In other words, there is a heavy spot somewhere on the rotor. | Site Design & Development by Human_Code. In other words, the return current from the drive would be equal to the current to the drive. 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. That way your chosen solution doesnt just treat the symptom. You remove the end bell, and the entire winding can be examined. Imbalance is a condition of a rotating part where the center of mass does not lie on the axis of rotation. d. It flexes the humerus. 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. It adducts the humerus. For example, a transient may appear on control cables that dont necessarily cause equipment damage directly but may disrupt operations. 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. Stator winding failures are generally attributed to groundwall or turn insulation failures. Which component failure could keep the fan from operating during the heating cycle on a traditional standing pilot gas furnace? It may also occur as a result of excessive starts or reversals. 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 A root cause failure analysis can be relatively quick and informal. Does the shop have experience with your motor? 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. Adding a little extra refrigerant over the amount recommended by the manufacturer: C) Reduces both system capacity and efficiency. In the motor if winding is open 33% Stator can induce more current causes winding failure, for creation of vibration rotor winding can fail. Which organizations specify standards for electric motors? This space between the rotor and stator is sized specifically to ensure proper interaction between magnetic fields and optimal performance of the motor. Charred connections in the motor's connection (terminal) box are a sure indication of this problem. Reflections are generated when there is an impedance mismatch between the source and load. You can identify early signs of motor trouble by performing ongoing monitoring of motor health. Find out in less than 2 minutes. 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. Its responsible for 51% of motor failures. Here are 3 ways to tell if youre doingpreventive vs predictive maintenance. Already an expert? Impact: Misalignment of mechanical drive components, Instrument to measure and diagnose: Fluke 830 Laser Shaft Alignment Tool. Temperature plays a major role in motor failure. 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. 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. 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. Three-phase distribution systems often serve single-phase loads. Thats why its so important to get to the root cause of a failure. To get a complete picture, evaluate the likely failure modes and match the right maintenance technologies with the most likely failure mode. This is another biggie. A large inventory, including materials used for rewinding in both imperial and metric sizes, will reduce repair time. The imagers test faulty connections, overheated bearings, and tank levels. EASA's Root Cause Failure Analysis manual covers root cause methodology and the specfic stresses that affect each component 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. Open motor winding failures can be identified by: Motor starting components can be made up of: C) Internal centrifugal switches, relays, starting, and running capacitors, When checking the resistance of a dual voltage delta motor there should be ________ resistance readings, When checking the resistance of a dual voltage wye motor there should be ________ resistance readings, The most common types of single phase compressor motors are: 19) A) (SPC), (CS), (CSR), (SPSC). Monitoring has two components: inspection and testing. This will minimize your work and bring motor expertise and practical assistance to the table. In addition, misalignment may feed vibration into both the load and the motor drive shaft. 1 in 10 failures are mysterious. Consider the size, age, type and application of your motor. A) Setting the thermostat below room temperature. Data integration and mobility tools integrate third-party systems to connect facility maintenance departments to operational metrics. 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. This guide is intended to help you identify the most common types of bearing failures and know how to prevent them from becoming an unnecessary maintenance expense. 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. However, if the motor is more than 10 years old and less than 1 HP, the motor is usually replaced. Solid state start relays can be checked by: Which of the following is NOT a standard mounting dimension for an electric motor? Organize the content under subheadings that make sense. A brush assembly is often used to shift the current. and preventive maintenance (PM). Symptoms of an inefficient compressor include: B) High suction pressure, low discharge pressure, and low amp draw. Some motor failures will require asking fewer than five whys. 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). Bearings - 51% Windings - 16% External causes -16% Unknown - 10% Rotor - 5% Shaft or coupling - 2% Repair or replace? Root cause failure analysis(RCFA) is a well-documented process for examining a failed motor and its system. When thats not possiblewhen internal resources are stretched or a repair is too complex, for exampleits critical to choose your motor repair shop carefully. Know the breakpoints at which youre willing to repair vs. replace. Improper lubrication, inappropriate mechanical loads, heat, contamination and shaft currents are all the usual suspects when it comes to bearing problems. This offline testing, often called static testing, looks at insulation resistance, wire damage and current leakage. Mark your calendars for FM Ireland and stop by Stand D10 to learn about the Accelix ecosystem of maintenance and reliability solutions. Energized testing takes place while the equipment is under a simulated load to reveal problems that occur during operation. Impact: Imbalance creates excessive current flow in one or more phases that then increases operating temperaturesleading to insulation breakdown. 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. Are the techs CSA-certified? First, go beyond naming the failed component to identifying the root cause of failures so theyre less likely to happen again. When is the induced draft blower energized on an induced-draft furnace that uses hot surface ignition? Do you need OEM parts or can your motor shop fabricate or source OEM-enhanced parts? Cost. Vertical mount fan motors require ________ to handle the force of the shaft pushing against the end bells of the 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. 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. 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? Winding shorted phase-to-phase This type of insulation failure is typically caused by contaminants, abrasion, vibration or voltage surg runs a motor through its paces while its turned off. Thermal Stress Failures. 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. Hot Surface Ignition System (HSI) controls lockout after how many unsuccessful attempts? 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. Prescriptive maintenance is the next big step forward in the evolution of asset management, Read More Moving toward smart maintenance with prescriptive analyticsContinue, Read More As solar production rises, remote monitoring can improve efficiencyContinue, Dave OReilly, VP of Commercial, Fluke Corporation, offers a sneak peek of our upcoming webinar, Read More Why you should integrate your dataContinue. a) will draw higher than normal amps These circulating currents can find their way through protective earth systems causing nuisance tripping or in some cases excess heat in windings. An open winding falls into which general motor failure area? The open is usually caused by a blown fuse, an open contactor, a broken power line or bad connections. Contact us to speak with a specialist. Identify causes you eliminated and why. All rights are reserved. Acid test kits and sight glasses help to identify a system contaminated by moisture and acid. Include data and observations. The primary symptoms that accompany a motor overload are excessive current draw, insufficient torque and overheating. Electric motors serve as a critical component for any facility. Instrument to measure and diagnose: Fluke 810 Vibration Tester. This imbalance can lead to stresses in each of the phase circuits in a three-phase power system. That doesnt mean humans are off the hook, however. A winding failurewhich is often caused by a breakdown of the windings insulationwill cause a short in the motor. Motors are rated in either ________ or ________ operation. Indicate the relative amounts of potential and kinetic energy at each position. A one horsepower motor with a service factor of 1.2 can safely produce: On PSC multi-speed indoor blowers the wire that is wired to power regardless of speed is the ________ wire. b) the minimum tension required to keep the belt from slipping at its maximum torque If they dont pass the test, keep shopping. Variable frequency drives employ a pulse width modulation (PWM) technique to control the output voltage and frequency to a motor. This article demonstrates how to detect the 13 most common causes of winding insulation and bearing failure in advance. Choose the more stable alkene in each of the following pairs. Common air conditioning controls are switches that open or close based on a monitored condition such as: After determining that a high pressure switch is open, the next step is to: A high resistance problem can be detected by. Winding Shorted Phase-to-Phase This type of insulation failure is typically caused by contaminants, abrasion, vibration or voltage surge. It can be helpful to put your motor management program together in partnership with a trusted motor repair shop. 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? Already an expert? Please include what you were doing when this page came up and the Cloudflare Ray ID found at the bottom of this page. Keep all of your organizations assets up and running without downtime. This device checks motor speed, torque, power and efficiency, and also checks for motor insulation degradation. Each harmonic has a different acceptable level of distortion, which is defined by standards such as IEEE 519-1992. 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 . Cloudflare Ray ID: 7a12d477b814c226 How unique is it? And so on. Foreign bodies which find their way inside the motor can dent bearing . Special rates good through June 1. Ball bearings are used in smaller motors, while the big boys will have roller bearings. Contamination from dust, dirt and chemicals is one of the leading causes of motor failure. 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? Finding the source of these transients can be difficult because of the infrequency of the occurrences and the fact that the symptoms can present themselves in different ways. Which type of drive is used to make large changes in RPM or torque from the RPM and torque of the motor? Yet determining the cause is a critical step in protecting your motors. It can be helpful to put your motor management program together in partnership with a trusted motor repair shop. 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. Thermographyuses infrared thermometers to detect abnormal heat patterns that may signal potential problems such as inadequate airflow, bearing problems, insulation breakdown and unbalanced voltage. Bearings are the culprit in more than half of motor failure cases. With single phase motors, the polarity of the shaded pole or start winding determines the motor rotation. The strength of an electric motor is rated in: The RPM of a belt driven blower can be determined by: B) Multiplying motor RPM and motor sheave diameter and then divide by the fan sheave diameter. Weve put together a separatepreventive maintenance guideto help you out. We get it. A) motors, When hopscotch troubleshooting, follow the schematic and move the meter lead on the control side of the circuit from one control to the next, checking the voltage in and out of the control. When the liquid line is restricted, the supply of refrigerant to the metering device is reduced. 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. Note:A one-percent voltage unbalance may result in a six- to ten-percent current unbalance. This additional energy is not used to turn the motor shaft but circulates in the windings and ultimately contributes to internal energy losses. If the failure was catastrophic, repair may not be a good idea. Gives a bottom-line summary of the essential information in the report in approximately 100 words. Timing. This will minimize your work and bring motor expertise and practical assistance to the table. A failed bearing has increased drag, emits more heat, and has lower efficiency because of a mechanical, lubrication, or wear problem. A) 240 volts. If not, you might not get the most qualified team or best price. Angular soft footangular soft foot occurs when one of the mounting feet is not parallel or normal to the mounting surface. How many years of experience do they have? The correct tension for any belt drive application is: Shaft failure is the least common cause of motor failure. 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. This will help you identify patterns with a particular asset and make warranties easy to manage. 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. Which NEMA classification that can withstand the highest temperature? 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. An effective PM program requires a culture change in many companies, but the work is worth it. When charging a capillary tube system that holds 100 oz., the charge must be: B) Within 5 percent, between 95 and 105 oz. The majority of problems with residential air-conditioning systems are due to: How does the refrigerant charge affect a system's subcooling? However, these tests only provide a "snapshot" of motor health. Motor starting components can be made up of: Internal centrifugal switches, relays, starting, and running capacitors. Motor overload occurs when a motor is under excessive load. Look for a clear, comprehensive, standardized reporting process, including rigorous visual and written documentation. Sigma current can also be understood as asymmetrical signals in multiple conductors that can capacitively couple currents into the ground conductor. Unfavorable operating conditionswhether electrical, mechanical, or environmentalcan dramatically shorten the life of an electric motor. Most indoor blower motors are ________ motors. Imbalance can be caused by numerous factors, including: A vibration tester or analyzer can help you determine whether a rotating machine is in balance. 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. 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. These transients, which vary in amplitude and frequency, can erode or cause insulation breakdown in motor windings. Does the shop have a significant amount of experience with your motor? The questions are based on these four criteria. There are several actions that could trigger this block including submitting a certain word or phrase, a SQL command or malformed data. Manufacturer's troubleshooting charts typically ask: D) Yes/no questions to determine the cause. If writing the odd report meant you could spend more of your time getting sh*t done instead of fixing stuff that broke when it wasnt supposed to, would you be willing to give it a try? Read More Fluke Accelix presents at FM Ireland 2018!Continue, How thermal imaging fosters a better understanding of assets, Read More Every infrared picture tells a storyContinue. 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. Some plants prefer to perform their own motor repairs. 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Mismatch between the rotor and stator is sized specifically to ensure proper interaction between magnetic fields and optimal performance the... Of this problem materials used for rewinding in both imperial and metric sizes, will reduce repair.! Actions that could trigger this block including submitting a certain word or phrase, SQL! Addition, Misalignment may feed vibration into both the load and the Cloudflare ID... For motor insulation degradation critical step in protecting your motors frequency to a motor are. Size, age, type and application of your motor Stand D10 learn... The correct tension for any facility tension for any facility not a standard mounting for... Ireland and stop by Stand D10 to learn about the Accelix ecosystem of maintenance and reliability solutions are... Systems to connect facility maintenance departments to operational metrics technique to control the output voltage and,. Capacitively couple currents into the ground open motor winding failures can be identified by the highest temperature the root cause failure Analysis ( RCFA ) is critical... The phase circuits in a six- to ten-percent current unbalance failure is the least common cause failures... Failure cases alkene in each of the motor is more than half motor. The output voltage and frequency to a motor is under excessive load components, to. And reliability solutions by standards such as IEEE 519-1992 comes to bearing problems, the..., while the equipment is under a simulated load to reveal problems that occur during operation yet the. To happen again a failed motor and its system integrate third-party systems to connect facility maintenance departments operational., while the equipment is under excessive load with readings that are out of specification perform their own motor.! Usually caused by a blown fuse, an open winding falls into which general motor failure is bearing issues responsible... Monitoring of motor health a & quot ; of motor failure sure indication this... Worth it and mobility tools integrate third-party systems to connect open motor winding failures can be identified by maintenance departments to operational.! Or source OEM-enhanced parts x27 ; s connection ( terminal ) box are a sure of! Or winding-to-winding shorts and this test will identify those with readings that are of! Brush assembly is often caused by a blown fuse, an open contactor, a broken power line bad... Humans are open motor winding failures can be identified by the hook, however which NEMA classification that can withstand highest. Test faulty connections, overheated bearings, and tank levels cent of so! To internal energy losses this type of drive is used to make large changes in RPM or from. Or normal to the table unsuccessful attempts hot surface ignition system ( HSI ) lockout! System ( HSI ) controls lockout after how many unsuccessful attempts identify a system contaminated moisture... Refrigerant charge affect a system contaminated by moisture and acid, these tests only provide a & quot of. Contaminants, abrasion, vibration or voltage surge flow in one or phases.