Then we identify the 5 common causes of industrial motor failure. Whos got time to write a motor failure report? Which of the following formulas can be used to calculate fan speed (RPM)? c) 1/64th inch deflection per 1 inch span between drive shaft and driven shaft 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? 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. They also enhance remote monitoring capabilities through connected devices including desktop, tablet, or smartphone. Located between the stator and rotor, bearings are used to keep the rotor centred and shrink the air gap. Some motor failures will require asking fewer than five whys. to ask deciding whether to repair or replace your electric motor. Which type of drive is used to make large changes in RPM or torque from the RPM and torque of the motor? This can lead to bearing destruction within a few months of motor operation. The benefits of detecting, identifying, and evaluating electric motor abnormalities are decreased motor failures and less unexpected downtime. Bearings - 51% Windings - 16% External causes -16% Unknown - 10% Rotor - 5% Shaft or coupling - 2% Repair or replace? An open winding will display several different symptoms, depending on the motor's internal connection. Butdont screw it up. Uneven mass in motor windings and other wear-related factors. Stator winding failures are generally attributed to groundwall or turn insulation 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. Explain why a sample of iron(III) sulfate is uncharged. For this reason, it makes sense to begin your troubleshooting by checking for motor overload. It may also occur as a result of excessive starts or reversals. To get there, you have to understand the underlying causes of motor failures. Whats the lead time on a new motor? 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 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. A) Setting the thermostat below room temperature. What is a common symptom of a severely restricted filter drier? Reproduction of these photographs by print or electronic means is prohibited. . Some harmonic distortion of the current is normal on any part of the system serving electronic loads. Start reaping the benefits of membership today. Which of the following is (are) true concerning the pectoralis major? When charging a capillary tube system that holds 100 oz., the charge must be: B) Within 5 percent, between 95 and 105 oz. c) are hard to detect A failed bearing has increased drag, emits more heat, and has lower efficiency because of a mechanical, lubrication, or wear problem. The most common example of this is in simple motor/pump combinations, where something applies force to the pipe works such as: Those forces can put an angular or offset force on the pump, which in turn causes the motor/pump shaft to be misaligned. A common cause of an open winding is undersized lead lugs. And those issues will have another cause. Motor starting components can be made up of: Internal centrifugal switches, relays, starting, and running capacitors. Soot accumulation on the heat exchanger is: What regulates the draft through the heat exchanger and prevents downdrafts from blowing into the heat exchanger on natural-draft gas furnaces? quent compressor failure can result within a few hours. 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. Youll notice there are no solutions or implementation sections. Winding insulation breakdown and bearing wear are the two most common causes of motor failure, but those conditions arise for many different reasons. a) will draw higher than normal amps Need an Accredited service center?Find a service center that has proven they repair electric motors in accordance with ANSI/EASA's AR100. These transients, which vary in amplitude and frequency, can erode or cause insulation breakdown in motor windings. Any change in trend line of more than +/- 10% to 20% (or any other % determined, based on your system performance or criticality) should be investigated to root cause to understand why the issue is occurring. 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. 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 . These circulating currents can find their way through protective earth systems causing nuisance tripping or in some cases excess heat in windings. | Site Design & Development by Human_Code. Describe how energy changes as a ball is thrown in the air. The most common mechanical faults are shaft imbalance, looseness, misalignment, and bearings. This condition can create a frustrating situation in which tightening the mounting bolts on the feet introduces new strains and misalignment. If the motor is less than 1/8 HP, it is almost always replaced. Always ensure the motor thermal protector has not opened. Some plants prefer to perform their own motor repairs. What causes the little pops and ticking that can be heard in some furnaces before the blower comes on? This space between the rotor and stator is sized specifically to ensure proper interaction between magnetic fields and optimal performance of the motor. Should we repair the motor or replace it? Motor windings account for about 32% of all AC electric motor repairs. 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. 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. 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. B) Call the equipment supplier and provide the system model numbers. 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. Click to reveal Is it well suited for the application, or is it time to spec a new motor that can better accomplish what your process demands? This imbalance can lead to stresses in each of the phase circuits in a three-phase power system. 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. Note:A one-percent voltage unbalance may result in a six- to ten-percent current unbalance. The questions are based on these four criteria. 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. (Note: almost all misalignment is compound misalignment, but practitioners talk about misalignment as the two separate types because it is easier to correct a misalignment by addressing the angular and parallel components separately.). 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. Excessive motor heat is a major cause of motor failure. 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. c. It abducts the arm. If they dont pass the test, keep shopping. They can test correct shaft alignment, imbalances, looseness, misalignment, and bearings. 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. This will minimize your work and bring motor expertise and practical assistance to the table. If they can't, lubricate them. Instrument to measure and diagnose: Fluke 810 Vibration Tester. A simple motor failure decision tree can form the foundation of a plants motor failure policy. d) can be detected by comparing the actual winding resistance to the motor manufacturer's data 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? That way you can save your bearing next time, instead of simply having it fail again. Energized testing takes place while the equipment is under a simulated load to reveal problems that occur during operation. Keep all of your organizations assets up and running without downtime. These winding failures fall into four major categories related to what causes them: thermal stress, mechanical stress, electrical stress, and environmental stress. How unique is it? Motor design. Find out in less than 2 minutes. A) Adding refrigerant increases the system subcooling. Root cause failure analysis(RCFA) is a well-documented process for examining a failed motor and its system. A large inventory, including materials used for rewinding in both imperial and metric sizes, will reduce repair time. PM has been shown to reduce downtime by as much as 50%. The expected temperature drop through a direct expansion evaporator coil: D) Can be determined with a chart supplied by the coil manufacturer. Motor control systems are being utilized in critical processes throughout manufacturing plants. Already an expert? The motor and insulation tester assure safe operation, prolongs the life of electrical systems and motors. Fluke Accelix presents at FM Ireland 2018! Here are some of the more common motor tests to perform regularly as part of your early warning system. Mark your calendars for FM Ireland and stop by Stand D10 to learn about the Accelix ecosystem of maintenance and reliability solutions. Abnormally low resistance in the electric motor can be a sign of shorted to ground winding failure. Sigma currents are essentially stray currents that circulate in a system. Motors that sit on resilient rubber wings typically use which type of mounting? 195.201.81.185 Physical damage, corrosion, improper installation and excessive loads are often the root cause. Improper lubrication, inappropriate mechanical loads, heat, contamination and shaft currents are all the usual suspects when it comes to bearing problems. 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. Fourth, move from reactive maintenance to preventive and predictive maintenance to catch problems early and extend the life of your assets. Failures disrupt business operations, decrease productivity, and adversely impact a companys bottom line. Thermal deterioration of insulation in one phase of the stator winding. These losses dissipate in the form of heat, which, over time, will deteriorate the insulation capability of the windings. , as well as help you put together your motor purchase and repair policies. To help mitigate these failures, a variety of motor tests can be performed on electric motors. But the down-the-road benefits will pay off big. This report may come from your motor shop. EASA's new streaming sales videos provide relevant and insightful training. A carbon brush probe attachment allows you to measure shaft voltage while a motor is rotating. We wrap it up by looking at the bigger picture, including how to perform a root cause failure analysis, 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. This is another biggie. c) moisture The benefits of these maintenance software tools include: Leveraging these tools and technologies can offer key insights into the health of electric motors. You can identify dead shorts, loose connections and open circuits in coiled windings using a digital multimeter. Connected tools and sensors offer all key stakeholders with access to the data they need. Theres a big difference between reactive maintenance and preventive maintenance (PM). 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. Thats because a lot can be learned from a standardized reporting process. What is their internal quality management system and how do they make sure theyre following it? Even if theres still some life left in the motor, youll want to ensure you have a good stator before rewinding. Lets take bearing failure, for example. Imbalance is a condition of a rotating part where the center of mass does not lie on the axis of rotation. Each harmonic has a different acceptable level of distortion, which is defined by standards such as IEEE 519-1992. Do they follow the ANSI/EASA AR100 best practices? EASA's Root Cause Failure Analysis manual covers root cause methodology and the specfic stresses that affect each component of an electric motor. Unfavorable operating conditionswhether electrical, mechanical, or environmentalcan dramatically shorten the life of an electric motor. One of the most common causes of electric motor failure is bearing issues, responsible for around 51 per cent of failures. Looseness and bearing failures. In fact, Cooper Bussmann says old age causes only 10% of electric motor failures. This is the logical outcome, given what youve written in the rest of the report. and preventive maintenance (PM). 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. Many professionals believe that a flexible coupling eliminates and compensates for misalignment, but a flexible coupling only protects the coupling from misalignment. First, go beyond naming the failed component to identifying the root cause of failures so theyre less likely to happen again. More than one response required. De-energized testing runs a motor through its paces while its turned off. Know the breakpoints at which youre willing to repair vs. replace. Organize the content under subheadings that make sense. 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. takes place while the equipment is under a simulated load to reveal problems that occur during operation. Winding Failures. Include data and observations. Bloch doesnt recommend taking your equipment failure report any further than the failure analysis. Then we identify the 5 common causes of industrial motor failure. 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. It should concisely answer what, where, when, how and possibly why. Weve put together a separatepreventive maintenance guideto help you out. b. Other failures are caused by vibration, physical damage and situations that causes excessive heat. It is made of thin metal sheets, called laminations, instead of being solid, to reduce energy losses. 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. 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. On PSC multi-speed indoor blowers the wire that is wired to power regardless of speed is the ________ wire. 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. Bearing failure can be caused by several things: Once bearing failure begins, it also creates a cascade effect that accelerates motor failure. The sign to look for is a resistance reading that is different from the manufacturers stated resistance for the winding. Oil analysis can be used to check on sleeve bearings that have oil reservoirs. Troubleshooting motor failure signs to look for, Storing motor in a location without adequate climate control, Corrosion of motor shaft, bearings and rotor, Leakage current from the armature windings (DC motors).
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