This article demonstrates how to detect the 13 most common causes of winding insulation and bearing failure in advance. Start by completely disconnecting the spindle motor from all power sources. b) the minimum tension required to keep the belt from slipping at its maximum torque When there is high resistance across the contacts when they are closed: C) A voltage drop will be read across the contacts. 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) International Electrotechnical Commission (IEC). Temperature plays a major role in motor failure. Manufacturers often recommend adding what component to split systems with unusually long refrigerant lines? e) all of these, When measuring the leads of a multispeed shaded pole motor, there should be measurable resistance between all the leads. Identify causes you eliminated and why. Whos got time to write a motor failure report? b) insulation faults 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. (Here are7 ways to screw up vibration analysis.). Sigma current can be found in the motor cabling and is the sum of the current of the three phases at any one point in time. Impedance mismatches can occur as a result of improper installation, improper component selection or equipment degradation over time. If the failure was catastrophic, repair may not be a good idea. Heres an example of the 5 Whys in action. This additional energy is not used to turn the motor shaft but circulates in the windings and ultimately contributes to internal energy losses. This device checks motor speed, torque, power and efficiency, and also checks for motor insulation degradation. A quality laser alignment tool can typically determine whether there is a soft foot problem on a rotating machine. Instrument to measure and diagnose: Fluke 810 Vibration Tester. In DC motors, the commutator is a switch that reverses the direction of the electrical current to keep the rotor spinning. Some motor shops offer their customers a24/7 online motor management systemto help them keep track of their assets, including maintenance and repair histories. Yet determining the cause is a critical step in protecting your motors. An open winding will display several different symptoms, depending on the motor's internal connection. 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. It can also detect the presence of dirt or moisture. In other words, the return current from the drive would be equal to the current to the drive. The expected temperature drop through a direct expansion evaporator coil: D) Can be determined with a chart supplied by the coil manufacturer. Which organizations specify standards for electric motors? 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. Re-state what you felt caused the failure. This is the logical outcome, given what youve written in the rest of the report. Polarization index (PI) testing takes a ratio of the winding insulation resistance after 1 minute and 10 minutes to tell you how well the motor is functioning. This is another biggie. A megohmmeter can detect: Reactive and preventive maintenance will always have a part in your operations. 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. Maintenance software and data gathering devices that integrate with third-party solution providers are ideal to accomplish this. Know the breakpoints at which youre willing to repair vs. replace. Thats why its so important to get to the root cause of a failure. A single-phased winding failure is the result of an open in one phase of the power supply to the motor. The benefits of detecting, identifying, and evaluating electric motor abnormalities are decreased motor failures and less unexpected downtime. You can identify early signs of motor trouble by performing ongoing monitoring of motor health. Here are some of the more common motor tests to perform regularly as part of your early warning system. 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. PM has been shown to reduce downtime by as much as 50%. 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. 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. To keep operations running smoothly, implementing preventive maintenance programs leads to a predictive and prescriptive maintenance future. 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? 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. If the motor is less than 1/8 HP, it is almost always replaced. 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. Many plants are taking preventive maintenance a step further using condition monitoring and other tools to look for signs of future motor failure. Always ensure the motor thermal protector has not opened. The correct tension for any belt drive application is: 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. By continually asking why, youll get a deeper understanding of what happened. Potential faults may be in the cabling to the motor, the terminations at the motor, and potentially the windings themselves. Electronic controls on air-conditioning systems typically report faults by: The most common cause of airflow-related problems in air-conditioning units is: If an air-conditioning system is operating with an 80F return air temperature and a 50F supply air temperature: 11). That way, action can be taken before its too late. This will help you identify patterns with a particular asset and make warranties easy to manage. 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. 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. takes place while the equipment is under a simulated load to reveal problems that occur during operation. Are the techs CSA-certified? Then we identify the 5 common causes of industrial motor failure. The best way to diagnose an ECM motor is to: Turn off power to the unit, remove the control harness, and connect a test controller. to ask deciding whether to repair or replace your electric 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. Weve spent most of this guide talking about what to do when a motor fails. 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\. Should we repair the motor or replace it? The open is usually caused by a blown fuse, an open contactor, a broken power line or bad connections. Choose the more stable alkene in each of the following pairs. This weakness is . 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. In the motor if winding is open 33% Stator can induce more current causes winding failure, for creation of vibration rotor winding can fail. Voltage surges are often the result of switching power circuits, lightning strikes, capacitor discharges and solid-state power devices. Oil analysis can be used to check on sleeve bearings that have oil reservoirs. What is the effect on suction pressure and superheat? Most rotors have conductors that carry currents and interact with the magnetic field created by the stator. It may also occur as a result of excessive starts or reversals. The majority of problems with residential air-conditioning systems are due to: How does the refrigerant charge affect a system's subcooling? Motors are rated in either ________ or _________ operation. Thermal deterioration of insulation in one phase of the stator winding. 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. runs a motor through its paces while its turned off. How long will it take to get the motor repaired? How is the subcooling of an air-conditioning system affected by a low refrigerant charge? 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). Once acid is identified in Bearings - 51% Windings - 16% External causes -16% Unknown - 10% Rotor - 5% Shaft or coupling - 2% Repair or replace? 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. They can test correct shaft alignment, imbalances, looseness, misalignment, and bearings. Others will need more than five. Whats the lead time on a new motor? Chances are, you arent the final decision maker on larger operational and capital expenditures. Soft foot refers to a condition in which the mounting feet of a motor or driven component are not even, or the mounting surface upon which the mounting feet sit is not even. 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? Impact: Misalignment of mechanical drive components, Instrument to measure and diagnose: Fluke 830 Laser Shaft Alignment Tool. What causes the little pops and ticking that can be heard in some furnaces before the blower comes on? c) 1/64th inch deflection per 1 inch span between drive shaft and driven shaft With the motor running, you can perform dynamic testing to identify issues with temperature, balance and distortion. What is their internal quality management system and how do they make sure theyre following it? A simple way to do a root cause failure analysis is using the 5 Whys technique. Angular soft footangular soft foot occurs when one of the mounting feet is not parallel or normal to the mounting surface. Maintenance teams can cost-effectively implement this technology platform to address their needs with ease. Hopscotching is an electrical troubleshooting technique that works by: A) Starting at a point where voltage exists and moving one lead at a time from point to point toward the non-functioning load until voltage is lost. In fact, Cooper Bussmann says old age causes only 10% of electric motor failures. Preventive maintenance goes beyond standard checklist items such as proper cleaning andgreasing(even though these activities are important). A failed bearing has increased drag, emits more heat, and has lower efficiency because of a mechanical, lubrication, or wear problem. Most insulation failures ultimately lead to a ground fault, often with a considerable damage to the surrounding parts of the motor. Abnormally low resistance in the electric motor can be a sign of shorted to ground winding failure. Look for a clear, comprehensive, standardized reporting process, including rigorous visual and written documentation. When motor shaft voltages exceed the insulating capability of the bearing grease, flashover currents to the outer bearing will occur, thereby causing pitting and grooving to the bearing races. Shaft voltage is only present while the motor is energized and rotating. 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. It may also occur as a result of excessive starts or reversals. If there is no resistance or the resistance is uneven, the motor is likely faulty. Motor winding damage Motor winding damage (all windings) is caused by the thermal deterioration of the insulation in all phases, which is caused by motor overload or over/under voltage situations. When an electric motor fails, theres one question that must be answered. Weve put together these 7 questions to ask your electric motor repair shop. Note:Under-voltage and over-voltage (exceedingNEMAstandards) will result in the same type of insulation deterioration. Bloch doesnt recommend taking your equipment failure report any further than the failure analysis. Why. Some plants have complex, detailed motor failure reporting processes, with hundreds of confusing failure codes. Once the underlying causes are identified and understood, implementing preventive maintenance procedures through diagnostics testing is the best way to help remedy electric motor winding failures. Click to reveal The questions are based on these four criteria. How static motor testing can support preventative maintenance programmes. 195.201.81.185 This offline testing, often called static testing, looks at insulation resistance, wire damage and current leakage. 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); Grounded windings can be detected by measuring the resistance with a multimeter between: Fundamentals of Engineering Economic Analysis, David Besanko, Mark Shanley, Scott Schaefer, Introduction to Chemical Engineering Thermodynamics, Hendrick Van Ness, J.M. These values could be affected by the position of the squirrel cage rotor during testing. and preventive maintenance (PM). This is another biggie. 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. Weve hinted at the need to take a systematic, big-picture approach to your electric motors, but heres where we stop beating around the bush: if you want to prevent motor failure, put a total motor management program in place at your plant. 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). 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