Impact: Imbalance creates excessive current flow in one or more phases that then increases operating temperaturesleading to insulation breakdown. Identify causes you eliminated and why. Opens are indicated by infinite resistance or impedance reading. B) Call the equipment supplier and provide the system model numbers. 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. 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); An effective PM program requires a culture change in many companies, but the work is worth it. All photographs are copyrighted 1985-2019byEASA. Impact: Arcing across bearing surfaces create pitting and fluting resulting in excessive vibration and eventual bearing failure. c. It abducts the arm. 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. Capture and document critical measurements at installation, before and after maintenance and on a routine basis. Extent of failure. Insulation failures are typically caused by contaminants, abrasion, vibration, or voltage surge. Re-state what you felt caused the failure. Thermal deterioration of the insulation in all phases of the stator winding typically is caused by load demands exceeding the rating of the motor. Here are some of the more common motor tests to perform regularly as part of your early warning system. d. It flexes the humerus. Next up is advice on troubleshooting, fault testing, motor failure reporting and decision-making, including when to call in a motor shop. Nearly all air conditioning condenser fans are ________ motors. Timing. In the case of an overloaded motor individual motor components including bearings, motor windings, and other components may be working fine, but the motor will continue to run hot. 4. A) Fan RPM = Motor RPM Motor Sheave Diameter Fan Sheave Diameter. Always keep accurate and detailed records of your inspection and testing and keep them in one place to make it easy to identify trends and keep track of actions taken. 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. If there is no resistance or the resistance is uneven, the motor is likely faulty. D) The large temperature drop indicates the airflow is less than required. 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. That way you can save your bearing next time, instead of simply having it fail again. Using your existing staff, and scaling as necessary, you can implement without costly retrofitting and large IT infrastructure investments. 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. They also enhance remote monitoring capabilities through connected devices including desktop, tablet, or smartphone. 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. Which NEMA classification can withstand the highest temperature? What is their internal quality management system and how do they make sure theyre following it? Open motor winding failures can be identified by: A) Zero resistance reading B) Infinite resistance reading C) Measurable resistance reading D) All of the above B) Infinite resistance reading Motor starting components can be made up of: A) Starting and running capacitors only B) Internal and external centrifugal switches only 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. c) 1/64th inch deflection per 1 inch span between drive shaft and driven shaft Which of the following is (are) true concerning the pectoralis major? Failuresare shown here to help identify the causes of failure, so that, where possible, preventative measures may be taken. Should we repair the motor or replace it? Impact: Mysterious circuit trip due to protective earth current flow, Instrument to measure and diagnose: Fluke 190-204 ScopeMeter Test Tool. To keep operations running smoothly, implementing preventive maintenance programs leads to a predictive and prescriptive maintenance future. How long have the staff been there? The open is usually caused by a blown fuse, an open contactor, a broken power line or bad connections. If they can't, lubricate them. Its responsible for 51% of motor failures. 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. Looseness and bearing failures. 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. Maintenance software and data gathering devices that integrate with third-party solution providers are ideal to accomplish this. Shaft failure is the least common cause of motor failure. Motor control systems are being utilized in critical processes throughout manufacturing plants. If the failure was catastrophic, repair may not be a good idea. When there is high resistance across the contacts when they are closed: C) A voltage drop will be read across the contacts. If you know the basics of electric motor function, including the names of the main parts of both AC and DC motors, youll get the most out of the rest of this guide. How long will it take to get the motor repaired? It can also detect the presence of dirt or moisture. Why is that, and which isotope is located near the axis? 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. Vibration and alignment tools are the best technology for diagnosing mechanical faults in rotating machines. 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. 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. This is another biggie. See more information related to AC and DC Windings in EASA's Resource Library. At the simplest level, all three phases of voltage should always have the same magnitude. 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. 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. 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. However, if the motor is more than 10 years old and less than 1 HP, the motor is usually replaced. Note:Under-voltage and over-voltage (exceedingNEMAstandards) will result in the same type of insulation deterioration. Performance & security by Cloudflare. Always ensure the motor thermal protector has not opened. If not, you might not get the most qualified team or best price. Switching power circuit, capacitor discharges, or solid-state power devices can also cause this type of motor winding damage Windings are made from insulated metal wire, usually copper but sometimes aluminum, that are laid in coils and wound around either the rotor or the stator. 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). Winding shorted phase-to-phase This type of insulation failure is typically caused by contaminants, abrasion, vibration or voltage surg 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. When charging a capillary tube system that holds 100 oz., the charge must be: B) Within 5 percent, between 95 and 105 oz. The correct tension for any belt drive application is: Explain your reasoning. It may also occur as a result of excessive starts or reversals. A) Adding refrigerant increases the system subcooling. The open is usually caused by a blown fuse, an open contactor, a broken power line or bad connections. 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. Sigma currents are essentially stray currents that circulate in a system. Whats the lead time on a new motor? Why. 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? This type of insulation failure is typically caused by contaminants, abrasion, vibration or voltage surge. Next up is advice on troubleshooting, fault testing, motor failure reporting and decision-making, including when to call in a motor shop. takes place while the equipment is under a simulated load to reveal problems that occur during operation. How unique is it? It treats the underlying condition that created the situation in the first place. 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. Infrared imagers are the best technology for finding electrical hot spots in switchgear and motor controllers, for the screening process and mechanical assets. The Effect of Repair/Rewinding on Premium Efficiency/IE3 Motors. Weve come up with these 6 questions to ask deciding whether to repair or replace your electric motor. Impact: Shaft misalignment and subsequent stresses on rotating components, leading the premature failures. The questions are based on these four criteria. (If youve had small children in your life, youll also have flashbacks.) 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. There are several actions that could trigger this block including submitting a certain word or phrase, a SQL command or malformed data. Why doesn't uranium ore spontaneously undergo a chain reaction? A single-phased winding failure is the result of an open in one phase of the power supply to the motor. 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. a. 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. Every robust PM program will includekeyperformance indicatorsso you can measure success and make improvements. Do they follow the ANSI/EASA AR100 best practices? When ohming components on the system, it is important to: How is the subcooling of an air-conditioning system affected by a restriction in the liquid line? Your motor shop can help you. Your IP: Potential relays measure the back ________ developed across the ________ winding to operate the relay. But anyone in the biz knows that behind that question is a whole lot of hemming and hawing, made worse by pressure cooker environments and a lack of information. 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 . 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