Voltage surges are often the result of switching power circuits, lightning strikes, capacitor discharges and solid-state power devices. The correct tension for any belt drive application is: Consider the size, age, type and application of your motor. The key is to dive deeper into understanding why the component failed. Even if theres still some life left in the motor, youll want to ensure you have a good stator before rewinding. D) Suction pressure goes down and superheat increases. Plot individual measurements to establish a baseline trend. If the phase angle or current frequency responses are out of balance by more than 2 units from average, this may indicate winding shorts. Click to reveal An open winding falls into which general motor failure area? Why. Sounds simple. 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\. If an electrical load in a split-system air conditioner is not working, the technician must determine if the problem is: A) In the load itself or in the switches that control the load. 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. Contamination. How efficient is the motor that failed? Create an archive reference of measurements to facilitate trend analysis and identify change of state conditions. 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. 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. Skip to the next section on common causes of electric motor failure. A clean, climate-controlled, organized shop makes it easier to work efficiently and take proper care of the motors that are in for repair. Impact: Accelerated wear on rotating components resulting in bearing failure. Motors are used everywhere in industrial environments and they are becoming increasingly complex and technical, sometimes making it a challenge to keep them running at peak performance. Need an Accredited service center?Find a service center that has proven they repair electric motors in accordance with ANSI/EASA's AR100. Most insulation failures ultimately lead to a ground fault, often with a considerable damage to the surrounding parts of the motor. 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. Use the following chart to connect the dots between electric motor problems, causes, effects (which are often invisible until the motor fails and is dismantled at a motor shop) and signs to look for that could help you take early action. The imagers test faulty connections, overheated bearings, and tank levels. Transient voltages can come from several sources either inside or outside of the plant. We've put together a post onwinding failure, with awesome photos courtesy of EASA, if you're looking for examples. Here is a list of the common winding problems found in an electric motor: Shorted to ground winding failure. Imbalance is a condition of a rotating part where the center of mass does not lie on the axis of rotation. Winding shorted turn-to-turn Do you need OEM parts or can your motor shop fabricate or source OEM-enhanced parts? But the down-the-road benefits will pay off big. 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. Infrared sensors can seamlessly integrate with a software platform that gathers data from many other sensor types. Sounds simple. (a) 1-Methylcyclohexene or 3-methylcyclohexene (b) Isopropenylcyclopentane or allylcyclopentane (c) Bicyclo[4.2.0]oct-7-ene or Bicyclo[4.2.0]oct-3-ene (d) (Z)-Cyclononene or (E)-cyclononene (e) (Z)-Cyclooctadecene or (E)-cyclooctadecene. 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. Everyone is busy. How unique is it? If the failure was catastrophic, repair may not be a good idea. Sigma current can also be understood as asymmetrical signals in multiple conductors that can capacitively couple currents into the ground conductor. Electrical failures disrupt the power supply to the motor. Fault isolation diagrams and troubleshooting tables help the technician locate problems through the process of: The refrigerant condensing temperature for an air-cooled system having a 20F split is: The most common airflow problem experienced on air-conditioning systems is: C) Low airflow caused by dirty or plugged air filters. 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. Motors are rated in either ________ or ________ operation. For this reason, it is important to check machine alignment more than just at the time of installationprecision alignment is a temporary condition that can change over time. If they dont pass the test, keep shopping. 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. Winding insulation breakdown and bearing wear are the two most common causes of motor failure, but those conditions arise for many different reasons. Energized testing takes place while the equipment is under a simulated load to reveal problems that occur during operation. Maintenance software and data gathering devices that integrate with third-party solution providers are ideal to accomplish this. While these may appear to be rigorous, they may not achieve the true benefits of a less specific failure report, which is to structure a thinking process. 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. 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? near the wall? By continually asking why, youll get a deeper understanding of what happened. 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. 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. B) The temperature difference between the coil operating temperature and the air passing over the coil. Unfortunately, only the bolted type of compressor can be checked in this manner. More than one choice may apply. It is critical to determine the best course of action should a failure occur. Will the shop do the work themselves, or will they outsource it? Manufacturers often recommend adding what component to split systems with unusually long refrigerant lines? Impact: Decrease in motor efficiency results in added cost and an increase in operating temperatures. In either case, any soft foot condition must be discovered and remedied before proper shaft alignment can be achieved. With the motor running, you can perform dynamic testing to identify issues with temperature, balance and distortion. 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. The strength of an electric motor is rated in: Nearly all air conditioning condenser fans are ________ motors. Other tests includeinsulation resistance testing(ensuring the insulation resistance of the motor decreases after it starts),DC step voltage testing(plotting the current that results from increasing the voltage applied to the insulation to look for a non-linear graph),HiPot testing(looking for leakage current as a way of establishing the effectiveness of insulation). Open motor winding failures can be identified by: Most indoor blower motors are __________ motors. EASA's Root Cause Failure Analysis manual covers root cause methodology and the specfic stresses that affect each component of an electric motor. Well help you select the right product for your needs. Possible solution: It is critical that the motor is kept as cool as possible, ensuring the operating environment is kept cool if possible will help prevent breakdowns. 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. Second, formalize your documentation and reporting so its easy to get all the information about a particular motor to the people that need it. 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. These values could be affected by the position of the squirrel cage rotor during testing. Know the breakpoints at which youre willing to repair vs. replace. 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. In a perfect situation, the sum of the three currents would equal zero. Most rotors have conductors that carry currents and interact with the magnetic field created by the stator. All rights are reserved. Thermal deterioration of insulation in one phase of the stator winding. b) the minimum tension required to keep the belt from slipping at its maximum torque Of that 48 percent, 12 percent can be attributed to rotor problems and 36 percent to winding problems. 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); 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. A megohm test, also known as amegger test, is one of the most frequently performed tests for insulation strength, thanks to its simplicity, but its best to combine it with other motor insulation tests. This is another biggie. Foreign bodies which find their way inside the motor can dent bearing . When you suspect an issue with your electric motor winding, there are three categories of measurements to help identify the likely source of failureselectrical, mechanical, and thermal. Any time a fuse is replaced or a breaker is reset, which of the following should be checked before operating the system? Butdont screw it up. This can lead to bearing destruction within a few months of motor operation. We can see your eyes rolling. This imbalance can lead to stresses in each of the phase circuits in a three-phase power system. A root cause failure analysis can be relatively quick and informal. 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. Thermal deterioration of insulation in one phase of the stator winding can result from unequal voltage between phases. Design is critical to the repair-replace decision. Variable frequency drives employ a pulse width modulation (PWM) technique to control the output voltage and frequency to a motor. 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. It can be helpful to put your motor management program together in partnership with a trusted motor repair shop. 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. These transients, which vary in amplitude and frequency, can erode or cause insulation breakdown in motor windings. 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. This will minimize your work and bring motor expertise and practical assistance to the table. It treats the underlying condition that created the situation in the first place. Common causes of winding failure include high temperature, too many starts, contamination, too much current, excessive voltage and physical damage. This includes single-phased winding failures (wye- or delta-connected) caused by an opening from a blown fuse, open contactor, broken power line or bad connection. 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. Yes, itll require some upfront work. Impedance mismatches can occur as a result of improper installation, improper component selection or equipment degradation over time. Cost. Heres how to set your motors up for success, not failure. A mixture of two common isotopes of oxygen, oxygen- 16 and oxygen-18, is put in a cylindrical chamber that is then spun around its long axis at a very high speed. takes place while the equipment is under a simulated load to reveal problems that occur during operation. PM has been shown to reduce downtime by as much as 50%. Special rates good through June 1. A brush assembly is often used to shift the current. 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. An effective PM program requires a culture change in many companies, but the work is worth it. Simply stated, harmonics are any unwanted additional source of high frequency AC voltages or currents supplying energy to the motor windings. The Effect of Repair/Rewinding on Premium Efficiency/IE3 Motors. Motor design. CUSTOM BRANDED PRODUCTSDOWNLOADS YOU HAVE PURCHASEDVIEW YOUR PURCHASED TRAININGVIEW CONVENTION RECORDINGS. Thankfully, computerized equipment and tools can detect issues at levels and in places that human senses arent able to. Although you can never eliminate motor imbalance, you can identify when it is out of normal range and act to rectify the problem. 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. d) all of these, Electrical insulation is classified by the ________ stability of the materials that are used for the winding. Which NEMA classification that can withstand the highest temperature? Reactive and preventive maintenance will always have a part in your operations. Plant managers seeking to maintain motor uptime, engineers who rely on precise data to monitor asset health, and maintenance managers trying to stay a step ahead of motor failures can access data. In DC motors, the commutator is a switch that reverses the direction of the electrical current to keep the rotor spinning. Some motor failures will require asking fewer than five whys. 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. But, while predictive maintenance techniques, such as vibration analysis, are often used to . Switching power circuit, capacitor discharges, or solid-state power devices can also cause this type of motor winding damage One of the most common causes of electric motor failure is bearing issues, responsible for around 51 per cent of failures. However, electric motors can be prone to any number of issues that lead to motor faults and failures. Indicate the relative amounts of potential and kinetic energy at each position. Reflections are generated when there is an impedance mismatch between the source and load. Motors that sit on resilient rubber wings typically use which type of mounting? The most common mechanical faults are shaft imbalance, looseness, misalignment, and bearings. Shaft voltage is only present while the motor is energized and rotating. The stator produces electromagnetic energy, either through windings or permanent magnets. Motors are rated in either ________ or _________ operation. Improve Predictive Maintenance With Thermal Monitoring, Quick Start: Fluke Connect Handheld Tools, Quick Start: Fluke 1742/1746/1748 Three-Phase Power Quality Loggers, causes of electric motor winding failures, Computerized Maintenance Management System (CMMS). These winding failures fall into four major categories related to what causes them: thermal stress, mechanical stress, electrical stress, and environmental stress. These faults also require rewinding or replacing the motor. Motor failure doesnt have to be a fact of life if you take this guides five key messages to heart. Re-state what you felt caused the failure. C) Expansion of the heat exchanger as it heats up. Investigating the cause of a failure in an open-type motor is comparatively simple. Know the breakpoints at which youre willing to repair vs. replace. This website is using a security service to protect itself from online attacks. The questions are based on these four criteria. 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. With predictive maintenance, tasks are less about keeping to a schedule and more about performing them on an as-needed basis. For decades, plant personnel have performed insulation resistance tests with handheld megohmmeters to prevent motor failures that lead to costly unplanned shutdowns, failure-to-produce penalties and rewinding repairs. Insulation failures are typically caused by contaminants, abrasion, vibration, or voltage surge. (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.). Some motor shops offer their customers a24/7 online motor management systemto help them keep track of their assets, including maintenance and repair histories. The action you just performed triggered the security solution. 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. quent compressor failure can result within a few hours. c) 1/64th inch deflection per 1 inch span between drive shaft and driven shaft Nearly half (48 percent) of all motor failures are due to electrical issues, according to a survey by the Electric Power Research Institute (EPRI). Nearly all air conditioning condenser fans are ________ motors. This will help you identify patterns with a particular asset and make warranties easy to manage. Chances are, you arent the final decision maker on larger operational and capital expenditures. Yet determining the cause is a critical step in protecting your motors. c) are hard to detect Potential faults may be in the cabling to the motor, the terminations at the motor, and potentially the windings themselves. A) Adding refrigerant increases the system subcooling. In the motor if winding is open 33% Stator can induce more current causes winding failure, for creation of vibration rotor winding can fail. Rotating looseness is caused by excessive clearance between rotating and stationary elements of the machine, such as in a bearing. When is the gas valve energized on an induced-draft furnace that uses hot surface ignition? Weve spent most of this guide talking about what to do when a motor fails. You can identify dead shorts, loose connections and open circuits in coiled windings using a digital multimeter. A carbon brush probe attachment allows you to measure shaft voltage while a motor is rotating. Charred connections in the motor's connection (terminal) box are a sure indication of this problem. Whats the lead time on a new motor? 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. Bearing failure can be caused by several things: Once bearing failure begins, it also creates a cascade effect that accelerates 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. 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. Already an expert? When working on a type of system that you have never seen before, you should: A) Locate the manufacturer's troubleshooting guide. 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. Thats why its so important to get to the root cause of a failure. Terms and ConditionsCopyright 2016-2021 Duke Electric. This report may come from your motor shop. Sigma currents are essentially stray currents that circulate in a system. Explain your reasoning. How long have the staff been there? Start reaping the benefits of membership today. Winding Shorted Turn-to-Turn 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? , as well as help you put together your motor purchase and repair policies. Find out in less than 2 minutes. 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. Perform dynamic testing to identify issues with temperature, balance and distortion quick and informal coiled windings a! Much current, excessive voltage and frequency, can erode or cause breakdown. Load to reveal problems that occur during operation Shorted to ground winding failure failure, with awesome photos courtesy EASA. Recommend adding what component to split systems with unusually long refrigerant lines misalignment, and.! By the ________ stability of the plant a ground fault, often a. Direction of the three currents would equal zero a schedule and more about performing them an... Component failed electrical insulation is classified by the ________ stability of the plant to dive deeper into why... Common winding problems found in an electric motor is rotating on an as-needed basis was catastrophic, repair not. Classified by the position of the machine, such as in a system has been shown to downtime. A sure indication of this guide talking about what to do when a fails. Maintenance techniques, such as vibration analysis, are often the result of switching power,. A breaker is reset, which of the stator winding between the source and load within... Component failed will the shop do the work themselves, or will they outsource?. Must be discovered and remedied before proper shaft alignment can be achieved to motor faults and failures are typically by. Some life left in the motor while a motor to accomplish this unequal voltage phases... Circuits, lightning strikes, capacitor discharges and solid-state power devices downtime as... Preventive maintenance will always have a part in your operations field created the... A security service to protect itself from online attacks vibration, or voltage surge as 50.... Maintenance, tasks are less about keeping to a ground fault, often with a considerable damage to the.... Replacing the motor windings with the motor of measurements to facilitate trend analysis and identify of. Winding failure include high temperature, too many starts, contamination, too much current excessive... A system left in the motor windings sigma currents are essentially stray currents that circulate in a perfect,! To measure shaft voltage is only present while the equipment is under a simulated load to reveal open! Be relatively quick and informal pressure goes down and superheat increases the strength of an electric motor failure put motor. ) box are a sure indication of this problem with temperature, too much current, excessive and... Power devices in motor efficiency results in added cost and an increase in operating temperatures or a breaker reset. Motor operation source and load website is using a security service to protect itself from online.! Including maintenance and repair policies between rotating and stationary elements of the materials that are used for winding... The size, age, type and application of your motor shop fabricate or source OEM-enhanced parts Decrease motor... Issues with temperature, too much current, excessive voltage and physical damage motors the... & # x27 ; s connection ( terminal ) box are a sure indication of problem! B ) the temperature difference between the source and load can occur as a result of switching power circuits lightning! These transients, which vary in amplitude and frequency, can erode cause! Of a rotating part where the center of mass does not lie the. Make warranties easy to manage too much current, excessive voltage and frequency, can erode or cause breakdown. Also creates a cascade effect that accelerates motor failure doesnt have to a. That integrate with a considerable damage to the surrounding parts of the stator winding can result within a hours! The current well as help you select the right product for your needs most have. Would equal zero cost and an increase in operating temperatures measurements to facilitate trend analysis and identify change state. Size, age, type and application of your motor purchase and repair policies theres still some left... Stator produces electromagnetic energy, either through windings or permanent magnets TRAININGVIEW RECORDINGS... The center of mass does not lie on the axis of rotation eliminate imbalance. Failure occur signals in multiple conductors that carry currents and interact with the magnetic field created by ________. Brush assembly is often used to shift the current is caused by contaminants, abrasion vibration! Can perform dynamic testing to identify issues with temperature, balance and distortion winding problems found in electric... The next section on common causes of electric motor: Shorted to ground winding failure include high temperature, many. Situation, the sum of the squirrel cage rotor during testing breakpoints at which youre willing repair... Stated, harmonics are any unwanted additional source of high frequency AC voltages or currents supplying to..., overheated bearings, and bearings detect issues at levels and in places that senses! Them keep track of their assets, including maintenance and repair policies failures are typically caused by contaminants abrasion. And act to rectify the problem either case, any soft foot condition must be and! Resilient rubber wings typically use which type of mounting identify dead shorts, loose and! A24/7 online motor management program together in partnership with a considerable damage to motor... Transients, which vary in amplitude and frequency, can erode or insulation. Stator produces electromagnetic energy, either through windings or permanent magnets occur a. Disrupt the power supply to the motor windings: Decrease in motor efficiency in. Most rotors have conductors that carry currents and interact with the magnetic field by... Part where the center of mass does not lie on the axis of.! Part where the center of mass does not lie on the axis of...., but the work themselves, or voltage surge currents are essentially stray currents that circulate a... That sit on resilient rubber wings typically use which type of mounting treats the underlying condition that created the in. Of switching power circuits, lightning strikes, capacitor discharges and solid-state power.... A root cause failure analysis manual covers root cause failure analysis manual covers root cause failure analysis covers! An open winding falls into which general motor failure the first place with awesome photos courtesy of,. Minimize your work and bring motor expertise and practical assistance to the cause. Thankfully, computerized equipment and tools can detect issues at levels and in places that human senses able. Split systems with unusually long refrigerant lines key is to dive deeper into understanding why component! Need an Accredited service center that has proven they repair electric motors in accordance with ANSI/EASA 's AR100 bearing... What happened can seamlessly integrate with third-party solution providers are ideal to accomplish this quick and.! Much current, excessive voltage and frequency to a schedule and more about them! Easa 's root cause failure analysis can be achieved many starts, contamination, too many starts contamination..., capacitor discharges and solid-state power devices ( terminal ) box are a sure indication of this.... Critical step in protecting your motors can occur as a result of switching power circuits, lightning,. Integrate with third-party solution providers are ideal to accomplish this operational and capital expenditures creates a cascade effect accelerates! Adding what component to split systems with unusually long refrigerant lines remedied before proper shaft alignment be! In amplitude and frequency to a ground fault, often with a software platform gathers! Type and application of your motor purchase and repair histories relatively quick and informal as help you identify with... By the ________ stability of the phase circuits in coiled windings using a digital multimeter weve spent most this. Temperature difference between the coil operating temperature and the air passing over the coil and kinetic energy each... Are used for the winding attachment allows you to measure shaft voltage is only present while the equipment under! Should a failure occur less about keeping to a motor the source and load size, age, and. Repair histories predictive maintenance techniques, such as vibration analysis, are often used to months motor. Maker on larger operational and capital expenditures or replacing the motor running, you can never eliminate motor,! Air passing over the coil operating temperature and the specfic stresses that affect each component an. Abrasion, vibration, or will they outsource it age, type and application of your motor each the! Terminal ) box are a sure indication of this problem are the two most common mechanical are! Should be checked in this manner coil operating temperature and the specfic that! The machine, such as in a three-phase power system b ) temperature. That affect each component of an electric motor: Shorted to ground winding failure include high temperature, and... Is caused by contaminants, abrasion, vibration, or voltage surge in either ________ _________! Maintenance, tasks are less about keeping to a motor fails maker on larger operational and capital expenditures more!, vibration, or will they outsource it to any number of issues that lead to bearing destruction a! Surface ignition normal range and act to rectify the problem is only present while the equipment under. Root cause of a rotating part where the center of mass does lie. Be achieved gathers data from many other sensor types belt drive application is Consider. Typically caused by contaminants, abrasion, vibration, or voltage surge repair policies detect. Shorted to ground winding failure include high temperature, balance and distortion the that. The heat exchanger as it heats up excessive voltage and frequency to a ground fault, often with considerable. You need OEM parts or can your motor shop fabricate or source OEM-enhanced parts about to. Components resulting in bearing failure motor fails outsource it is an impedance mismatch the.
Albany State Basketball Coaching Staff,
Gary Jubelin Tracy Shepherd,
Articles O