Why motors fail


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Why motors fail

  1. 1. Motor Repair Guidelines <ul><li>Why do Motors Fail? </li></ul><ul><li>Repair vs. Replacement </li></ul><ul><li>Maintaining Reliability & Efficiency </li></ul>
  2. 2. Why do Motors Fail? <ul><li>Failed in service </li></ul><ul><li>Motor stored in preparation for service </li></ul><ul><li>Regularly scheduled maintenance </li></ul><ul><li>Predictive maintenance testing reveals potential concern regarding reliability </li></ul><ul><li>Motor requires upgrading </li></ul><ul><li>Modifications or addition of accessories for new process </li></ul><ul><li>Failed or damaged accessories, i.e. brakes, tachs, encoders, thermal devices </li></ul>
  3. 3. Why do Motors Fail? <ul><li>Motors don't fail just because of age or operating hours. Typical failures are caused by: </li></ul><ul><li>Heat </li></ul><ul><li>Power Supply Anomalies </li></ul><ul><li>Humidity </li></ul><ul><li>Contamination </li></ul><ul><li>Improper Lubrication </li></ul><ul><li>Unusual Mechanical Loads </li></ul>Motors have survived for several hundred thousand operating hours when these stresses have been minimized.
  4. 4. Common Causes For Motor Failures Failure distribution statistics, like these from IEEE Petro-Chemical Paper PCIC-94-01, are helpful, but still necessary to conduct a thorough root cause analysis when determining modes of failure.
  5. 5. Why do motors fail? <ul><li>Heat </li></ul><ul><li>Temperatures over the design rating take their toll in various ways. Electrical insulation deteriorates at a rate that may double for every 10 ºC. Excessive temperature also causes separation of greases and breakdowns of oils causing bearing failure. </li></ul><ul><li>Primary causes of overheating are: </li></ul><ul><li>Overloading </li></ul><ul><li>Too frequent starts (NEMA recommends two cold starts or one hot start per hour) </li></ul><ul><li>High ambient temperatures (NEMA typical design is 40 ºC) </li></ul><ul><li>Low or unbalanced voltages </li></ul><ul><li>High altitude operation </li></ul><ul><li>Inadequate ventilation i.e. damaged cooling fan, contaminated motor </li></ul>
  6. 6. Why do Motors Fail? <ul><li>Power Supply Anomalies </li></ul>Ideal power is a perfect sine wave on each phase at the motor's rated voltage & frequency-rarely achieved. The following problems appear. <ul><li>Harmonics : Cause overheating and decreased efficiency. </li></ul><ul><li>Overvoltage : At moderate levels is usually not damaging, but can reduce efficiency and power factor. (NEMA limit 110%) </li></ul><ul><li>Under-voltage : Increases current and causes overheating and reduced efficiency in fully loaded motors. It is relatively harmless in under-loaded motors. (NEMA limit 90% of rated). </li></ul><ul><li>Voltage unbalance : Causes overheating and reduced efficiency. Unbalance greater than 1% requires motor de-rating and motors should never be powered by a system with more than 5% unbalance. </li></ul>
  7. 7. Why do Motors Fail? <ul><li>Power Supply Anomalies </li></ul><ul><li>Voltage spikes : Commonly caused by capacitor switching, lightning, or cable stranding waves from a variable frequency drive (VFD). These tend to cause turn-to-turn failures. </li></ul><ul><li>Frequencies under 60 HZ from VFDs : The application should be reviewed to insure motor is suitable for the application without installation of supplemental cooling. </li></ul><ul><li>Bearing damage from shaft currents : This usually originates from VFDs. Consult the drive provider, motor manufacturer, or L&S Electric for information on strategies such as an insulated bearing sleeve, electro-conductive grease, or a shaft grounding system. </li></ul>
  8. 8. Why do Motors Fail? <ul><li>Humidity </li></ul><ul><li>Humidity becomes a problem when the motor is de-energized long enough to drop near the dew point temperature. </li></ul><ul><li>Moisture weakens the dielectric strength of electrical varnish and other insulating materials </li></ul><ul><li>Contributes to corrosion of bearings and other mechanical components </li></ul><ul><li>Moisture from the air can mix with certain particulate contaminants to create highly electro-conductive solutions. </li></ul><ul><li>Insulation moisture can be significantly reduced if the motor is kept warm. </li></ul>
  9. 9. Why do Motors Fail? <ul><li>Humidity Control Strategies: </li></ul><ul><li>By heating or dehumidification, keep the environment of unpowered motors below 80% relative humidity. </li></ul><ul><li>Specify new or rewound motors with heating elements for the windings and use these when the motor is unpowered. </li></ul><ul><li>Periodically rotate the shaft of stored motors to keep lubricant on the bearing surfaces. </li></ul>
  10. 10. Why do Motors Fail? <ul><li>Abrasion </li></ul><ul><li>Corrosion </li></ul><ul><li>Overheating </li></ul>Contamination Contamination cannot be completely excluded by total enclosure or even an explosion proof enclosure. Contamination destroys motors in three ways: Some airborne particulates are very abrasive. Motor coils flex when in use and contamination with abrasive particles eat away the wire enamel. Some substances, such as salt or coal dust are electrically conductive. Heavy accumulation of contaminants typically obstructs cooling passages.
  11. 11. Why do Motors Fail? <ul><li>Improper Lubrication </li></ul><ul><li>Unfortunately, there are more ways to get it wrong than right. One can over-lubricate as well as under-lubricate. </li></ul><ul><li>Grease itself introduces contaminants into bearings if careful control is not practiced. Mixing greases with different bases may cause grease constituents to separate and run out. </li></ul><ul><li>Different motors pose different requirements for the introduction of lubricant and removal of old lubricant. </li></ul><ul><li>Each individual application dictates the amount, type, and frequency of lubrication required. </li></ul><ul><li>This is a complete subject in itself. L&S Electric provides additional information for discussion. </li></ul>
  12. 12. Why do Motors Fail? <ul><li>Misaligned couplings </li></ul><ul><li>Over-tightened belt; or mis-alignment sheaves </li></ul><ul><li>Overly-compliant base or poor shimming of motor mounting feet </li></ul><ul><li>&quot;Soft Foot,&quot; (i.e. motor feet) not in the same plane </li></ul><ul><li>Dynamic imbalance of load or internal imbalance of motor rotor </li></ul><ul><li>Failure to bypass resonant speed point in VFD powered motors </li></ul><ul><li>Misapplication of bearings </li></ul>Unusual Mechanical Loads A variety of mechanical conditions can either overstress bearings, leading to early failure, or distort the motor frame causing asymmetric air gap, which in turn can cause vibration and bearing failure or winding overheating. Conditions to avoid are:
  13. 13. Repair vs. Replacement <ul><li>Difference in cost of repair vs. new purchase </li></ul><ul><li>Difference in efficiency of existing and proposed new motor </li></ul><ul><li>Availability of a new motor </li></ul><ul><li>Lifetime discounted cost of electric energy for each scenario </li></ul><ul><li>Possible mounting modifications </li></ul><ul><li>Cost in downtime and repairs from a possible early failure in either scenario </li></ul>Simple answer in principle. Rewind or otherwise repair a motor when cheaper than buying a new motor. Implementing this is a little more difficult because you need to consider the total cost of ownership. Ideally you have to consider:
  14. 14. Maintaining Reliability & Efficiency <ul><li>To help assure a quality repair, you should: </li></ul><ul><li>Evaluate prospective motor repair service providers </li></ul><ul><li>Don't pressure the provider for unrealistic turnaround time </li></ul><ul><li>Clearly communicate your requirements to the provider </li></ul>
  15. 15. Evaluate Repair Providers <ul><li>Look for indicators of a quality control program, such as evidence of participation in an ISO 9000 program, membership in EASA, & participation in EASA–Q program. </li></ul><ul><li>Inquire about staff morale, training, turnover, etc. </li></ul><ul><li>Determine whether the service center has sufficient facilities & materials to handle the size & type of motors you send them. </li></ul>Make an point to spend time evaluating each potential provider's service center.
  16. 16. <ul><li>Note what test equipment the service center owns and routinely uses to verify successful repair. Examples: </li></ul><ul><ul><li>Core loss tester </li></ul></ul><ul><ul><li>Surge comparison tester </li></ul></ul><ul><ul><li>Voltage regulated power supply for running at rated voltage </li></ul></ul><ul><ul><li>Vibration testing equipment </li></ul></ul><ul><li>Ask to see record-keeping system that the service center maintains for repaired motors </li></ul><ul><li>Inquire about method of insulation removal, burnoff, mechanical pulling, etc. </li></ul><ul><ul><li>For burn off, ask about methods for preventing flames or hotspots & ensuring uniform temperature when roasting multiple motors </li></ul></ul><ul><li>Take note of the overall cleanliness of the service center </li></ul>Evaluate Repair Providers
  17. 17. L&S Electric Provides <ul><li>Formal quality assurance program </li></ul><ul><li>Superior repair capabilities </li></ul><ul><li>Multiple repair service centers </li></ul><ul><li>Distribution of a wide variety of motors and electrical products </li></ul><ul><li>A diverse offering of products and services </li></ul>
  18. 18. Quality Management <ul><li>All operations certified to ISO 9001-2008 </li></ul><ul><li>Dedicated Quality Assurance Manager </li></ul><ul><li>Standards consistent at all facilities </li></ul><ul><li>Documented work procedures calibration program </li></ul>
  19. 19. Repair Warranty Rate
  20. 20. Minneapolis Service Center
  21. 21. Minneapolis Service Center <ul><li>2003 Established L&S Minneapolis Power Services Division in Ham Lake </li></ul><ul><li>2004 Acquired Antec Motor Service, Mounds View </li></ul><ul><li>2005 Acquired Advanced Motor Services, Minneapolis </li></ul><ul><li>2006 Service center expanded to nearly 55,000 square feet. Combined all three L&S Minneapolis locations in one centralized location </li></ul>
  22. 22. Minneapolis Service Center <ul><li>Motor Repair Productive Area: 35,000 sq. ft. </li></ul><ul><li>Power Services Productive Area: 2,560 sq. ft. </li></ul><ul><li>Warehouse: 6,000 sq. ft. </li></ul><ul><li>42' H Ceiling High Bay </li></ul>
  23. 23. Shop Capabilities <ul><li>Crane Capacity </li></ul><ul><ul><li>High Bay – 25 ton with 10 ton rider </li></ul></ul><ul><ul><li>High Bay/Low Bay work stations with 15 jib cranes – 16 foot - 2 ton cap </li></ul></ul><ul><ul><li>Middle Bay - 20 & 10 ton bridge cranes </li></ul></ul><ul><ul><li>East Bay - 15, 10, & 5 ton bridge cranes </li></ul></ul><ul><ul><li>West Bay - 15 & 10 ton bridge cranes </li></ul></ul>
  24. 24. Shop Capabilities <ul><li>Phenix High Voltage Test Panel </li></ul><ul><li>1500 KVA </li></ul><ul><li>0-13.8 KV AC </li></ul><ul><li>0-750 Volts DC </li></ul>
  25. 25. Shop Capabilities <ul><li>Large Burn off Oven: 120&quot; W × 192&quot; L × 162&quot; H </li></ul>
  26. 26. Shop Capabilities <ul><li>Large VPI System: 120&quot; Diameter, 120&quot; Deep, Von Roll 74035, Epoxy Varnish </li></ul>
  27. 27. Shop Capabilities <ul><li>Core Loss Tester </li></ul><ul><ul><li>25 kVA Lexeco; 10 kVA Lexeco </li></ul></ul><ul><li>Dynamic Balance Stands </li></ul><ul><ul><li>5,000 lb, 10,000 lb, & 25,000 lb. Capacity </li></ul></ul><ul><li>VPI System </li></ul><ul><ul><li>120&quot; Diameter × 120&quot; Deep w/ shaft well </li></ul></ul><ul><ul><li>Resin: Von Roll 74035 Epoxy </li></ul></ul><ul><li>Varnish Dip Tank </li></ul><ul><ul><li>52&quot; W × 48&quot; H × 48&quot; D. Resin: Von Roll 716C Polyester </li></ul></ul><ul><li>Epoxylite Trickle System: T wo-part epoxy resin </li></ul>
  28. 28. Shop Capabilities <ul><li>Lathes </li></ul><ul><ul><li>Monarch 60&quot; Swing, 212&quot; L // Monarch 18&quot; Swing, 60&quot; L </li></ul></ul><ul><ul><li>2- LeBlond 24&quot; Swing, 72&quot; L // LeBlond Gap Bed 18 -30&quot; Swing, 108&quot; </li></ul></ul><ul><li>Bridgeport Vertical Mill </li></ul><ul><li>Hydraulic Presses </li></ul><ul><ul><li>Horizontal - 600 ton, 72&quot; Swing, 204&quot; Length // Vertical – 100 ton </li></ul></ul><ul><li>Horizontal Pullers </li></ul><ul><ul><li>50 ton, 40&quot; reach // 50 ton, 38&quot; reach // 20 ton, 28&quot; reach </li></ul></ul><ul><li>Welders </li></ul><ul><ul><li>MIG, TIG, & Wire Feed // Steel & Aluminum </li></ul></ul><ul><li>Hot Metal Spray </li></ul><ul><ul><li>Eutectic Castolin – TeroDyne F4901 gun with Metco 452 powder </li></ul></ul>
  29. 29. Other Shop Equipment <ul><li>Paint Booth 16' W × 8&quot; D × 10' H </li></ul><ul><li>Stripping Booth </li></ul><ul><li>Steam Cleaning Booth 20' W × 18' D </li></ul><ul><li>Cryogenic (dry ice) Cleaning Machine </li></ul><ul><li>Fork Lifts </li></ul><ul><ul><li>(5) 8,000 lb. max capacity </li></ul></ul><ul><li>Fleet </li></ul><ul><ul><li>(2) Ford F550: 10,000 lb. capacity </li></ul></ul><ul><ul><li>Nissan UD: 13,000 lb. capacity </li></ul></ul><ul><ul><li>International F8100: 26,000 lb. capacity </li></ul></ul><ul><ul><li>Chevrolet 2500HD Pickup </li></ul></ul><ul><ul><li>Ford Ranger Pickup </li></ul></ul>
  30. 30. Motor & Generator Repair <ul><li>The Midwest's largest & most complete facilities </li></ul><ul><li>Capability to repair fractional through 10,000 HP </li></ul><ul><li>150 dedicated motor repair technicians </li></ul><ul><li>AC/DC, synchronous, & wound rotor </li></ul><ul><li>Field repair team </li></ul><ul><li>Rail equipment repair </li></ul><ul><li>Pump repair </li></ul><ul><li>Gearbox repair </li></ul><ul><li>Blower repair </li></ul><ul><li>UL ® -Approved for repairing explosion-proof motors </li></ul>
  31. 31. Corporate Repair Capability <ul><li>Complete calibration programs and documented work instructions at all locations </li></ul><ul><li>Capability to repair fractional through 15,000 HP </li></ul><ul><li>6 VPI systems </li></ul><ul><li>Redundant capability at all locations </li></ul><ul><ul><li>Winding, Machining, Balancing, & Testing </li></ul></ul>
  32. 32. Locations Duluth Menominee Sturtevant Minneapolis Appleton Wisconsin Rapids Montreal Wausau (3)
  33. 33. L&S Facilities <ul><li>Schofield, WI </li></ul><ul><li>Corporate headquarters </li></ul><ul><li>Large motor & generator repair </li></ul><ul><li>Locomotive equipment repair </li></ul><ul><li>Sturtevant, WI </li></ul><ul><li>Serving customers in Wisconsin, Illinois, and Indiana </li></ul><ul><li>Motor repair </li></ul><ul><li>Reliability services </li></ul><ul><li>Rothschild, WI </li></ul><ul><li>Motor repair </li></ul><ul><li>Central distribution warehouse </li></ul><ul><li>Reliability & Power Services </li></ul><ul><li>Appleton, WI </li></ul><ul><li>Serving customers in eastern WI </li></ul><ul><li>Motor repair </li></ul><ul><li>Power & Reliability Services </li></ul>
  34. 34. L&S Facilities <ul><li>Menominee, MI </li></ul><ul><li>Serving customers in northeast Wisconsin & eastern Upper Michigan </li></ul><ul><li>Motor repair through 3000 HP </li></ul><ul><li>New motor inventory through 200 HP </li></ul><ul><li>Duluth, MN </li></ul><ul><li>Serving customers in NW Wisconsin & Northern Minnesota </li></ul><ul><li>Motor inventory through 200 HP </li></ul><ul><li>Power & Reliability Services </li></ul><ul><li>Engineering </li></ul><ul><li>Engineered Systems </li></ul><ul><li>Hydroelectric automation </li></ul><ul><li>Steam Turbine automation </li></ul><ul><li>Panel manufacturing facility </li></ul>
  35. 35. Suppliers <ul><li>Marathon Electric </li></ul><ul><li>Baldor/Reliance Electric </li></ul><ul><li>Yaskawa </li></ul><ul><li>Emerson </li></ul><ul><li>Teco/Westinghouse </li></ul><ul><li>General Electric </li></ul><ul><li>Lafert </li></ul><ul><li>Cutler-Hammer </li></ul><ul><li>ABB </li></ul><ul><li>AEGIS </li></ul><ul><li>Grove Gear </li></ul><ul><li>Danaher </li></ul><ul><li>Overly Hautz </li></ul><ul><li>InPro Seal </li></ul><ul><li>Baumuller </li></ul>
  36. 36. Vendor Recognition <ul><li>Marathon Electric's Largest Distributor </li></ul><ul><li>Yaskawa's Electric's Largest NA Distributor </li></ul><ul><li>Baldor / Reliance's 5 Star & CSP Designation </li></ul><ul><li>General Electric flagship distributor </li></ul><ul><li>Lafert's Top 5 Distributor List </li></ul><ul><li>Over $20 million in annual motor sales </li></ul><ul><li>Start-up & warranty service for most major suppliers </li></ul>
  37. 37. Value We Offer <ul><li>Capabilities to service all types and sizes of electric motors, reducers, and pumps </li></ul><ul><li>A network of repair service centers </li></ul><ul><li>Ready access to sales & repair support </li></ul><ul><li>24/7/365 availability </li></ul><ul><li>Predictive and preventative services </li></ul><ul><li>ISO certified Quality Management System </li></ul><ul><li>Engineering & technical support </li></ul><ul><li>Free freight on our normal weekly routes </li></ul><ul><li>Warranty service for our suppliers </li></ul>
  38. 38. L&S Electric: we continually work hard to keep you running! Thank you for your attention.