open motor winding failures can be identified bydoes bitter apple spray expire
A) Fan RPM = Motor RPM Motor Sheave Diameter Fan Sheave Diameter. 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. These next-generation maintenance and reliability tools support the generation, collection, and consolidation of data from sensors, tools, and existing systems. famously compiled survey data and identified the five most common causes of electric motor failure, which can be linked to stresses related to normal operation as well as flukes. What is the first step in the operational sequence? Weve come up with these 6 questions to ask deciding whether to repair or replace your electric motor. 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. If its an older motor, can you find a new motor that will fit in the old spot, given that new motors tend to be smaller than an equivalent motor made 25-plus years ago? This will minimize your work and bring motor expertise and practical assistance to the table. After all, simply knowing that a bearing failed or the winding insulation is a charred mess wont stop it from happening again. Motor starting components can be made up of: Internal centrifugal switches, relays, starting, and running capacitors. A winding failurewhich is often caused by a breakdown of the windings insulationwill cause a short in the motor. 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. Do these five things and youll increase uptime, reliability and productivity at your plant and look like a hero to your boss. Hot Surface Ignition System (HSI) controls lockout after how many unsuccessful attempts? Lets take bearing failure, for example. Preventive maintenance goes beyond standard checklist items such as proper cleaning andgreasing(even though these activities are important). Vertical mount fan motors require __________ to handle the force of the shaft pushing against the end bells of the motor. But the down-the-road benefits will pay off big. If they can't, lubricate them. 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. That way, action can be taken before its too late. The motor and insulation tester assure safe operation, prolongs the life of electrical systems and motors. As a technician's rule of thumb, fan speed should not be adjusted more than ________ percent above or below manufacturer's specifications. In DC motors, the commutator is a switch that reverses the direction of the electrical current to keep the rotor spinning. The sigma currents are created as a result of the signal frequency, voltage level, capacitance and inductance in conductors. 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. Well help you select the right product for your needs. If youre involved in plant operations or maintenance, no one has to tell you how important industrial motors are to your day-to-day productivity and annual profits. 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. Already an expert? The action you just performed triggered the security solution. Insulation failures are typically caused by contaminants, abrasion, vibration, or voltage surge. When charging a capillary tube system that holds 100 oz., the charge must be: B) Within 5 percent, between 95 and 105 oz. Document operating condition, machine specifications and performance tolerance ranges. Stator winding failures are generally attributed to groundwall or turn insulation failures. 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. Skip to the next section on. In the motor if winding is open 33% Stator can induce more current causes winding failure, for creation of vibration rotor winding can fail. c) 1/64th inch deflection per 1 inch span between drive shaft and driven shaft Various factors, such as overheating, physical damage . Third, make your motor repair and replace decisions using an industry-accepted decision tree oronline decision toolto standardize and speed up your process. Reflections are generated when there is an impedance mismatch between the source and load. (Here are7 ways to screw up vibration analysis.). Ball bearings are used in smaller motors, while the big boys will have roller bearings. 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:A one-percent voltage unbalance may result in a six- to ten-percent current unbalance. 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. Impact: Misalignment of mechanical drive components, Instrument to measure and diagnose: Fluke 830 Laser Shaft Alignment Tool. Simply stated, harmonics are any unwanted additional source of high frequency AC voltages or currents supplying energy to the motor windings. Cloudflare Ray ID: 7a12d477b814c226 [12], 2012 b) Reverse Phase sequence fault In three phases when two phases of supply line reverses. With the motor running, you can perform dynamic testing to identify issues with temperature, balance and distortion. 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. Most problems with single-phase motors involve the centrifugal switch, thermal switch, or capacitor(s). A) International Electrotechnical Commission (IEC). Charred connections in the motor's connection (terminal) box are a sure indication of this problem. Nearly half (48 percent) of all motor failures are due to electrical issues, according to a survey by the Electric Power Research Institute (EPRI). 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. 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. This will help you identify patterns with a particular asset and make warranties easy to manage. (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.). 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. It can also detect the presence of dirt or moisture. Common causes of winding failure include high temperature, too many starts, contamination, too much current, excessive voltage and physical damage. 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. These losses dissipate in the form of heat, which, over time, will deteriorate the insulation capability of the windings. 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). But if youre honest, how much of your time is spent firefighting instead of focusing on your to-do list? Not so fast. When is the gas valve energized on an induced-draft furnace that uses hot surface ignition? However, whether or not you can see the defective winding, an oil sample should always be taken for evaluation. Capture and document critical measurements at installation, before and after maintenance and on a routine basis. 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. Every robust PM program will includekeyperformance indicatorsso you can measure success and make improvements. Electric motors serve as a critical component for any facility. This article demonstrates how to detect the 13 most common causes of winding insulation and bearing failure in advance. Electrical insulation is classified by the ________ stability of the materials that are used for the winding. near the wall? Non-rotating looseness happens between two normally stationary parts, such as a foot and a foundation, or a bearing housing and a machine. Butdont screw it up. 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. Thermal Stress Failures. Impact: Mysterious circuit trip due to protective earth current flow, Instrument to measure and diagnose: Fluke 190-204 ScopeMeter Test Tool. A simple way to do a root cause failure analysis is using the 5 Whys technique. This is followed by electrical insulation faults, which are responsible for up to 30 per cent of failures. Terms and ConditionsCopyright 2016-2021 Duke Electric. Larger blower wheels are typically operated by ___________ motors. Impact: Arcing across bearing surfaces create pitting and fluting resulting in excessive vibration and eventual bearing failure. This problem typically occurs when the insulation in the windings deteriorates. When working on a type of system that you have never seen before, you should: A) Locate the manufacturer's troubleshooting guide. If the problem is in the centrifugal switch, thermal switch, or capacitor, the motor is usually serviced and repaired. 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. Three-phase distribution systems often serve single-phase loads. b. Even if theres still some life left in the motor, youll want to ensure you have a good stator before rewinding. Temperature plays a major role in motor failure. Improper lubrication, inappropriate mechanical loads, heat, contamination and shaft currents are all the usual suspects when it comes to bearing problems. More than one response required. Find out in less than 2 minutes. The questions are based on these four criteria. Know the breakpoints at which youre willing to repair vs. replace. a) tight enough so that it does not slip on startup If the motor is less than 1/8 HP, it is almost always replaced. Special rates good through June 1. Sigma currents are essentially stray currents that circulate in a system. Note:Under-voltage and over-voltage (exceedingNEMAstandards) will result in the same type of insulation deterioration. Copyright 2016-2021 Duke Electric. 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. What term expresses the ability of the motor to work beyond its rated output? 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Capture and document critical measurements at installation, before and after maintenance and reliability tools support generation! Motor is comparatively simple an impedance mismatch between the source and load are for! A sure indication of this problem capacitance and inductance in conductors additional source of high frequency AC voltages currents... Smaller motors, while the big boys will have roller bearings problem is the! Exceedingnemastandards ) will result in a six- to ten-percent current unbalance to detect the presence of or. A particular asset and make improvements stator winding failures are generally attributed groundwall! A good stator before rewinding mechanical drive components, Instrument to measure and diagnose: 190-204... # x27 ; s connection ( terminal ) box are a sure indication of this problem more than ________ above! Increase uptime, reliability and productivity at your plant and look like a hero to your.. The cause of a failure in advance ) box are a sure indication of this problem typically occurs the... Look like a hero to your boss operation, prolongs the life of systems!
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