Taking care of your electric motor can provide you with a long service life reducing downtime and lost productivity. Proper care involves a good preventative maintenance schedule that includes keeping detailed records that enable operators and engineers to spot patterns and predict problems before they occur. By proactively maintaining your equipment, many problems can be avoided and quickly dealt with during scheduled downtime to keep lost productivity to a minimum.
Here are 5 common issues that you can proactively identify to improve your motor performance and extend its lifespan.
Vibration is one of the most common ways to shorten your motors’ overall life. It can damage other parts of the motor and cause loose electrical connections. Vibration is especially harmful for bearings; reducing the ability of the bearing lubrication to reduce friction. Even very small amounts of vibration can dramatically reduce the service life of the bearing.
On medium to larger machines, it is a good idea to set up a testing schedule. This could be done every 3-6 months depending on the equipment and how valuable downtime is to you. If you have lots of motors in this range, it might be a good idea to purchase a mobile field vibration analysis tool.
Causes of Vibrations
- Damaged bearings
- Unbalanced and poorly aligned loads
- Poor-quality power supply
- Check the condition of the bearings and have the motor overhauled if necessary
- Ensure that the motor and load are securely mounted and properly aligned
- Check that the voltage and current are within nameplate specs and that the phases are balanced
- Check and tighten electrical connections that may have come loose from vibration.
Overheating an electric motor is one of the fastest ways to reduce the motor’s service life and is especially harmful for the winding insulation and bearing lubrication.
Causes of Overheating
- Running your motor at lower speeds can also cause heating issues. In Totally Enclosed Fan Cooled (TEFC) and Open Drip Proof (ODP) motors, the cooling system consists of a shaft-mounted fan. A reduction in speed results in reduced airflow over the motor and loss of cooling, causing heat build-up. A motor is usually designed to operate at a base speed set by the manufacturer. Motors that operate below the base speed may experience reduced efficiency in the cooling system. When the motor is operating at full torque at low speed, heat can quickly build up inside the motor. Refer to the manual on the limitations of the motor if you intend on running the motor at slower than designed speeds.
- Bearing lubrication breaks down under excessive heat, and it may be necessary to replace the lubrication in unsealed bearings, or replace sealed bearings, if the lubrication is no longer able to do its job to keep the bearing cool and reduce friction during motor operation.
- As a preventive measure, you may need to conduct infrared thermography test. This can capture the infrared energy of motor components without interfering with motor operation. This allows you to pinpoint sources of potential problems before they cause damage, whether it’s a winding or mechanical issue.
- Keep your motor running within the recommended service levels. Review the product manuals for specific scenarios. These documents give you guidelines on how long the motor can operate under standard, severe, or extreme levels of service.
- If the motor is stopped and started frequently under load, make sure that it is fitted with a soft starter or a speed controller such as a VFD (Variable Frequency Drive), enabling it to accelerate smoothly without drawing excess current that builds up heat inside the motor.
Depending on the environment the motor operates in, it is susceptible to dirt, particle debris, and/or moisture. These contaminates can interfere with the cooling of a motor and damage its bearings.
Some motors are specifically designed to operate in more severe environments. Their enclosures are able to handle the hazards the environment presents. For example, a total enclosed stainless steel motor is specifically designed to keep the moisture and grime out in highly contaminated environments.
Ensure that the environment around the motor is clean, and that the ventilation ports and fans are free of grime and dirt build-up.
- Use a brush or a moderate level of compressed air to clean the outside of the motor including the cooling fins on a regular basis.
- Check contacts, brushes, relays and any other electrical connections to make sure they are not being interfered with by dirt and other contaminants and are free of corrosion.
- Keep motors free of moisture during operation and in storage. Moisture can lead to corrosion that damages the motor windings, bearings and electrical connections. Motors that are infrequently operated are at particular risk of moisture build-up, as the motor ventilation system is not keeping the moisture out when they are not operating.
- Take extra care with any parts of the motor when putting them in storage, and be sure they are cleaned before putting them back in service.
Ensure the motor bearings are always properly lubricated according to manufacturer’s specifications, and sealed bearings must be replaced when they reach the end of their service life. When lubricating bearings, do not overfill them, as the excess can be ejected inside the motor during operation, contaminating the windings and interfering with electrical connections.
#5 Current and Voltage
For maximum service life, the voltage and current of the motor must be maintained within the correct specifications. Under-voltage causes the motor to run poorly and can create heat damage in the motor windings. Current spikes, which can occur during fast acceleration under load, or sudden changes in the load, are a prime source of heat damage inside a motor. If your motor uses a strong current but suffers from current spikes, consider using a soft starter or a speed controller such as a VFD (Variable Frequency Drive). These controls will safely control the current running to your motor, enabling it to accelerate smoothly without drawing excess current that builds up heat inside the motor.
Detection and Prevention
Ensure that the motor has a strong connection to the power supply. Voltage dips and spikes can occur if there is a poor connection. If voltage spikes are found, a line reactor may be required to smooth it out. If the voltage at the motor is consistently lower than the voltage at the power supply source, check for long cable runs, loose or bad connections that may be causing a voltage drop. Poor connections can be detected by measuring the resistance across the connection when not in operation, or the voltage drop while the motor is running. If you are running a 3-phase motor, make sure all the connections have equal voltages and currents.
Purchasing a high-quality electric motor, and taking care of it with regular preventative maintenance, ensures a long and trouble-free service life with uninterrupted productivity. eMotors Direct offers a range of high-quality, tough and reliable electric motors and drives for every type of application in every type of environment. Get in touch with us today to find out what our products can do for you!
Credit: William von Schrottky