maintenance aims to prevent operational problems and ensure that the motor system continuously provides efficient and reliable operation.

Predictive Maintenance: This type of maintenance aims at predicting possible failures and malfunctions of the motor system based on certain operating factors and parameters. Once predicted, the maintenance technicians can take the necessary steps to prevent motor failure.

Predictive maintenance also ensures that the right motor maintenance strategy is implemented at the right time. Regular monitoring of the motor’s operating conditions is required to detect and resolve motor problems/faults before they happen.

Reactive/Corrective/Breakdown Maintenance: The goal of corrective maintenance is to repair and/or replace components of the motor system or the entire system whenever a failure occurs.

Let’s look at what each of the three motor maintenance practices entails.

1. Preventive Motor Maintenance

This is a proactive approach toward maintaining motor systems, whereby scheduled maintenance activities are performed regularly to help prevent unexpected motor failures and unplanned downtimes. This motor maintenance entails four primary action elements: inspection, identification, correction, and prevention.

Below are some of the most essential checks carried out during a preventive motor maintenance program.

Visual Inspections: Check the physical condition of the motor system and associated electrical wiring. For motors operating in extreme environments, check for signs of corrosion and remove all deposits of dirt, dust, and oil in the cover of the motor’s fan to maintain good ventilation and facilitate proper cooling of the motor system. Also, examine the motor windings for any hints of overheating, like a burnt odor.

In addition, thoroughly inspect the condition of the motor stator, rotor, drive belts, and mounting; repair and/or replace all worn-out components. Examine the motor wiring and tighten any loose connections. Visually check for the presence of lubricating oil and grease in the motor bearings.

Commutator and Brush Inspection: Visually examine the motor brushes for any signs of abrasive wear and tear. Replace the brushes that are largely (more than half) worn out. Additionally, examine the commutator to ensure that it has no rough spots, such as grooves, dents, or scratches, which are likely to cause brush sparking. Also, inspect the brush holders and commutator clamping ring, and clean them if dirty.

Inspect the Motor Bearings: Check the motor bearings for vibration and noise; you can use accelerometers to measure the bearing vibration and noise levels. Noisy bearings are mainly caused by poor lubrication, abrasive wear and tear of the bearing surfaces, or dirt accumulation on the bearings. In addition, check for signs of bearing overheating, such as discoloration of the bearing balls/rollers, rings, and cages. After the inspections, clean, lubricate, repair, and/or replace the bearings accordingly.

Note: The requirements for maintaining motor bearings may vary depending on the working environment of the motor system. Hence, one should be aware of the different types of bearings used in various motor systems and their specific maintenance requirements.

Test the Motor Windings: You can use a multimeter (or a volt and an ohm-meter) to test your motor’s windings for ground and internal winding faults, including coil-to-coil and turn-to-turn tests. The tests can help identify open or short-circuit anomalies in the windings as well as “short to ground” faults in the motor circuit. Failures in stator windings may necessitate rewinding of the motor. Also, you should measure the insulation resistance level of the motor windings using a Megohmmeter– an ohmmeter with a very high resistance range.

Perform a Motor Vibrations Analysis: Use appropriate equipment to test for vibration levels in the motor system that may be hard to detect manually. This often helps to identify and eliminate the sources of the vibrations before they degrade the motor performance and efficiency or cause extensive damage to the motor system. In most cases, noise and vibrations in electric motor systems are caused by electrical imbalances, loose components, improper alignment, loose or damaged motor bearings/coils, bent motor shafts, a weak/loose mounting base, and too much tension on the motor’s drive belts.

2. Predictive Motor Maintenance

This is a condition-based motor maintenance strategy in which a motor system is inspected and tested periodically using various motor testing instruments, such as infrared thermal imaging and vibration analysis tools, to identify fault sources way before motor failure.  Thus, with predictive maintenance, motor problems can be detected at an early stage and addressed in a timely manner.

The advent of the Industrial Internet of Things (IIoT) has brought about incredible changes to the predictive maintenance of motor systems used in industrial applications. For instance, IIoT connectivity has given rise to software-enabled predictive maintenance programs designed to collect real-time operational data and comprehensively analyze the operating variables and working conditions of industrial motor systems to identify all possible motor problems for timely corrective actions.  

Some of the critical elements of IIoT-based predictive maintenance for motor systems include:

IIoT-connected condition monitoring devices that collect all the necessary data regarding the state of the motor in real-time and send it to appropriate data analysis software platforms.

Smart temperature sensors for collecting data on the temperature changes in the motor system. For example, smart bearing and winding -temperature sensors provide data that indicates changes in the state of the motor’s health, i.e., they help detect when the motor is starting to overheat.

Smart vibration sensors that collect data on the vibration levels of the motor system. The collected data is then used to create trend lines that help predict motor shaft alignment issues, bearing failure, or lack of mounting integrity.

Machine Learning (ML) software that takes all the collected sensor data and sets the baseline regarding the current condition of the motor system in operation. This facilitates the scheduling of motor maintenance based on actual usage, as opposed to general recommendations from the motor manufacturer.

3. Corrective Motor Maintenance

This is the “run it until it breaks” maintenance strategy, whose primary purpose is to repair and/or replace the motor when it fails.  To carry out an effective reactive maintenance scheme, be sure to examine the failed motor and deduce where the failure occurred in the motor system and why it occurred. For instance, a motor system failure can be a result of a faulty/damaged motor component or inadequate maintenance. Usually, effective preventive and predictive maintenance techniques can help prevent motor failure and eliminate the need for corrective maintenance.

Here are some common types of motor failures and their corrective measures:

Motor Fails to Start: In such cases, measure the voltages of the supply line, fuses, relay contacts, and the star or delta motor connections. Also, measure the voltages in the rotor, brush contacts, insulation of the motor windings, and in the circuit of the starting resistors.

Electrical Overload: This is an overcurrent scenario caused by excessive current flow into the motor windings; the windings’ current draw often exceeds the rated current the motor system is designed to carry efficiently and safely. If motor overload occurs, check the load inertia and replace the existing motor system if it’s too small to handle the current load requirements. If the problem is not the size of the motor, examine the winding insulation, bearing and commutator rings, brushes, resistance circuit, and motor windings to repair or replace, or rewind as necessary.

Motor Overheating: Electric motors normally overheat due to overloading, frequent starting and stopping, poor power conditions, and unsuitable operating conditions. If you notice signs of your motor system overheating, check the amount of current draw, clean the ventilation circuits and grilles, and tighten the terminal board connections. Also, if the motor smokes and burns, check the condition of the windings to repair or rewind as needed.

Bearing Failure: There are a handful of causes of bearing failure in motor systems, including incorrect or inadequate lubrication, contamination, excessive loads, improper handling and installation, mechanical stress, etc. If the motor system is running unevenly, with reduced accuracy, or with excessive noise and vibrations, check for faulty or damaged bearings to repair or replace as necessary. 

Importance of Maintenance in Motor Systems

Regular maintenance of any electrical machine is of utmost importance since it warrants its correct operation, prevents various types of faults, and it also prolongs the service life of the machine. In essence, well-planned and properly executed preventive and predictive motor maintenance programs are key to motor systems’ reliable, long-life operation.

Discussed below are some reasons why carrying out routine inspection and maintenance of motor systems is very important.

1. Enhanced Motor Performance

The performance of electric motor systems gradually deteriorates with constant use, and they tend to become less efficient and unreliable over time. However, implementing a comprehensive preventive/predictive maintenance scheme can delay the deterioration process as problems are quickly identified and resolved as they arise. In addition, regular maintenance, cleaning, and lubrication of motor systems enable them to operate more efficiently. Also, routine inspection and testing of a motor system can help identify any issues that might not be physically visible, yet they continue to hamper the system’s performance.

2. Reduced Motor Failure Rates

Suppose a motor system operates continuously without any preventive or predictive maintenance. In that case, it will break down or malfunction at some point, often leading to costly corrective maintenance and equipment downtime.

Regular effective maintenance programs ensure thorough inspections for the motor system. Issues are identified and addressed before failure, and the motor receives proper cleaning, lubrication, repair/replacement of components, tightening of loose connections, and any other necessary maintenance practice. These activities enable the motor system to run efficiently and reliably, with considerably reduced failure rates and unanticipated breakdowns.

3. Reduced Unplanned Downtimes

Predictive and preventive motor maintenance practices are effective strategies used to reduce or eliminate unplanned downtimes for motor systems. They enable users to identify and resolve the root causes of motor faults early enough before failure occurs, thereby minimizing the frequency of unplanned downtimes due to motor breakdowns. In addition, with an effective predictive maintenance scheme, you can identify a deteriorating motor system and schedule for its repair or replacement at a convenient time for your enterprise. Scheduling maintenance activities during lull periods helps minimize unforeseen work or production losses. 

4. Extended Motor Lifespan

A motor system that is not regularly maintained degrades faster because its problems pile up and are only fixed when it breaks down, and in most cases, unaddressed motor problems lead to permanent damage. Also, corrective maintenance procedures can sometimes cause permanent damage to the motor system, abruptly shortening its service life. In contrast, a motor system that receives regular preventive maintenance through routine inspections and necessary repairs or replacement of parts to address any operational or functional problems stays in good shape and will operate longer.

Moreover, using motor testing tools like infrared analysis to carry out predictive motor maintenance helps detect faulty connections and other abnormalities in motor mechanics. The detected defective conditions can then be resolved before they cause irreparable damage to the motor, thereby prolonging the service life of the motor system. In a nutshell, well-planned and properly implemented predictive/preventive motor maintenance schemes will ensure a long and reliable service life of a motor system.

5. Improved Workplace Safety

A malfunctioning motor affects the efficiency and effectiveness of the equipment or system it’s powering and can also bring about workplace safety incidents. For example, an overworked motor system that does not receive regular and proper maintenance can overheat and even explode, injuring nearby workers. But predictive and preventive motor maintenance strategies that comply with specified safety rules and regulations for motor operation do automatically help reduce the possibilities of workplace safety incidents arising from a faulty or malfunctioning motor system.

6. Energy and Cost Savings

When motor systems become worn out or malfunctioning, they draw more current to perform as needed. This problem can be eliminated by properly maintaining the motor system, which results in significant energy savings. Also, motor faults and failures would be more common without proper and regular maintenance, leading to far too many repairs and replacements that can be costly. Besides, unexpected motor breakdowns due to inadequate or improper maintenance often necessitate emergency repairs and replacements. And unplanned repairs requiring spare parts are typically more expensive than scheduled repairs. With preventive and predictive motor maintenance strategies, one can work with a maintenance budget, allocate maintenance costs effectively, and ensure all the required spare parts are purchased in advance, keeping overhead costs low. In addition, proactive motor maintenance practices also lead to reduced motor breakdowns, fewer emergency repairs, and reduced need for motor replacements. This significantly reduces the operational and maintenance costs for motor systems.

This entry was posted on August 20th, 2023 and is filed under Education, Electrical, Technology. Both comments and pings are currently closed.