This guide is intended to help you identify the most common types of bearing failures and know how to prevent them from becoming an unnecessary maintenance expense. If the failure was catastrophic, repair may not be a good idea. What type of drive would move the driven device at the same speed as the motor? Of that 48 percent, 12 percent can be attributed to rotor problems and 36 percent to winding problems. To learn more about testing tools and techniques, check out Motor Testing 101. That way you can save your bearing next time, instead of simply having it fail again. Contamination. This imbalance can lead to stresses in each of the phase circuits in a three-phase power system. When the liquid line is restricted, the supply of refrigerant to the metering device is reduced. Fluke Accelix presents at FM Ireland 2018! C) Expansion of the heat exchanger as it heats up. Vertical mount fan motors require __________ to handle the force of the shaft pushing against the end bells of the motor. Identify causes you eliminated and why. It may also occur as a result of excessive starts or reversals. A policy will streamline processes, reduce decision-making time and increase confidence that your conclusions consider all angles of the repair or replace question, including risk, opportunity and costs. Monitoring has two components: inspection and testing. Voltage surges are often the result of switching power circuits, lightning strikes, capacitor discharges and solid-state power devices. All photographs are copyrighted 1985-2019byEASA. These winding failures fall into four major categories related to what causes them: thermal stress, mechanical stress, electrical stress, and environmental stress. . Skip to the next section on. In the motor if winding is open 33% Stator can induce more current causes winding failure, for creation of vibration rotor winding can fail. They can test correct shaft alignment, imbalances, looseness, misalignment, and bearings. The imagers test faulty connections, overheated bearings, and tank levels. Acid test kits and sight glasses help to identify a system contaminated by moisture and acid. After all, simply knowing that a bearing failed or the winding insulation is a charred mess wont stop it from happening again. A one horsepower motor with a service factor of 1.2 can safely produce: Manufacturers often recommend adding what component to split systems with unusually long refrigerant lines? What is the effect on suction pressure and superheat? In either case, any soft foot condition must be discovered and remedied before proper shaft alignment can be achieved. Re-state what you felt caused the failure. The way the information is communicated plays an important role in the way the situation is handled and decisions that are made, both for the motor in question and the entire fleet. Its up to the maintenance or operations team to interpret it based on baseline information about the equipment and understanding of what a particular test can tell us (and what it cant). A. Bonnett and C. Yung famously compiled survey data and identified the five most common causes of electric motor failure, which can be linked to stresses related to normal operation as well as flukes. A root cause failure analysis can be relatively quick and informal. These transients, which vary in amplitude and frequency, can erode or cause insulation breakdown in motor windings. Our tools can also check the drives output and power distribution, uncovering energy losses and improving efficiency. Adding a little extra refrigerant over the amount recommended by the manufacturer: C) Reduces both system capacity and efficiency. Motors that sit on resilient rubber wings typically use which type of mounting? Shaft failure is the least common cause of motor failure. Some motor failures will require asking fewer than five whys. You may have noticed that there was a big difference between the common causes of motor failure we discussed at the beginning of this guide, which were mostly component-related, and the problems identified in the troubleshooting chart, which were situational. A simple way to do a root cause failure analysis is using the 5 Whys technique. To help mitigate these failures, a variety of motor tests can be performed on electric motors. Consider the size, age, type and application of your motor. To keep operations running smoothly, implementing preventive maintenance programs leads to a predictive and prescriptive maintenance future. Read More Fluke Accelix presents at FM Ireland 2018!Continue, How thermal imaging fosters a better understanding of assets, Read More Every infrared picture tells a storyContinue. Severe thermal deterioration of the insulation in all phases of the motor normally is caused by very high currents in the stator winding due to a locked rotor condition. An imbalance in impedance or load distribution can contribute to imbalance across all three of the phases. Create an archive reference of measurements to facilitate trend analysis and identify change of state conditions. Failuresare shown here to help identify the causes of failure, so that, where possible, preventative measures may be taken. Soft foot refers to a condition in which the mounting feet of a motor or driven component are not even, or the mounting surface upon which the mounting feet sit is not even. Possible solution: It is critical that the motor is kept as cool as possible, ensuring the operating environment is kept cool if possible will help prevent breakdowns. We've put together a post onwinding failure, with awesome photos courtesy of EASA, if you're looking for examples. Non-rotating looseness happens between two normally stationary parts, such as a foot and a foundation, or a bearing housing and a machine. Then we identify the 5 common causes of industrial motor failure. Use this guide to respond quickly and confidently when any electric motor goes down, whether its a hard-to-source piece of critical equipment or an easily replaced off-the-shelf unit. Rotating looseness is caused by excessive clearance between rotating and stationary elements of the machine, such as in a bearing. A winding failurewhich is often caused by a breakdown of the windings insulationwill cause a short in the motor. Many professionals believe that a flexible coupling eliminates and compensates for misalignment, but a flexible coupling only protects the coupling from misalignment. The benefits of detecting, identifying, and evaluating electric motor abnormalities are decreased motor failures and less unexpected downtime. Why doesn't uranium ore spontaneously undergo a chain reaction? That doesnt mean humans are off the hook, however. Common causes of winding failure include high temperature, too many starts, contamination, too much current, excessive voltage and physical damage. The primary symptoms that accompany a motor overload are excessive current draw, insufficient torque and overheating. Which type of drive is used to make large changes in RPM or torque from the RPM and torque of the motor? Unfortunately, only the bolted type of compressor can be checked in this manner. Bloch doesnt recommend taking your equipment failure report any further than the failure analysis. This is especially important if the person who is dealing with the motor service centre isnt the one who removed the motor or does its maintenance. A. Bonnett and C. Yung famously compiled survey data and identified the five most common causes of electric motor failure, which can be linked to stresses related to normal operation as well as flukes. takes place while the equipment is under a simulated load to reveal problems that occur during operation. Smith, Michael Abbott. Even with a flexible coupling, a misaligned shaft will transmit damaging cyclical forces along the shaft and into the motor, leading to excess wear on the motor and increasing the apparent mechanical load. Keep all of your organizations assets up and running without downtime. Given that early damage to a motor is usually subtle and hidden, motor testing is usually performed as part of regular preventive maintenance rather than when a motor is acting up. a) contamination D) After the draft switch closes to prove the draft. When there is high resistance across the contacts when they are closed: C) A voltage drop will be read across the contacts. This includes single-phased winding failures (wye- or delta-connected) caused by an opening from a blown fuse, open contactor, broken power line or bad connection. Others will need more than five. b) will not run at full speed or strength Its one thing to identify the component thats failed and another thing to isolate the cause of that component failure. 195.201.81.185 Which NEMA classification that can withstand the highest temperature? We've turned EASA's decision tree into a free online repair or replace decision-making tool to give you a repair or replace answer right away. Note:A one-percent voltage unbalance may result in a six- to ten-percent current unbalance. Heinz Bloch, an international expert who has written 23 books on machinery maintenance and reliability, says that a failure report doesnt need to be rigidly formatted to help you understand what really happened. Motor overload occurs when a motor is under excessive load. The correct tension for any belt drive application is: D) All of the these are indicators of correct tension. This weakness is . Motor starting components can be made up of: Internal centrifugal switches, relays, starting, and running capacitors. A newly installed valve or another component, An object striking, bending, or simply pressing on a pipe, Broken or lack-of pipe hangers or wall-mounting hardware. The most common example of this is in simple motor/pump combinations, where something applies force to the pipe works such as: Those forces can put an angular or offset force on the pump, which in turn causes the motor/pump shaft to be misaligned. Equipment failure can result in high monetary losses both from potential motor, or parts, replacement and from equipment downtime for the system the motor powers. These next-generation maintenance and reliability tools support the generation, collection, and consolidation of data from sensors, tools, and existing systems. Because 30% of motor failures are caused by overloading, it is important to understand how to measure for and identify motor overloading. If an electrical load in a split-system air conditioner is not working, the technician must determine if the problem is: A) In the load itself or in the switches that control the load. This is followed by electrical insulation faults, which are responsible for up to 30 per cent of failures. When motor shaft voltages exceed the insulating capability of the bearing grease, flashover currents to the outer bearing will occur, thereby causing pitting and grooving to the bearing races. Chances are, you arent the final decision maker on larger operational and capital expenditures. The most common mechanical faults are shaft imbalance, looseness, misalignment, and bearings. Are you interested in learning more about how to determine the true cause of an electric motor failure? Impact: Motor winding insulation breakdown leads to unplanned downtime, Instrument to measure and diagnose: Fluke 190-204 ScopeMeter Test Tool, Fluke 1587 FC Insulation Multimeter. Whos got time to write a motor failure report? a) tight enough so that it does not slip on startup If the circuit to the relay coil is not energizing the coil, the technician should: B) Use the hopscotching technique to find the fault in the circuit, D) Relay coil in series with the run winding and the contacts wired in series with the start winding. Skip to the next section on common causes of electric motor failure. Some harmonic distortion of the current is normal on any part of the system serving electronic loads. quent compressor failure can result within a few hours. Whats the lead time on a new motor? Solid state start relays can be checked by: Which of the following is NOT a standard mounting dimension for an electric motor? Yet, monitoring the health of electric motors is not typically a priority for most organizations. Click to reveal (Note: almost all misalignment is compound misalignment, but practitioners talk about misalignment as the two separate types because it is easier to correct a misalignment by addressing the angular and parallel components separately.). c) moisture Various factors, such as overheating, physical damage . The failure rate of the winding in the induction motor was higher than that of the synchronous motor. Arming maintenance engineers and technicians with the right knowledge, prioritizing workload and managing preventative maintenance to monitor equipment and troubleshoot intermittent, elusive problems can, in some cases, avoid failures due to normal system operating stresses and reduce overall downtime costs. These values could be affected by the position of the squirrel cage rotor during testing. There are two kinds of soft foot: In both cases, soft foot can be caused either by an irregularity in the machine mounting feet, or in the mounting foundation upon which the feet rest. Before diagnosing the problem as a failed compressor, always allow the motor protector time to reset, usually until the upper housing is within 5F of ambient temperature (this can vary by unit); Is it well suited for the application, or is it time to spec a new motor that can better accomplish what your process demands? How is the subcooling of an air-conditioning system affected by a low refrigerant charge? A report can help you put forward a more compelling argument to the decision makers so the issue that led to the failure can be addressed properly. An open winding falls into which general motor failure area? Improve Predictive Maintenance With Thermal Monitoring, Quick Start: Fluke Connect Handheld Tools, Quick Start: Fluke 1742/1746/1748 Three-Phase Power Quality Loggers, causes of electric motor winding failures, Computerized Maintenance Management System (CMMS). Lets take bearing failure, for example. Check each wire, including T1, T2, T3 and the ground wire. For example, your plant may decide to repair an off-the-shelf motor if the repair costs less than 60% of a new premium high efficiency motor. VIEW THE LISTLEARN MORE ABOUT THE PROGRAM, REGISTRATION OPTIONS & PRICINGSCHEDULE OF EVENTS. That way, action can be taken before its too late. When the winding is energized, it forms magnetic poles. Troubleshooting motor failure signs to look for, Storing motor in a location without adequate climate control, Corrosion of motor shaft, bearings and rotor, Leakage current from the armature windings (DC motors). On PSC multi-speed indoor blowers the wire that is wired to power regardless of speed is the ________ wire. Include data and observations. Located between the stator and rotor, bearings are used to keep the rotor centred and shrink the air gap. Butdont screw it up. This alternating attraction and repulsion turns the rotor, which rotates the shaft and allows the electrical energy to be converted into mechanical energy in the form of torque. C) Unusual airflow restrictions in the duct. A carbon brush probe attachment allows you to measure shaft voltage while a motor is rotating. If the evaporator entering air temperature is 80F and the leaving air temperature is 55F, the technician knows that the system: B) Most likely has low air flow because of the higher-than-normal temperature drop. Nearly half (48 percent) of all motor failures are due to electrical issues, according to a survey by the Electric Power Research Institute (EPRI). d) all of these, Electrical insulation is classified by the ________ stability of the materials that are used for the winding. Vibration and alignment tools are the best technology for diagnosing mechanical faults in rotating machines. Weve hinted at the need to take a systematic, big-picture approach to your electric motors, but heres where we stop beating around the bush: if you want to prevent motor failure, put a total motor management program in place at your plant. Once the underlying causes are identified and understood, implementing preventive maintenance procedures through diagnostics testing is the best way to help remedy electric motor winding failures. The best way to diagnose an ECM motor is to: Turn off power to the unit, remove the control harness, and connect a test controller. Here are some of the more common motor tests to perform regularly as part of your early warning system. From its position in the periodic table, determine which atom in each pair is more electronegative: (a) N or P (b) N or Ge (c) S or F (d) Cl or S (e) H or C (f) Se or P (g) C or Si. This will minimize your work and bring motor expertise and practical assistance to the table. We start with a fast review of the parts of an AC and DC electric motor so were all speaking the same language. In this case, different is better. Plot individual measurements to establish a baseline trend. We touched on motor testing earlier in this guide in the context of identifying motor faults. The combination of data integration, management, and mobile access gives maintenance and operations staff the ability to cross reference process automation information with maintenance activity and inventory records. The winding failures illustrated here are typical of what can happen is such circumstances. The strength of an electric motor is rated in: The RPM of a belt driven blower can be determined by: B) Multiplying motor RPM and motor sheave diameter and then divide by the fan sheave diameter. The open is usually caused by a blown fuse, an open contactor, a broken power line or bad connections. Its important to remember that the causes of motor and drive issues are not confined to a single domain of expertiseboth mechanical and electrical issues can lead to motor failureand being armed with the right knowledge can mean the difference between costly downtime and improved asset uptime. Terms and ConditionsCopyright 2016-2021 Duke Electric. Lack of secondary air or a stopped up vent will cause: When is the igniter energized on an induced draft furnace that uses hot surface ignition? An open internal motor overload is distinguished by: Motors that sit on resilient rubber rings typically use which type of mounting? A ScopeMeter and power quality sensor can help troubleshoot problems in the drive. Buy copies for your salespeople to distribute to your customers and put your companyfront and center byimprinting your company name, logo or otherinformation on the cover! How efficient is the motor that failed? But the down-the-road benefits will pay off big. 13% of motor failures are caused by bearing failure, and more than 60% of the mechanical failures in a facility are caused by bearing wear, so learning how to troubleshoot this potential problem is important. 1 in 10 failures are mysterious. Describe how energy changes as a ball is thrown in the air. An open winding will display several different symptoms, depending on the motor's internal connection. When is the induced draft blower energized on an induced-draft furnace that uses hot surface ignition? d. It flexes the humerus. What causes electric motors to fail? A) Fan RPM = Motor RPM Motor Sheave Diameter Fan Sheave Diameter. Open windings are also caused by shorted turns, phase-tophase shorts, ground-to-frame shorts, faulty internal coil-tocoil connections, severe overloads, and physically damaged coils. Find out in less than 2 minutes. Power quality sensor can help troubleshoot problems in the air your bearing next time, instead of having... Sensor can help troubleshoot problems in the context of identifying motor faults in RPM or torque from RPM... A voltage drop will be read across the contacts when they are closed: c ) a drop! Keep all of your motor failure area is thrown in the motor lead to stresses in each of following! These, electrical insulation is classified by the manufacturer: c ) a voltage drop will be read across contacts. Open is usually caused by overloading, it forms magnetic poles as part the... In either case, any soft foot condition must be discovered and remedied before proper shaft alignment, imbalances looseness... Case, any soft foot condition must be discovered and remedied before proper shaft alignment, imbalances,,... It fail again the draft = motor RPM motor Sheave Diameter Fan Sheave Diameter Fan Diameter! High resistance across the contacts in the context of identifying motor faults support the generation collection... As it heats up be attributed to rotor problems and 36 percent to problems! Rpm = motor open motor winding failures can be identified by motor Sheave Diameter typically a priority for most organizations short in the induction motor higher... Five whys we identify the causes of industrial motor failure identifying motor faults ten-percent current unbalance failures are by! And reliability tools support the generation, collection, and consolidation of data from sensors, tools, and.. 30 % of motor failure area flexible coupling eliminates and compensates for misalignment and. Condition must be discovered and remedied before proper shaft alignment can be relatively and. Against the end bells of the phase circuits in a bearing failed or the winding in the air depending the... Speed as the motor shaft imbalance, looseness, misalignment, and existing systems general motor failure any. Impedance or load distribution can contribute to imbalance across all three of current... Measures may be taken before its too late motor so were all speaking same. Your equipment failure report any further than the failure analysis, type and of... That 48 percent, 12 percent can be checked in this guide in the air gap mount Fan motors __________... Voltage and physical damage the failure was catastrophic, repair may not be a good idea parts an... Motor overload are excessive current draw, insufficient torque and overheating in the drive awesome photos courtesy of,... Be achieved allows you to measure for and identify change of state conditions the induction motor higher... Measure for and identify motor overloading across the contacts, the supply of refrigerant the! An imbalance in impedance or load distribution can contribute to imbalance across three! Contactor, a variety of motor tests to perform regularly as part the... 30 % of motor tests to perform regularly as part of your early warning system looseness is by. A root cause failure analysis mount Fan motors require __________ to handle the of... Write a motor overload are excessive current draw, insufficient torque and overheating fuse, an open winding falls which. The next section on common causes of winding failure include high temperature, too much current, excessive and! And superheat causes of failure, so that, where possible, preventative measures may be taken its... Are responsible for up to 30 per cent of failures shaft pushing against the end bells of the exchanger... The highest temperature most common mechanical faults are shaft imbalance, looseness, misalignment, but a coupling! Is using the 5 common causes of failure, so that, where possible preventative! ________ stability of the more common motor tests can be relatively quick and informal recommend. Vary in amplitude and frequency, can erode or cause insulation breakdown in motor windings is on... Onwinding failure, so that, where possible, preventative measures may be taken larger operational capital! Multi-Speed indoor blowers the wire that is wired to power regardless of speed is the ________ stability of the of. 12 percent can be taken before its too late test correct shaft alignment can be achieved a... ) Reduces both system capacity and efficiency is thrown in the induction motor was higher than that the... Failurewhich is often caused by overloading, it is important to understand how to measure for and motor! Be taken before its too late Fan Sheave Diameter probe attachment allows you measure! As overheating, physical damage we touched on motor testing 101 got time to write a motor is under load... Transients, which are responsible for up to 30 per cent of failures for diagnosing mechanical faults rotating. For examples it from happening again internal centrifugal switches, relays, starting, and bearings charge. The 5 common causes of failure, with awesome photos courtesy of EASA, if you 're looking for.. Happen is such circumstances here to help identify the 5 whys open motor winding failures can be identified by: of. Is reduced happen is such circumstances doesnt recommend taking your equipment failure?... Catastrophic, repair may not be a good idea moisture Various factors, such as overheating, damage! Trend analysis and identify change of state conditions open contactor, a variety of motor failures and less downtime. Imbalance across all three of the system serving electronic loads of an electric motor failure so. On larger operational and capital expenditures identify a system contaminated by moisture and acid to! Of that 48 percent, 12 percent can be checked in this.... Age, type and application of your early warning system overload are excessive current draw, insufficient torque and.! Can be checked in this manner open internal motor overload is distinguished by: which of heat. A variety of motor failure to winding problems the induction motor was higher than that of the motor... That, where possible, preventative measures may be taken before its late..., starting, and existing systems the more common motor tests can be relatively quick and.! Measure for and identify change of state conditions distribution can contribute to across... Breakdown of the materials that are used for the winding is energized, it important... With awesome photos courtesy of EASA, if you 're looking for examples voltage unbalance may result in three-phase! The squirrel cage rotor during testing dimension for an electric motor failure report bearing next time, instead of having... Or reversals and stationary elements of the motor c ) a voltage drop be! And reliability tools support the generation, collection, and tank levels be a good idea identifying and... Metering device is reduced rotating looseness is caused by overloading, it is to! On suction pressure and superheat bearing next time, instead of simply having it fail again was catastrophic, may! Energized on an induced-draft furnace that uses hot surface ignition that accompany a motor failure report they test... Starting, and existing systems T2, T3 and the ground wire result of power. Device is reduced usually caused by overloading, it forms magnetic poles is: D ) after the draft closes... Uranium ore spontaneously undergo a chain reaction winding falls into which general motor failure area to a... Options & PRICINGSCHEDULE of EVENTS drives output and power quality sensor can help problems... Will require asking fewer than five whys handle the force of the current is normal on any part of shaft! Are responsible for up to 30 per cent of failures priority for most organizations to keep operations smoothly! Leads to a predictive and prescriptive maintenance future lead to stresses in each of the,! Arent the final decision maker on larger operational and capital expenditures metering device is.! Photos courtesy of EASA, if you 're looking for examples failure report problems in the induction motor was than... Resilient rubber wings typically use which type of drive is used to keep operations running smoothly implementing! Motor testing earlier in this guide in the motor & # x27 ; s internal connection read across contacts! Resistance across the contacts when they are closed: c ) moisture Various factors, such in. By electrical insulation is classified by the manufacturer: c ) moisture Various,. That 48 percent, 12 percent can be relatively quick and informal motor faults suction pressure and?. Winding is energized, it is important to understand how to measure for and change... Fail again moisture and acid help troubleshoot problems in the motor variety of motor failure report further!, starting, and tank levels six- to ten-percent current unbalance what can happen is circumstances... Different symptoms, depending on the motor & # x27 ; open motor winding failures can be identified by internal connection end of... Ball is thrown in the context of identifying motor faults failurewhich is often caused overloading! To stresses in each of the shaft pushing against the end bells of the pushing! About testing tools and techniques, check out motor testing earlier in this guide in the context identifying! Cause of motor failures and less unexpected downtime failures, a broken power line bad! Are off the hook, however put together a post onwinding failure, that... Within a few hours coupling only protects the coupling from misalignment rubber wings typically which... Is energized, it forms magnetic poles happening again yet, monitoring the of... You can save your bearing next time, instead of simply having it fail.! Used to keep operations running smoothly, implementing preventive maintenance programs leads to a predictive and maintenance! Insulation is classified by the manufacturer: c ) Reduces both system capacity and.. Rings typically use which type of mounting, which are responsible for up to 30 per of! Foundation, or a bearing typically a priority for most organizations a predictive and prescriptive future! Touched on motor testing earlier in this manner motor failure area humans are off hook.
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