But the down-the-road benefits will pay off big. [12], 2012 b) Reverse Phase sequence fault In three phases when two phases of supply line reverses. near the wall? 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. Winding shorted turn-to-turn Imbalance is a condition of a rotating part where the center of mass does not lie on the axis of rotation. Simply saying the cause of a motor failure was bearing failure may be true. Open windings are also caused by shorted turns, phase-to-phase shorts, ground-to-frame shorts, faulty internal coil-to-coil connections, severe overloads, and physically damaged coils. Located between the stator and rotor, bearings are used to keep the rotor centred and shrink the air gap. This article demonstrates how to detect the 13 most common causes of winding insulation and bearing failure in advance. A quality laser alignment tool can typically determine whether there is a soft foot problem on a rotating machine. Why. Winding Shorted Turn-to-Turn Capture and document critical measurements at installation, before and after maintenance and on a routine basis. You can add these sections to your failure report if youre responsible for them at your plant, or you can leave them to the motor shop. These values could be affected by the position of the squirrel cage rotor during testing. Check each wire, including T1, T2, T3 and the ground wire. In other words, there is a heavy spot somewhere on the rotor. This will minimize your work and bring motor expertise and practical assistance to the table. What type of drive would move the driven device at the same speed as the motor? Maintenance software and data gathering devices that integrate with third-party solution providers are ideal to accomplish this. The stator is the stationary part of the motor. Do these five things and youll increase uptime, reliability and productivity at your plant and look like a hero to your boss. An open internal motor overload is distinguished by: The RPM of a belt driven blower can be determined by: Multiplying motor RPM and motor sheave diameter and then divide by the fan sheave diameter, When checking the resistance of a dual voltage wye motor, there should be ______ resistance readings. The benefits of detecting, identifying, and evaluating electric motor abnormalities are decreased motor failures and less unexpected downtime. quent compressor failure can result within a few hours. If youre involved in plant operations or maintenance, no one has to tell you how important industrial motors are to your day-to-day productivity and annual profits. 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. The imagers test faulty connections, overheated bearings, and tank levels. Why doesn't uranium ore spontaneously undergo a chain reaction? 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. Skip to the next section on. Motor starting components can be made up of: Internal centrifugal switches, relays, starting, and running capacitors. Bloch doesnt recommend taking your equipment failure report any further than the failure analysis. Finding the source of these transients can be difficult because of the infrequency of the occurrences and the fact that the symptoms can present themselves in different ways. This will minimize your work and bring motor expertise and practical assistance to the table. How long have the staff been there? 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. (If youve had small children in your life, youll also have flashbacks.) At the simplest level, all three phases of voltage should always have the same magnitude. 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. relay coil in series with the run winding and the contacts wired in series with the start winding, When checking the resistance of a dual voltage delta motor there should be ________ resistance readings. Weve put together a separatepreventive maintenance guideto help you out. Instrument to measure and diagnose: Fluke 810 Vibration Tester. 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. Here are 3 ways to tell if youre doingpreventive vs predictive maintenance. These transients, which vary in amplitude and frequency, can erode or cause insulation breakdown in motor windings. Winding insulation breakdown and bearing wear are the two most common causes of motor failure, but those conditions arise for many different reasons. Know the breakpoints at which youre willing to repair vs. replace. |, free online repair or replace decision-making tool. This will appear as an open circuit condition across the motor winding. Should we repair the motor or replace it? Other tests includeinsulation resistance testing(ensuring the insulation resistance of the motor decreases after it starts),DC step voltage testing(plotting the current that results from increasing the voltage applied to the insulation to look for a non-linear graph),HiPot testing(looking for leakage current as a way of establishing the effectiveness of insulation). Winding Failures. Published: January 2021 In response to various opinions about the feasibility of maintaining motor efficiency during repair, including replacement of the stator winding, the Electrical Apparatus Service Association (EASA) and the Association of Electrical and Mechanical Trades (AEMT) conducted two comprehensive rewind studies . The failure mechanism involves the gradual development of a weakness in the insulation. In this case, different is better. The Effect of Repair/Rewinding on Premium Efficiency/IE3 Motors. Data integration and mobility tools integrate third-party systems to connect facility maintenance departments to operational metrics. If the failure was catastrophic, repair may not be a good idea. Sigma currents are essentially stray currents that circulate in a system. There are several actions that could trigger this block including submitting a certain word or phrase, a SQL command or malformed data. The open is usually caused by a blown fuse, an open contactor, a broken power line or bad connections. 1 in 10 failures are mysterious. Nearly half (48 percent) of all motor failures are due to electrical issues, according to a survey by the Electric Power Research Institute (EPRI). The root cause methodology starts with the failed component, then follows a step-by-step process to understand the stresses that caused the component to fail. The machines provide the data. To diagnose a problem, there are three steps within each category to help quickly and efficiently manage the repair workflow: Before returning the machine to service, perform a quick screening to ensure the repairs are completed. Motors are used everywhere in industrial environments and they are becoming increasingly complex and technical, sometimes making it a challenge to keep them running at peak performance. Weve come up with these. This problem typically occurs when the insulation in the windings deteriorates. D) Suction pressure goes down and superheat increases. Including a winding that is shorted phase-to-phase or turn-to-turn, has a shorted coil, is grounded at the edge of the slot or in the slot, or has a shorted connection. On PSC multi-speed indoor blowers the wire that is wired to power regardless of speed is the ________ wire. Identify causes you eliminated and why. Hopscotching is an electrical troubleshooting technique that works by: A) Starting at a point where voltage exists and moving one lead at a time from point to point toward the non-functioning load until voltage is lost. To get there, you have to understand the underlying causes of motor failures. Note:A one-percent voltage unbalance may result in a six- to ten-percent current unbalance. To get a complete picture, evaluate the likely failure modes and match the right maintenance technologies with the most likely failure mode. When the winding is energized, it forms magnetic poles. Sigma current can also be understood as asymmetrical signals in multiple conductors that can capacitively couple currents into the ground conductor. An open winding will display several different symptoms, depending on the motor's internal connection. We've put together a post onwinding failure, with awesome photos courtesy of EASA, if you're looking for examples. You need to consider the cost to replace, cost to repair, cost of down-time (including domino effects on the plant and company as a whole) and long-term costs, such as repairing an old motor thats an energy hog. Document operating condition, machine specifications and performance tolerance ranges. Starts (too many, not enough of a break between them or extended start times) are the culprit in some rotor failures. A) motors, When hopscotch troubleshooting, follow the schematic and move the meter lead on the control side of the circuit from one control to the next, checking the voltage in and out of the control. 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. It treats the underlying condition that created the situation in the first place. b) insulation faults Iron(III) sulfate $\left[\mathrm{Fe}_{2}\left(\mathrm{SO}_{4}\right)_{3}\right]$ is composed of $\mathrm{Fe}^{3+}$ and $\mathrm{SO}_{4}^{2-}$ ions. You remove the end bell, and the entire winding can be examined. It can also be a process that takes several months and proceeds systematically through all six steps, perhaps with external support from a consultant or experienced motor shop. Various factors, such as overheating, physical damage . C) Unusual airflow restrictions in the duct. The benefits of these maintenance software tools include: Leveraging these tools and technologies can offer key insights into the health of electric motors. 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. Soft foot is often manifested between two diagonally positioned mounting bolts, like the way that an uneven chair or table tends to rock in a diagonal direction. Shaft failure is the least common cause of motor failure. For this reason, it is important to check machine alignment more than just at the time of installationprecision alignment is a temporary condition that can change over time. Polarization index (PI) testing takes a ratio of the winding insulation resistance after 1 minute and 10 minutes to tell you how well the motor is functioning. Start reaping the benefits of membership today. The open is usually caused by a blown fuse, an open contactor, a broken power line or bad connections. Most insulation failures ultimately lead to a ground fault, often with a considerable damage to the surrounding parts of the motor. 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. 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. Leveraging these tools offers facilities the greatest flexibility and power to manage the health of electric motor windings. 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! After all, simply knowing that a bearing failed or the winding insulation is a charred mess wont stop it from happening again. A megohmmeter can detect: Thermal Stress Failures. Here are some of the more common motor tests to perform regularly as part of your early warning system. Create an archive reference of measurements to facilitate trend analysis and identify change of state conditions. This report may come from your motor shop. Insulation failures are typically caused by contaminants, abrasion, vibration, or voltage surge. Are you interested in learning more about how to determine the true cause of an electric motor failure? Fluke Reliability helps you find the best solutions for your electric motor problems. Variable frequency drives employ a pulse width modulation (PWM) technique to control the output voltage and frequency to a motor. Bearing failure is an expensive problem both in terms of motor repair and downtime, so helping to prevent this by measuring shaft voltage and bearing current is an important diagnostic step. What you get:We start with a fast review of the parts of an AC and DC electric motor so were all speaking the same language. Often these mechanical faults are related: shaft imbalance, looseness, or misalignment left uncorrected will cause increased forces on the bearings which leads to rapid wear of the bearings. With single phase motors, the polarity of the shaded pole or start winding determines the motor rotation. Determine a balanced chemical equation for the formation of barium chloride. Grounded windings can be detected by measuring the resistance with a multimeter between: What type of drive would move the driven device at the same speed as the motor? Bearings - 51% Windings - 16% External causes -16% Unknown - 10% Rotor - 5% Shaft or coupling - 2% Repair or replace? Imbalance can be caused by numerous factors, including: A vibration tester or analyzer can help you determine whether a rotating machine is in balance. The best way to diagnose an ECM motor is to: D) Turn off power to the unit, remove the control harness, and connect a test controller, Larger blower wheels are typically operated by ________ motors. Weve spent most of this guide talking about what to do when a motor fails. Explain why a sample of iron(III) sulfate is uncharged. You can identify dead shorts, loose connections and open circuits in coiled windings using a digital multimeter. 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. Angular soft footangular soft foot occurs when one of the mounting feet is not parallel or normal to the mounting surface. An imbalance in impedance or load distribution can contribute to imbalance across all three of the phases. Transient voltages can come from several sources either inside or outside of the plant. However, whether or not you can see the defective winding, an oil sample should always be taken for evaluation. There are four key strategies that you can undertake to restore or prevent premature failures in motor drive and rotating component: https://help.fluke.com/hc/en-us/requests/new, Fluke virtual demos and product selectors, Fluke 438-II Power Quality and Motor Analyzer, Fluke 289 True-RMS Industrial Logging Multimeter, How to use criticality analysis to prioritize assets, Electric motor efficiency and reliability: New testing approach matches real world conditions, See how the 438-II Motor Analyzer is building an underwater fan club, 3 ways to improve motor health with vibration testing, Five key test points for understanding motor drive efficiency and performance, Fluke 1587 Insulation Multimeter helps keep 1950s motors and generators running into the 21st century, A motor braking manufacturing plant steps up to proactive maintenance, Angular misalignment: shaft centerlines intersect but are not parallel, Parallel misalignment: shaft centerlines are parallel but not concentric, Compound misalignment: a combination of parallel and angular misalignment. 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. a) tight enough so that it does not slip on startup Butdont screw it up. We also frequently offer a companion 2-day Root Cause Failure Analysis seminar which includes this book as well as a CD-ROM containing a color version of the book. The resistance of ________ can accurately be predicted using Ohm's law. Charred connections in the motor's connection (terminal) box are a sure indication of this problem. D) The large temperature drop indicates the airflow is less than required. (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.). Misalignment occurs when the motor drive shaft is not in correct alignment with the load, or the component that couples the motor to the load is misaligned. PM has been shown to reduce downtime by as much as 50%. However, electric motors can be prone to any number of issues that lead to motor faults and failures. 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); What is the effect on suction pressure and superheat? Then we identify the 5 common causes of industrial motor failure. The motor and insulation tester assure safe operation, prolongs the life of electrical systems and motors. Well help you select the right product for your needs. In a perfect situation, the sum of the three currents would equal zero. Impact: Accelerated wear on rotating components resulting in bearing failure. Are the techs CSA-certified? It is critical to determine the best course of action should a failure occur. takes place while the equipment is under a simulated load to reveal problems that occur during operation. Potential faults may be in the cabling to the motor, the terminations at the motor, and potentially the windings themselves. This website is using a security service to protect itself from online attacks. For this reason, it makes sense to begin your troubleshooting by checking for motor overload. A tri-fold brochure containing the information on this page is available for purchase. Its one thing to identify the component thats failed and another thing to isolate the cause of that component failure. Impact: Premature wear on motor electrical and mechanical components leading to permanent failure, Instrument to measure and diagnose: Fluke Ti480 PRO Infrared Camera, Fluke 289 True-RMS Industrial Logging Multimeter. 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