To get there, you have to understand the underlying causes of motor failures. Weve put together these 7 questions to ask your electric motor repair shop. Motors are rated in either ________ or ________ operation. Connected tools and sensors offer all key stakeholders with access to the data they need. Create an archive reference of measurements to facilitate trend analysis and identify change of state conditions. 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. This type of insulation failure is typically caused by contaminants, abrasion, vibration or voltage surge. Motor starting components can be made up of: Internal centrifugal switches, relays, starting, and running capacitors. 4. It can also detect the presence of dirt or moisture. Indicate the relative amounts of potential and kinetic energy at each position. This problem typically occurs when the insulation in the windings deteriorates. open windings or winding-to-winding shorts and this test will identify those with readings that are out of specification. Does the shop have a significant amount of experience with your motor? The machines provide the data. Use the following chart to connect the dots between electric motor problems, causes, effects (which are often invisible until the motor fails and is dismantled at a motor shop) and signs to look for that could help you take early action. De-energized testing runs a motor through its paces while its turned off. Physical damage, corrosion, improper installation and excessive loads are often the root cause. Bearing failure can be caused by several things: A heavier load than designed for Inadequate or incorrect lubrication Ineffective bearing sealing Shaft misalignment Incorrect fit Normal wear Induced shaft voltages All photographs are copyrighted 1985-2019byEASA. 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. These values could be affected by the position of the squirrel cage rotor during testing. What type of drive would move the driven device at the same speed as the motor? Excessive motor heat is a major cause of motor failure. An open winding falls into which general motor failure area? Whats the shops inventory of parts and materials for repairs? a) will draw higher than normal amps A tri-fold brochure containing the information on this page is available for purchase. 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. A single-phased winding failure is the result of an open in one phase of the power supply to the motor. Failures disrupt business operations, decrease productivity, and adversely impact a companys bottom line. 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. a) contamination Yet determining the cause is a critical step in protecting your motors. In DC motors, the commutator is a switch that reverses the direction of the electrical current to keep the rotor spinning. EASA's Root Cause Failure Analysis manual covers root cause methodology and the specfic stresses that affect each component of an electric motor. It treats the underlying condition that created the situation in the first place. The most common mechanical faults are shaft imbalance, looseness, misalignment, and bearings. Insulation failures are typically caused by contaminants, abrasion, vibration, or voltage surge. Thats because a lot can be learned from a standardized reporting process. What causes the little pops and ticking that can be heard in some furnaces before the blower comes on? Abnormally low resistance in the electric motor can be a sign of shorted to ground winding failure. This website is using a security service to protect itself from online attacks. Failuresare shown here to help identify the causes of failure, so that, where possible, preventative measures may be taken. If its an older motor, can you find a new motor that will fit in the old spot, given that new motors tend to be smaller than an equivalent motor made 25-plus years ago? Instrument to measure and diagnose: Fluke 810 Vibration Tester. Do they follow the ANSI/EASA AR100 best practices? It may also occur as a result of excessive starts or reversals. Heres how a motor failure report can help with motor management. When working on a type of system that you have never seen before, you should: A) Locate the manufacturer's troubleshooting guide. What is the effect on suction pressure and superheat? Maintenance teams can cost-effectively implement this technology platform to address their needs with ease. 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. 195.201.81.185 Starts (too many, not enough of a break between them or extended start times) are the culprit in some rotor failures. In addition, misalignment may feed vibration into both the load and the motor drive shaft. Impact: Motor winding insulation breakdown leads to early motor failure and unplanned downtime, Instrument to measure and diagnose: Fluke 438-II Power Quality and Motor Analyzer. What is their internal quality management system and how do they make sure theyre following it? Butdont screw it up. Re-state what you felt caused the failure. 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. Non-rotating looseness happens between two normally stationary parts, such as a foot and a foundation, or a bearing housing and a machine. Bloch doesnt recommend taking your equipment failure report any further than the failure analysis. This can lead to bearing destruction within a few months of motor operation. Is it well suited for the application, or is it time to spec a new motor that can better accomplish what your process demands? Smith, Michael Abbott. This article demonstrates how to detect the 13 most common causes of winding insulation and bearing failure in advance. Thats why its so important to get to the root cause of a failure. Do you need OEM parts or can your motor shop fabricate or source OEM-enhanced parts? Keep all of your organizations assets up and running without downtime. 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. Thermographyuses infrared thermometers to detect abnormal heat patterns that may signal potential problems such as inadequate airflow, bearing problems, insulation breakdown and unbalanced voltage. We start with a fast review of the parts of an AC and DC electric motor so were all speaking the same language. How unique is it? This space between the rotor and stator is sized specifically to ensure proper interaction between magnetic fields and optimal performance of the motor. Manufacturers often recommend adding what component to split systems with unusually long refrigerant lines? If not, you might not get the most qualified team or best price. Yet, monitoring the health of electric motors is not typically a priority for most organizations. , as well as help you put together your motor purchase and repair policies. 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. If there is no resistance or the resistance is uneven, the motor is likely faulty. Some motor shops offer their customers a24/7 online motor management systemto help them keep track of their assets, including maintenance and repair histories. It may also occur as a result of excessive starts or reversals. 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. Extent of failure. However, electric motors can be prone to any number of issues that lead to motor faults and failures. Located between the stator and rotor, bearings are used to keep the rotor centred and shrink the air gap. 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. EASA-validated. Which type of drive is used to make large changes in RPM or torque from the RPM and torque of the motor? 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. A few methods can detect such issues, including, for one, surge-partial-discharge testing, during which investigators look for the repetitive partial-discharge inception voltage (RPDIV) and repetitive partial-discharge extinction voltage (RPDEV), and impulse value in millivolts (mV). However, these tests only provide a "snapshot" of motor health. Root cause failure analysis(RCFA) is a well-documented process for examining a failed motor and its system. 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. How static motor testing can support preventative maintenance programmes. 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. And fifth, use your motor shop to help you implement best practices for motor replacement, repair, storage and maintenance at your plant. If they dont pass the test, keep shopping. Unfavorable operating conditionswhether electrical, mechanical, or environmentalcan dramatically shorten the life of an electric motor. 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. The winding failures illustrated here are typical of what can happen is such circumstances. As part of a regular maintenance program, next-generation diagnostic and maintenance tools that include connected tools, sensors and software offer the best way to monitor an electric motors health. c) 1/64th inch deflection per 1 inch span between drive shaft and driven shaft 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. At the simplest level, all three phases of voltage should always have the same magnitude. Potential relays measure the back ________ developed across the ________ winding to operate the relay. a) tight enough so that it does not slip on startup Impact: Arcing across bearing surfaces create pitting and fluting resulting in excessive vibration and eventual bearing failure. Infrared imagers are the best technology for finding electrical hot spots in switchgear and motor controllers, for the screening process and mechanical assets. Impact: Imbalance creates excessive current flow in one or more phases that then increases operating temperaturesleading to insulation breakdown. A) Setting the thermostat below room temperature. c. It abducts the arm. Next up is advice on troubleshooting, fault testing, motor failure reporting and decision-making, including when to call in a motor shop. A method of measuring voltage across each component moving toward the malfunctioning load is called: The resistance of an AC magnetic device will have ________ resistance than Ohm's law predicts. Insulation failures like this usually are caused by voltage surges. There are several actions that could trigger this block including submitting a certain word or phrase, a SQL command or malformed data. b) the minimum tension required to keep the belt from slipping at its maximum torque 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. That way your chosen solution doesnt just treat the symptom. 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? Thermal deterioration of insulation in one phase of the stator winding can result from unequal voltage between phases. Your IP: Gives a bottom-line summary of the essential information in the report in approximately 100 words. Include data and observations. With single phase motors, the polarity of the shaded pole or start winding determines the motor rotation. Youll notice there are no solutions or implementation sections. Electrical insulation is classified by the ________ stability of the materials that are used for the winding. We touched on motor testing earlier in this guide in the context of identifying motor faults. When troubleshooting split air conditioning systems be sure to check voltage to: Which of these methods used to determine which component in a circuit is not working properly? Should we repair the motor or replace it? Either no one bothered to determine why the failure occurred, so Bonnett and Yung didnt have any data to work with, or the investigation failed to determine a cause. Ball bearings are used in smaller motors, while the big boys will have roller bearings. Click to reveal 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. This is another biggie. Tied with windings for almost 1 in 5 motor failures, external factors include temperature, contamination, poor maintenance, inappropriate mechanical loads and events such as flooding. Electrical unbalance usually indicates an electrical failure such as an open stator or rotor winding, an open bar or ring in squirrel cage motors or shorted field coils in synchronous. If they can't, lubricate them. Winding Failures. Sounds simple. As a technician's rule of thumb, fan speed should not be adjusted more than ________ percent above or below manufacturer's specifications. | Site Design & Development by Human_Code. 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. Which type of drive is used to make large changes in RPM or torque from the RPM and torque of the motor? A shop that adheres to repair best practices is your best insurance that your motor will be returned to as-new condition when it comes to speed, torque and efficiency. 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. Yes, itll require some upfront work. This will appear as an open circuit condition across the motor winding. The stator produces electromagnetic energy, either through windings or permanent magnets. Thankfully, computerized equipment and tools can detect issues at levels and in places that human senses arent able to. Look on the outside of the motor for other potential problems, like holes or smoke points. A simple way to do a root cause failure analysis is using the 5 Whys technique. 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. The action you just performed triggered the security solution. Fox and McDonald's Introduction to Fluid Mechanics, Alan T. McDonald, John C Leylegian, John W Mitchell, Philip J. Pritchard, Rajesh Bhaskaran, Robert W Fox. In other words, the return current from the drive would be equal to the current to the drive. These next-generation maintenance and reliability tools support the generation, collection, and consolidation of data from sensors, tools, and existing systems. 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. 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. Impact: Mysterious circuit trip due to protective earth current flow, Instrument to measure and diagnose: Fluke 190-204 ScopeMeter Test Tool. Motor windings account for about 32% of all AC electric motor repairs. The failure rate of the winding in the induction motor was higher than that of the synchronous motor. 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. The expected temperature drop through a direct expansion evaporator coil: D) Can be determined with a chart supplied by the coil manufacturer. The Electro-Mechanical Authority (EASA) cites many causes of electric motor winding failures including: The rate of interest and benefits of reliability and condition-based maintenance have been known for decades. 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. In this case, different is better. This is another biggie. Heres how to set your motors up for success, not failure. Which NEMA classification can withstand the highest temperature? There a few types of misalignment: Impact: Premature wear in mechanical drive components that leads to premature failures, Instrument to measure and diagnose: Fluke 810 Vibration Tester, Fluke 830 Laser Shaft Alignment Tool. 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. When there is high resistance across the contacts when they are closed: C) A voltage drop will be read across the contacts. Common causes of winding failure include high temperature, too many starts, contamination, too much current, excessive voltage and physical damage. Which component failure could keep the fan from operating during the heating cycle on a traditional standing pilot gas furnace? An imbalance in impedance or load distribution can contribute to imbalance across all three of the phases. An open winding falls into which general motor failure area? 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). 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. Copyright 2016-2021 Duke Electric. The sigma currents are created as a result of the signal frequency, voltage level, capacitance and inductance in conductors. Reflections are generated when there is an impedance mismatch between the source and load. Improper lubrication, inappropriate mechanical loads, heat, contamination and shaft currents are all the usual suspects when it comes to bearing problems. Uneven mass in motor windings and other wear-related factors. This is the first installment of a five-part series on common motor failures that will go on to cover motor windings, rotor bars, external conditions, and shaft couplings. 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