Impact: Shaft misalignment and subsequent stresses on rotating components, leading the premature failures. Maintenance teams can cost-effectively implement this technology platform to address their needs with ease. Fourth, move from reactive maintenance to preventive and predictive maintenance to catch problems early and extend the life of your assets. This report may come from your motor shop. In either case, any soft foot condition must be discovered and remedied before proper shaft alignment can be achieved. Fluke Accelix presents at FM Ireland 2018! The knee-jerk conclusion about the cause of the motor failure is often very different from the conclusion a tech will reach after writing a formalized report. Opens are indicated by infinite resistance or impedance reading. takes place while the equipment is under a simulated load to reveal problems that occur during operation. However, these tests only provide a "snapshot" of motor health. Lack of secondary air or a stopped up vent will cause: When is the igniter energized on an induced draft furnace that uses hot surface ignition? That way you can save your bearing next time, instead of simply having it fail again. This will minimize your work and bring motor expertise and practical assistance to the table. 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 resistance of ________ can accurately be predicted using Ohm's law. In this case, different is better. Re-state what you felt caused the failure. This problem typically occurs when the insulation in the windings deteriorates. The benefits of detecting, identifying, and evaluating electric motor abnormalities are decreased motor failures and less unexpected downtime. Note:A one-percent voltage unbalance may result in a six- to ten-percent current unbalance. A root cause failure analysis can be relatively quick and informal. Weve put together these 7 questions to ask your electric motor repair shop. These next-generation maintenance and reliability tools support the generation, collection, and consolidation of data from sensors, tools, and existing systems. 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. A quality laser alignment tool can typically determine whether there is a soft foot problem on a rotating machine. Lets take bearing failure, for example. Youll notice there are no solutions or implementation sections. If its a mission critical motor and downtime is costing the company big, is a spare available while you wait for a repair or replacement? 23% Major winding failure [8], 2011 c) Under voltage and Over voltage A simple way to do a root cause failure analysis is using the 5 Whys technique. Whos got time to write a motor failure report? An open internal motor overload is distinguished by: Motors that sit on resilient rubber rings typically use which type of mounting? Include data and observations. An open winding falls into which general motor failure area? Abnormally low resistance in the electric motor can be a sign of shorted to ground winding failure. Does the shop have experience with your motor? Why doesn't uranium ore spontaneously undergo a chain reaction? Bearings are the culprit in more than half of motor failure cases. Will the shop do the work themselves, or will they outsource it? The open is usually caused by a blown fuse, an open contactor, a broken power line or bad connections. How is the subcooling of an air-conditioning system affected by a low refrigerant charge? This condition can create a frustrating situation in which tightening the mounting bolts on the feet introduces new strains and misalignment. What causes the little pops and ticking that can be heard in some furnaces before the blower comes on? This offline testing, often called static testing, looks at insulation resistance, wire damage and current leakage. Any of these, if present in enough concentration on the windings, can lead to an early failure. 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. Copyright 2016-2021 Duke Electric. Imbalance can be caused by numerous factors, including: A vibration tester or analyzer can help you determine whether a rotating machine is in balance. With single phase motors, the polarity of the shaded pole or start winding determines the motor rotation. , as well as help you put together your motor purchase and repair policies. In addition, misalignment may feed vibration into both the load and the motor drive shaft. What is a common symptom of a severely restricted filter drier? This is another biggie. If the reading is infinite, your motor should be fine. 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. 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. Transient voltages can come from several sources either inside or outside of the plant. Energized testing takes place while the equipment is under a simulated load to reveal problems that occur during operation. Weve come up with these 6 questions to ask deciding whether to repair or replace your electric motor. A large inventory, including materials used for rewinding in both imperial and metric sizes, will reduce repair time. The open is usually caused by a blown fuse, an open contactor, a broken power line or bad connections. Another common fault stems from mechanical rubs, which can be the result of looseness of the motor shaft and/or the motor bearings. If they dont pass the test, keep shopping. The failure mechanism involves the gradual development of a weakness in the insulation. 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. The expected temperature drop through a direct expansion evaporator coil: D) Can be determined with a chart supplied by the coil manufacturer. The questions are based on these four criteria. But the down-the-road benefits will pay off big. Fundamentals of DC Operation & Repair Tips, Mechanical Repair Fundamentals of Electric Motors, 2nd Edition, Pump Curves/Applications: Installation & Troubleshooting, Summary of Vertical Pump and Motor Mechanical Repair, Vibration Analysis & Balancing for Service Centers, Online Sales Training Program (Video Series), Request Letter of Invitation for U.S. Visa, Getting the Most from Your Electric Motors. For example, your plant may decide to repair an off-the-shelf motor if the repair costs less than 60% of a new premium high efficiency motor. Each harmonic has a different acceptable level of distortion, which is defined by standards such as IEEE 519-1992. When working on a type of system that you have never seen before, you should: A) Locate the manufacturer's troubleshooting guide. b. The machines provide the data. 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 . 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. quent compressor failure can result within a few hours. All rights are reserved. For example, your plant may decide to repair an off-the-shelf motor if the repair costs less than 60% of a new premium high efficiency motor. Some plants prefer to perform their own motor repairs. Excessive motor heat is a major cause of motor failure. To help mitigate these failures, a variety of motor tests can be performed on electric motors. Extent of failure. runs a motor through its paces while its turned off. Various factors, such as overheating, physical damage . Are the techs CSA-certified? Describe how energy changes as a ball is thrown in the air. If they can't, lubricate them. Motors are rated in either ________ or ________ operation. Cloudflare Ray ID: 7a12d477b814c226 | Site Design & Development by Human_Code. 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. Winding shorted phase-to-phase This type of insulation failure is typically caused by contaminants, abrasion, vibration or voltage surg The suction pressure on a split AC system that is running with an excessive evaporator heat load: The manufacturer's data on a split AC system indicates that the normal temperature drop should be 15F at the current operating conditions. This imbalance can lead to stresses in each of the phase circuits in a three-phase power system. Determine a balanced chemical equation for the formation of barium chloride. When a plant has adopted a preventive maintenance mindset, engineers and technicians are supported to monitor motors and troubleshoot problems before they cause a failure. Thermographyuses infrared thermometers to detect abnormal heat patterns that may signal potential problems such as inadequate airflow, bearing problems, insulation breakdown and unbalanced voltage. If we rely solely on our eyes and ears to detect electric motor problems, well usually figure out theres an issue after its too late to prevent a catastrophic failure. Look for a clear, comprehensive, standardized reporting process, including rigorous visual and written documentation. Three-phase distribution systems often serve single-phase loads. Thermal Stress Failures. That way your chosen solution doesnt just treat the symptom. In other words, there is a heavy spot somewhere on the rotor. 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 causes electric motors to fail? A common cause of an open winding is undersized lead lugs. Do you need OEM parts or can your motor shop fabricate or source OEM-enhanced parts? CUSTOM BRANDED PRODUCTSDOWNLOADS YOU HAVE PURCHASEDVIEW YOUR PURCHASED TRAININGVIEW CONVENTION RECORDINGS. C) Unusual airflow restrictions in the duct. Timing. 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. (If youve had small children in your life, youll also have flashbacks.) . A one horsepower motor with a service factor of 1.2 can safely produce: Manufacturers often recommend adding what component to split systems with unusually long refrigerant lines? A) Setting the thermostat below room temperature. Motor overload occurs when a motor is under excessive load. Heres how to set your motors up for success, not failure. You remove the end bell, and the entire winding can be examined. D) After the draft switch closes to prove the draft. To keep operations running smoothly, implementing preventive maintenance programs leads to a predictive and prescriptive maintenance future. Shaft failure is the least common cause of motor failure. Sounds simple. Most indoor blower motors are ________ motors. Failures disrupt business operations, decrease productivity, and adversely impact a companys bottom line. Switching power circuit, capacitor discharges, or solid-state power devices can also cause this type of motor winding damage 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 most common types of single phase compressor motors are: Permanent split capacitor (PSC), capacitor start (CS), capacitor start/capacitor run (CSCR), and split phase, Motors with shunted field windings: The life of a three-phase stator winding can be shortened dramatically when the motor is exposed to unfavorable operating conditions electrical, mechanical or environmental. The primary symptoms that accompany a motor overload are excessive current draw, insufficient torque and overheating. 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. More than one response required. Many professionals believe that a flexible coupling eliminates and compensates for misalignment, but a flexible coupling only protects the coupling from misalignment. 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. Rotating looseness is caused by excessive clearance between rotating and stationary elements of the machine, such as in a bearing. Need an Accredited service center?Find a service center that has proven they repair electric motors in accordance with ANSI/EASA's AR100. 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. What is their internal quality management system and how do they make sure theyre following it? The winding failures illustrated here are typical of what can happen is such circumstances. Yet determining the cause is a critical step in protecting your motors. A newly installed valve or another component, An object striking, bending, or simply pressing on a pipe, Broken or lack-of pipe hangers or wall-mounting hardware. 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. 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. And those issues will have another cause. If the motor is less than 1/8 HP, it is almost always replaced. This website is using a security service to protect itself from online attacks. 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. Why is that, and which isotope is located near the axis? Impact: Arcing across bearing surfaces create pitting and fluting resulting in excessive vibration and eventual bearing failure. Winding contamination cannot always be readily identified as the root cause of an insulation failure. Then we identify the 5 common causes of industrial motor failure.