Your IP: A winding failurewhich is often caused by a breakdown of the windings insulationwill cause a short in the motor. Three-phase distribution systems often serve single-phase loads. The structured process of report writing gets you to think more and differently about what happened. 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. Capture and document critical measurements at installation, before and after maintenance and on a routine basis. Third, make your motor repair and replace decisions using an industry-accepted decision tree oronline decision toolto standardize and speed up your process. c) 1/64th inch deflection per 1 inch span between drive shaft and driven shaft In DC motors, the commutator is a switch that reverses the direction of the electrical current to keep the rotor spinning. 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. Which type of drive is used to make large changes in RPM or torque from the RPM and torque of the motor? The correct tension for any belt drive application is: A) Adding refrigerant increases the system subcooling. Check each wire, including T1, T2, T3 and the ground wire. Butdont screw it up. Excessive motor heat is a major cause of motor failure. When the winding is energized, it forms magnetic poles. 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. Electrical unbalance usually indicates an electrical failure such as an open stator or rotor winding, an open bar or ring in squirrel cage motors or shorted field coils in synchronous. Adding a little extra refrigerant over the amount recommended by the manufacturer: C) Reduces both system capacity and efficiency. Larger blower wheels are typically operated by ___________ motors. How efficient is the motor that failed? Impact: Decrease in motor efficiency results in added cost and an increase in operating temperatures. When replacing fuses be sure to match which of these ratings? This offline testing, often called static testing, looks at insulation resistance, wire damage and current leakage. Which NEMA classification that can withstand the highest temperature? 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. Connected tools and sensors offer all key stakeholders with access to the data they need. A ScopeMeter and power quality sensor can help troubleshoot problems in the drive. Weve come up with these. Its one thing to identify the component thats failed and another thing to isolate the cause of that component failure. Note:Under-voltage and over-voltage (exceedingNEMAstandards) will result in the same type of insulation deterioration. Motor windings account for about 32% of all AC electric motor repairs. The most common mechanical faults are shaft imbalance, looseness, misalignment, and bearings. Sigma currents are essentially stray currents that circulate in a system. However, electric motors can be prone to any number of issues that lead to motor faults and failures. What is the most likely cause of flames that are lifting off the burner? Skip to the next section on common causes of electric motor failure. |, free online repair or replace decision-making tool. Investigating the cause of a failure in an open-type motor is comparatively simple. Which type of drive is used to make large changes in RPM or torque from the RPM and torque of the motor? Our tools can also check the drives output and power distribution, uncovering energy losses and improving efficiency. 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. Terms and ConditionsCopyright 2016-2021 Duke Electric. 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. A) 240 volts. Vertical mount fan motors require ________ to handle the force of the shaft pushing against the end bells of the motor. 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. 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. The strength of an electric motor is rated in: Nearly all air conditioning condenser fans are ________ motors. Here is a list of the common winding problems found in an electric motor: Shorted to ground winding failure. In a motor drive circuit, the peak of the reflection could be as high as the DC bus voltage level. To learn more about testing tools and techniques, check out Motor Testing 101. Skip to the next section on. Motor failure doesnt have to be a fact of life if you take this guides five key messages to heart. A failed bearing has increased drag, emits more heat, and has lower efficiency because of a mechanical, lubrication, or wear problem. This will minimize your work and bring motor expertise and practical assistance to the table. Reproduction of these photographs by print or electronic means is prohibited. 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. This section is where you give the evidence for the cause of the failure. The failure mechanism involves the gradual development of a weakness in the insulation. If not, you might not get the most qualified team or best price. (If youve had small children in your life, youll also have flashbacks.) The motor and insulation tester assure safe operation, prolongs the life of electrical systems and motors. Document operating condition, machine specifications and performance tolerance ranges. 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. b. Fluke Accelix presents at FM Ireland 2018! 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); Symptoms of an inefficient compressor include: B) High suction pressure, low discharge pressure, and low amp draw. Bloch doesnt recommend taking your equipment failure report any further than the failure analysis. Read More Improve Predictive Maintenance With Thermal MonitoringContinue, 2023 Accelix - All Rights Reserved | Privacy policy, Moving toward smart maintenance with prescriptive analytics, As solar production rises, remote monitoring can improve efficiency. 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. Cloudflare Ray ID: 7a12d477b814c226 However, whether or not you can see the defective winding, an oil sample should always be taken for evaluation. But wouldnt it be better to avoid failure in the first place? Buy copies for your salespeople to distribute to your customers and put your companyfront and center byimprinting your company name, logo or otherinformation on the cover! In this case, different is better. 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. 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. Look on the outside of the motor for other potential problems, like holes or smoke points. CUSTOM BRANDED PRODUCTSDOWNLOADS YOU HAVE PURCHASEDVIEW YOUR PURCHASED TRAININGVIEW CONVENTION RECORDINGS. A root cause failure analysis can be relatively quick and informal. How many years of experience do they have? 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. The imagers test faulty connections, overheated bearings, and tank levels. Shaft failure is the least common cause of motor failure. Fox and McDonald's Introduction to Fluid Mechanics, Alan T. McDonald, John C Leylegian, John W Mitchell, Philip J. Pritchard, Rajesh Bhaskaran, Robert W Fox. Already an expert? An open winding falls into which general motor failure area? A) Setting the thermostat below room temperature. Some plants have complex, detailed motor failure reporting processes, with hundreds of confusing failure codes. 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. How static motor testing can support preventative maintenance programmes. Nearly half (48 percent) of all motor failures are due to electrical issues, according to a survey by the Electric Power Research Institute (EPRI). 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. 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. Which organizations specify standards for electric motors? 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. Looseness and bearing failures. 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. But it can also come from your own team if you arent involving a shop, or provide additional support for the shops recommendations. The stator is the stationary part of the motor. a) tight enough so that it does not slip on startup Contact us to speak with a specialist. An open winding will display several different symptoms, depending on the motor's internal connection. The ________ is used to identify all the controls in series with the load. Failures disrupt business operations, decrease productivity, and adversely impact a companys bottom line. The sigma currents are created as a result of the signal frequency, voltage level, capacitance and inductance in conductors. Others will need more than five. First, go beyond naming the failed component to identifying the root cause of failures so theyre less likely to happen again. Note:A one-percent voltage unbalance may result in a six- to ten-percent current unbalance. 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. Which NEMA classification can withstand the highest temperature? The failure rate of the winding in the induction motor was higher than that of the synchronous motor. Insulation failures are typically caused by contaminants, abrasion, vibration, or voltage surge. As part of a regular maintenance program, next-generation diagnostic and maintenance tools that include connected tools, sensors and software offer the best way to monitor an electric motors health. Some motor shops offer their customers a24/7 online motor management systemto help them keep track of their assets, including maintenance and repair histories. Impedance mismatches can occur as a result of improper installation, improper component selection or equipment degradation over time. Impact: Accelerated wear on rotating components resulting in bearing failure. In other words, the return current from the drive would be equal to the current to the drive. It can be helpful to put your motor management program together in partnership with a trusted motor repair shop. Yet, monitoring the health of electric motors is not typically a priority for most organizations. If the failure was catastrophic, repair may not be a good idea. PM has been shown to reduce downtime by as much as 50%. Winding Shorted Phase-to-Phase This type of insulation failure is typically caused by contaminants, abrasion, vibration or voltage surge. Whats the shops inventory of parts and materials for repairs? A megohmmeter can detect: Mark your calendars for FM Ireland and stop by Stand D10 to learn about the Accelix ecosystem of maintenance and reliability solutions. Motor overload occurs when a motor is under excessive load. 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). Winding Failures. 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. 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