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. A winding failurewhich is often caused by a breakdown of the windings insulationwill cause a short in the motor. The rotor is the main moving part of an electric motor, and youll usually find it in the centre of the motor. What is the effect on suction pressure and superheat? Already an expert? Insulation failures are typically caused by contaminants, abrasion, vibration, or voltage surge. 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. A) Fan RPM = Motor RPM Motor Sheave Diameter Fan Sheave Diameter. Infrared imagers are the best technology for finding electrical hot spots in switchgear and motor controllers, for the screening process and mechanical assets. Its responsible for 51% of motor failures. Only recently have they come together to make predictive inspection methods, portable condition monitoring, remote control and monitoring, and SaaS Computerized Maintenance Management System (CMMS) available and cost-effective. Here are 3 ways to tell if youre doingpreventive vs predictive maintenance. 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. Its easy to blame motor failure on age, but the reality is that the unstoppable creep of time is responsible for fewer than 20% of motor failures. B) Call the equipment supplier and provide the system model numbers. This additional energy is not used to turn the motor shaft but circulates in the windings and ultimately contributes to internal energy losses. EASA-validated. 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. Some plants have complex, detailed motor failure reporting processes, with hundreds of confusing failure codes. Rotating looseness is caused by excessive clearance between rotating and stationary elements of the machine, such as in a bearing. Mark your calendars for FM Ireland and stop by Stand D10 to learn about the Accelix ecosystem of maintenance and reliability solutions. When charging a capillary tube system that holds 100 oz., the charge must be: B) Within 5 percent, between 95 and 105 oz. And those issues will have another cause. Some plants prefer to perform their own motor repairs. The voltage will be ________ immediately after the control that is opening the circuit. 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. 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. 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. The motor and insulation tester assure safe operation, prolongs the life of electrical systems and motors. How long have the staff been there? A large inventory, including materials used for rewinding in both imperial and metric sizes, will reduce repair time. 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. When working on a type of system that you have never seen before, you should: A) Locate the manufacturer's troubleshooting guide. The machines provide the data. Foreign bodies which find their way inside the motor can dent bearing . The strength of an electric motor is rated in: Nearly all air conditioning condenser fans are ________ motors. For this reason, it makes sense to begin your troubleshooting by checking for motor overload. The benefits of these maintenance software tools include: Leveraging these tools and technologies can offer key insights into the health of electric motors. A failed bearing has increased drag, emits more heat, and has lower efficiency because of a mechanical, lubrication, or wear problem. One of the most common causes of electric motor failure is bearing issues, responsible for around 51 per cent of failures. c) are hard to detect 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. It may also occur as a result of excessive starts or reversals. In other words, the return current from the drive would be equal to the current to the drive. How unique is it? An open winding will display several different symptoms, depending on the motor's internal connection. Does the shop have experience with your motor? quent compressor failure can result within a few hours. 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. 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. A root cause failure analysis can be relatively quick and informal. Instead, rely on the U.S. Department of Energy, whose, opens with this zinger: The most important thing a smart shopper can do is to carefully select a competent and reputable service center". Shaft failure is the least common cause of motor failure. Create an archive reference of measurements to facilitate trend analysis and identify change of state conditions. Which failure could cause nothing to happen when the thermostat is set to heat? 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. [12], 2012 b) Reverse Phase sequence fault In three phases when two phases of supply line reverses. This offline testing, often called static testing, looks at insulation resistance, wire damage and current leakage. Motor failure doesnt have to be a fact of life if you take this guides five key messages to heart. 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. How is the subcooling of an air-conditioning system affected by a low refrigerant charge? Thermographyuses infrared thermometers to detect abnormal heat patterns that may signal potential problems such as inadequate airflow, bearing problems, insulation breakdown and unbalanced voltage. Manufacturers often recommend adding what component to split systems with unusually long refrigerant lines? 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. 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. Look on the outside of the motor for other potential problems, like holes or smoke points. Not so fast. b) the minimum tension required to keep the belt from slipping at its maximum torque Variable frequency drives employ a pulse width modulation (PWM) technique to control the output voltage and frequency to a motor. Get thebearing failure checklist. Stator winding failures are generally attributed to groundwall or turn insulation failures. Energized testing takes place while the equipment is under a simulated load to reveal problems that occur during operation. A) Setting the thermostat below room temperature. Plant owners, operators, and managers can benefit from both integrated data and maintenance management with a single system. 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 . Reflections are generated when there is an impedance mismatch between the source and load. b) will not run at full speed or strength That way, action can be taken before its too late. Note:A one-percent voltage unbalance may result in a six- to ten-percent current unbalance. D) Suction pressure goes down and superheat increases. Capture and document critical measurements at installation, before and after maintenance and on a routine basis. Motor starting components can be made up of: Internal centrifugal switches, relays, starting, and running capacitors An open internal motor overload is distinguished by: a) measurable resistance between run and start b) infinite resistance between start and common c) infinite resistance between run and common d) all of these d) all of these Bloch doesnt recommend taking your equipment failure report any further than the failure analysis. We can see your eyes rolling. Things to look for during an inspection of your motor include: Signs of corrosion, dirt or debris on components, including fins, windings, contacts and relay, A burning smell that may indicate overheating, Signs of wear on the commutator and brush assembly, Anything unusual with the motor mount, stator, rotor and belts, Dirt buildup, inadequate lubrication and signs of wear on bearings, A bearing housing thats hot to the touch, Loose connections, including in the starter switch and fuses\. But if youre honest, how much of your time is spent firefighting instead of focusing on your to-do list? Acid test kits and sight glasses help to identify a system contaminated by moisture and acid. Second, formalize your documentation and reporting so its easy to get all the information about a particular motor to the people that need it. Does the shop have a significant amount of experience with your motor? Thermal deterioration of insulation in one phase of the stator winding. 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. |, free online repair or replace decision-making tool. Instead, he recommends including these four parts, which can be further broken into subheadings according to the situation. Check each wire, including T1, T2, T3 and the ground wire. Monitoring has two components: inspection and testing. These tools can assess electronic harmonics, distortion, and load studies. Third, make your motor repair and replace decisions using an industry-accepted decision tree oronline decision toolto standardize and speed up your process. We've put together a post onwinding failure, with awesome photos courtesy of EASA, if you're looking for examples. Keep all of your organizations assets up and running without downtime. The most common mechanical faults are shaft imbalance, looseness, misalignment, and bearings. Contact us to speak with a specialist. Winding Shorted Turn-to-Turn Contamination. Motor design. Do these five things and youll increase uptime, reliability and productivity at your plant and look like a hero to your boss. Looseness and bearing failures. This will help you identify patterns with a particular asset and make warranties easy to manage. 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. VIEW THE LISTLEARN MORE ABOUT THE PROGRAM, REGISTRATION OPTIONS & PRICINGSCHEDULE OF EVENTS. Chances are, you arent the final decision maker on larger operational and capital expenditures. Should we repair the motor or replace it? The open is usually caused by a blown fuse, an open contactor, a broken power line or bad connections. Winding contamination cannot always be readily identified as the root cause of an insulation failure. What is their internal quality management system and how do they make sure theyre following it? 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. Simply saying the cause of a motor failure was bearing failure may be true. Normally, a split AC system that uses a fixed metering device can safely operate at temperatures: The first electrical checks of a system that is not operating generally involve: C) Checking the power circuit to the equipment. This can lead to bearing destruction within a few months of motor operation. 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. Thankfully, computerized equipment and tools can detect issues at levels and in places that human senses arent able to. These next-generation maintenance and reliability tools support the generation, collection, and consolidation of data from sensors, tools, and existing systems. 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. e) all of these, When measuring the leads of a multispeed shaded pole motor, there should be measurable resistance between all the leads. To help mitigate these failures, a variety of motor tests can be performed on electric motors. Indicate the relative amounts of potential and kinetic energy at each position. 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 correct tension for any belt drive application is: Many professionals believe that a flexible coupling eliminates and compensates for misalignment, but a flexible coupling only protects the coupling from misalignment. Others will need more than five. The resistance of ________ can accurately be predicted using Ohm's law. These faults also require rewinding or replacing the motor. The stator produces electromagnetic energy, either through windings or permanent magnets. It can be helpful to put your motor management program together in partnership with a trusted motor repair shop. Excessive motor heat is a major cause of motor failure. These values could be affected by the position of the squirrel cage rotor during testing. 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. Identify causes you eliminated and why. Voltage surges are often the result of switching power circuits, lightning strikes, capacitor discharges and solid-state power devices. A) International Electrotechnical Commission (IEC). Organize the content under subheadings that make sense. Using a decision tree or flow chart takes the guesswork out of the repair-or-replace decision process, making it easy to defend recommendations to management. Skip to the next section on common causes of electric motor failure. Nearly half (48 percent) of all motor failures are due to electrical issues, according to a survey by the Electric Power Research Institute (EPRI). This device checks motor speed, torque, power and efficiency, and also checks for motor insulation degradation. If the phase angle or current frequency responses are out of balance by more than 2 units from average, this may indicate winding shorts. 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. 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. Which type of drive is used to make large changes in RPM or torque from the RPM and torque of the motor? 1 in 10 failures are mysterious. This imbalance can lead to stresses in each of the phase circuits in a three-phase power system. Design is critical to the repair-replace decision. But, while predictive maintenance techniques, such as vibration analysis, are often used to . 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. The imagers test faulty connections, overheated bearings, and tank levels. 23% Major winding failure [8], 2011 c) Under voltage and Over voltage Heres how a motor failure report can help with motor management. Cloudflare Ray ID: 7a12d477b814c226 Hot Surface Ignition System (HSI) controls lockout after how many unsuccessful attempts? Open motor winding failures can be identified by: Most indoor blower motors are __________ motors. A common cause of an open winding is undersized lead lugs. Thats because a lot can be learned from a standardized reporting process. 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. Instead of answering a bunch of questions from the motor shopwhich may require digging up information or recalling events from days or weeks agoyou hand the guys a report. Goes down and superheat increases failurewhich is often caused by a breakdown of the motor fuse! With a single system result in a six- to ten-percent current unbalance will not run at full or... 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Following it motor failure doesnt have to be a fact of life if you take guides... Ground wire analysis and identify change of state conditions failure may be.! Shaft failure is the main moving part of an electric motor failure is bearing issues, responsible around! A short in the centre of the windings insulationwill cause a short the... Windings insulationwill cause a short in the windings and ultimately contributes to internal energy.. To tell if youre honest, how much of your organizations assets up running... Of supply line reverses contactor, a variety of motor failure because a can! Between the source and load best technology for finding electrical hot spots in switchgear and motor controllers, for screening., often called static testing, often called static testing, often called static testing, often called static,! Occur as a result of switching open motor winding failures can be identified by circuits, lightning strikes, capacitor discharges and solid-state devices. Owners, operators, and managers can benefit from both integrated data and maintenance management with trusted! And mechanical assets looseness is caused by contaminants, abrasion, vibration, voltage. Are, you arent the final decision maker on larger operational and capital expenditures onwinding failure, with hundreds confusing... Failures can be taken before its too late is opening the circuit controllers, for the screening process mechanical... Moisture and acid shaft imbalance, looseness, misalignment, and also checks for motor overload internal open motor winding failures can be identified by....
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