How unique is it? Motors that sit on resilient rubber wings typically use which type of mounting? Winding insulation breakdown and bearing wear are the two most common causes of motor failure, but those conditions arise for many different reasons. B) Call the equipment supplier and provide the system model numbers. It is critical to determine the best course of action should a failure occur. 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. When working on a type of system that you have never seen before, you should: A) Locate the manufacturer's troubleshooting guide. Are the techs CSA-certified? Winding contamination cannot always be readily identified as the root cause of an insulation failure. Impact: Mysterious circuit trip due to protective earth current flow, Instrument to measure and diagnose: Fluke 190-204 ScopeMeter Test Tool. 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. Instrument to measure and diagnose: Fluke 810 Vibration Tester. These winding failures fall into four major categories related to what causes them: thermal stress, mechanical stress, electrical stress, and environmental stress. Describe how energy changes as a ball is thrown in the air. A) Adding refrigerant increases the system subcooling. Youll notice there are no solutions or implementation sections. VIEW THE LISTLEARN MORE ABOUT THE PROGRAM, REGISTRATION OPTIONS & PRICINGSCHEDULE OF EVENTS. A quality laser alignment tool can typically determine whether there is a soft foot problem on a rotating machine. Excessive motor heat is a major cause of motor failure. An open winding falls into which general motor failure area? Chances are, you arent the final decision maker on larger operational and capital expenditures. We get it. 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. Pipe strain refers to the condition in which new stresses, strains, and forces, acting on the rest of the equipment and infrastructure transfer backward onto the motor and drive to induce a misalignment condition. 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. Always ensure the motor thermal protector has not opened. In addition, misalignment may feed vibration into both the load and the motor drive shaft. Potential relays measure the back ______ developed across the _______ winding to operate the relay. 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 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. Re-state what you felt caused the failure. |, free online repair or replace decision-making tool. Rotating looseness is caused by excessive clearance between rotating and stationary elements of the machine, such as in a bearing. For decades, plant personnel have performed insulation resistance tests with handheld megohmmeters to prevent motor failures that lead to costly unplanned shutdowns, failure-to-produce penalties and rewinding repairs. When a split AC system using a capillary tube is overcharged: Three general areas of problems in air-conditioning systems include electrical problems, mechanical problems, and: The evaporator coil operating temperature for a system with a 20F split, 85F return air, and 71F supply air is: A high temperature differential (more than 2 degrees) between return air temperature at the grille and the return air temperature at the unit indicates: When an air-cooled split system operates at low ambient temperatures: C) Low ambient controls are necessary for safe operation. | Site Design & Development by Human_Code. D) The large temperature drop indicates the airflow is less than required. The stator produces electromagnetic energy, either through windings or permanent magnets. When you suspect an issue with your electric motor winding, there are three categories of measurements to help identify the likely source of failureselectrical, mechanical, and thermal. Organize the content under subheadings that make sense. But a bearing failure will always be the result of another issue, either in the motor or the plant, such as vibration, high ambient temperature, moisture, misalignment, shaft voltage and motor overload. 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. And fifth, use your motor shop to help you implement best practices for motor replacement, repair, storage and maintenance at your plant. Fault isolation diagrams and troubleshooting tables help the technician locate problems through the process of: The refrigerant condensing temperature for an air-cooled system having a 20F split is: The most common airflow problem experienced on air-conditioning systems is: C) Low airflow caused by dirty or plugged air filters. To help mitigate these failures, a variety of motor tests can be performed on electric motors. Switching power circuit, capacitor discharges, or solid-state power devices can also cause this type of motor winding damage Prescriptive maintenance is the next big step forward in the evolution of asset management, Read More Moving toward smart maintenance with prescriptive analyticsContinue, Read More As solar production rises, remote monitoring can improve efficiencyContinue, Dave OReilly, VP of Commercial, Fluke Corporation, offers a sneak peek of our upcoming webinar, Read More Why you should integrate your dataContinue. Contamination from dust, dirt and chemicals is one of the leading causes of motor failure. Acid test kits and sight glasses help to identify a system contaminated by moisture and acid. There are several actions that could trigger this block including submitting a certain word or phrase, a SQL command or malformed data. Maintenance software and data gathering devices that integrate with third-party solution providers are ideal to accomplish this. The first signs of this problem will be noise and overheating as the bearings begin to lose their original shape and metal fragments mix with the grease and increase bearing friction. Insulation failures are typically caused by contaminants, abrasion, vibration, or voltage surge. And so on. Some plants prefer to perform their own motor repairs. The sigma currents are created as a result of the signal frequency, voltage level, capacitance and inductance in conductors. If the failure was catastrophic, repair may not be a good idea. Unequal voltages usually are caused by unbalanced loads on the power source, a poor connection at the motor terminal, or a high resistance contact (weak spring). Insulation failures are typically caused by contaminants, abrasion, vibration, or voltage surge. 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. Common air conditioning controls are switches that open or close based on a monitored condition such as: After determining that a high pressure switch is open, the next step is to: A high resistance problem can be detected by. Insulation issues can be the result of unequal voltage between phases due to unbalanced loads on the power source, a poor connection at the motor terminal, or high resistance contact. a) tight enough so that it does not slip on startup Yet determining the cause is a critical step in protecting your motors. You can email the site owner to let them know you were blocked. Whilevibration analysiscan be used to test critical motors for imbalance, misalignment, mechanical looseness, a bent shaft, critical speeds and more, its particularly helpful with identifying bearing problems. Motor starting components can be made up of: Internal centrifugal switches, relays, starting, and running capacitors. What term expresses the ability of the motor to work beyond its rated output? 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. Do you need OEM parts or can your motor shop fabricate or source OEM-enhanced parts? This offline testing, often called static testing, looks at insulation resistance, wire damage and current leakage. Next up is advice on troubleshooting, fault testing, motor failure reporting and decision-making, including when to call in a motor shop. Many professionals believe that a flexible coupling eliminates and compensates for misalignment, but a flexible coupling only protects the coupling from misalignment. Energized testing takes place while the equipment is under a simulated load to reveal problems that occur during operation. It raises the clavicle. Sounds simple. Some motor shops offer their customers a24/7 online motor management systemto help them keep track of their assets, including maintenance and repair histories. Reactive and preventive maintenance will always have a part in your operations. 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. A) Fan RPM = Motor RPM Motor Sheave Diameter Fan Sheave Diameter. Using your existing staff, and scaling as necessary, you can implement without costly retrofitting and large IT infrastructure investments. This condition can create a frustrating situation in which tightening the mounting bolts on the feet introduces new strains and misalignment. Look for a shop that does best practice mechanical and electrical conformance testing, including vibration spectrum analysis, dynamic balancing, surge testing and core loss testing. Imbalance is a condition of a rotating part where the center of mass does not lie on the axis of rotation. This imbalance can lead to stresses in each of the phase circuits in a three-phase power system. a. Include data and observations. This weakness is . 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 . b) insulation faults 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. They can test correct shaft alignment, imbalances, looseness, misalignment, and bearings. Charred connections in the motor's connection (terminal) box are a sure indication of this problem. 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. Look for a clear, comprehensive, standardized reporting process, including rigorous visual and written documentation. Other failures are caused by vibration, physical damage and situations that causes excessive heat. Failuresare shown here to help identify the causes of failure, so that, where possible, preventative measures may be taken. This article demonstrates how to detect the 13 most common causes of winding insulation and bearing failure in advance. Sigma current can be found in the motor cabling and is the sum of the current of the three phases at any one point in time. Unfavorable operating conditionswhether electrical, mechanical, or environmentalcan dramatically shorten the life of an electric motor. In other words, there is a heavy spot somewhere on the rotor. Gives a bottom-line summary of the essential information in the report in approximately 100 words. Because 30% of motor failures are caused by overloading, it is important to understand how to measure for and identify motor overloading. These transients, which vary in amplitude and frequency, can erode or cause insulation breakdown in motor windings. De-energized testing runs a motor through its paces while its turned off. However, these tests only provide a "snapshot" of motor health. Weve spent most of this guide talking about what to do when a motor fails. One of the most common causes of electric motor failure is bearing issues, responsible for around 51 per cent of failures. We wrap it up by looking at the bigger picture, including how to perform a root cause failure analysis and prevent motor failures in the future. 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. The failure mechanism involves the gradual development of a weakness in the insulation. There could also be thermal deterioration in all phases of the stator winding typically due to load demands exceeding the rating of the motor or by very high currents in the stator winding due to a locked rotor. To start investigating harmonic distortion, use a power quality analyzer to monitor electrical current levels and temperatures at transformers to be sure that they are not overstressed. Explain your reasoning. What causes the little pops and ticking that can be heard in some furnaces before the blower comes on? Note:A one-percent voltage unbalance may result in a six- to ten-percent current unbalance. Impact: Arcing across bearing surfaces create pitting and fluting resulting in excessive vibration and eventual bearing failure. The benefits of these maintenance software tools include: Leveraging these tools and technologies can offer key insights into the health of electric motors. Winding shorted phase-to-phase This type of insulation failure is typically caused by contaminants, abrasion, vibration or voltage surg 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. Yes, itll require some upfront work. A common cause of an open winding is undersized lead lugs. 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. An open internal motor overload is distinguished by: Motors that sit on resilient rubber rings typically use which type of mounting? C) Unusual airflow restrictions in the duct. Various factors, such as overheating, physical damage . Our tools can also check the drives output and power distribution, uncovering energy losses and improving efficiency. These next-generation maintenance and reliability tools support the generation, collection, and consolidation of data from sensors, tools, and existing systems. The open is usually caused by a blown fuse, an open contactor, a broken power line or bad connections. e) all of these, When measuring the leads of a multispeed shaded pole motor, there should be measurable resistance between all the leads. What is the most likely cause of flames that are lifting off the burner? But, while predictive maintenance techniques, such as vibration analysis, are often used to . Offer key insights into the health of electric motor failure area a open motor winding failures can be identified by foot on... Model numbers shop fabricate or source OEM-enhanced parts result of the leading causes of electric motor condition a. Quot ; of motor tests can be made up of: Internal centrifugal switches relays!, a variety of motor failure, so that, where possible, preventative measures be! 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