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Motor Repair Guidelines Why do Motors Fail? Repair vs. Replacement Maintaining Reliability & Efficiency
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Why motors fail

Jan 19, 2015

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Page 1: Why motors fail

Motor Repair Guidelines

Why do Motors Fail?

Repair vs. Replacement

Maintaining Reliability & Efficiency

Page 2: Why motors fail

Why do Motors Fail? Failed in service Motor stored in preparation for service Regularly scheduled maintenance Predictive maintenance testing reveals potential

concern regarding reliability Motor requires upgrading Modifications or addition of accessories

for new process Failed or damaged accessories, i.e. brakes, tachs,

encoders, thermal devices

Page 3: Why motors fail

Why do Motors Fail?

Motors don't fail just because of age or operating hours. Typical failures are caused by:

HeatPower Supply AnomaliesHumidityContaminationImproper LubricationUnusual Mechanical Loads

Motors have survived for several hundred thousand operating hours when these stresses have been minimized.

Page 4: Why motors fail

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.

Page 5: Why motors fail

Why do motors fail?Heat Temperatures over the design rating take their toll in various ways. Electrical insulation deteriorates at a rate that may double for every10 ºC. Excessive temperature also causes separation of greases and breakdowns of oils causing bearing failure.

Primary causes of overheating are: Overloading Too frequent starts (NEMA recommends two cold starts or one hot start per hour) High ambient temperatures (NEMA typical design is 40 ºC) Low or unbalanced voltages High altitude operation Inadequate ventilation i.e. damaged cooling fan, contaminated motor

Page 6: Why motors fail

Why do Motors Fail?Power Supply Anomalies

Ideal power is a perfect sine wave on each phase at the motor's rated voltage & frequency-rarely achieved. The following problems appear.

Harmonics: Cause overheating and decreased efficiency.

Overvoltage: At moderate levels is usually not damaging, but can reduce efficiency and power factor. (NEMA limit 110%)

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).

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.

Page 7: Why motors fail

Why do Motors Fail?Power Supply Anomalies 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.

Frequencies under 60 HZ from VFDs: The application should be reviewed to insure motor is suitable for the application without installation of supplemental cooling.

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.

Page 8: Why motors fail

Why do Motors Fail?Humidity

Humidity becomes a problem when the motor is de-energized long enough to drop near the dew point temperature. Moisture weakens the dielectric strength of electrical

varnish and other insulating materials Contributes to corrosion of bearings and other

mechanical components Moisture from the air can mix with certain

particulate contaminants to create highly electro-conductive solutions.

Insulation moisture can be significantly reduced if the motor is kept warm.

Page 9: Why motors fail

Why do Motors Fail?

Humidity Control Strategies: By heating or dehumidification, keep the environment of

unpowered motors below 80% relative humidity. Specify new or rewound motors with heating elements

for the windings and use these when the motor is unpowered.

Periodically rotate the shaft of stored motors to keep lubricant on the bearing surfaces.

Page 10: Why motors fail

Why do Motors Fail?

Abrasion Corrosion Overheating

ContaminationContamination 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.

Page 11: Why motors fail

Why do Motors Fail?Improper LubricationUnfortunately, there are more ways to get it wrong than right. One can over-lubricate as well as under-lubricate. 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. Different motors pose different requirements for the introduction of lubricant and removal of old lubricant. Each individual application dictates the amount, type, and frequency of lubrication required.

This is a complete subject in itself. L&S Electric provides additional information for discussion.

Page 12: Why motors fail

Why do Motors Fail?

Misaligned couplings Over-tightened belt; or mis-alignment sheaves Overly-compliant base or poor shimming of motor mounting feet "Soft Foot," (i.e. motor feet) not in the same plane Dynamic imbalance of load or internal imbalance of motor rotor Failure to bypass resonant speed point in

VFD powered motors Misapplication of bearings

Unusual Mechanical LoadsA 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:

Page 13: Why motors fail

Repair vs. Replacement

Difference in cost of repair vs. new purchase Difference in efficiency of existing and proposed new motor Availability of a new motor Lifetime discounted cost of electric energy for each scenario Possible mounting modifications Cost in downtime and repairs from a possible

early failure in either scenario

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:

Page 14: Why motors fail

Maintaining Reliability & EfficiencyTo help assure a quality repair, you should:

Evaluate prospective motor repair service providers

Don't pressure the provider for unrealistic turnaround time

Clearly communicate your requirements to the provider

Page 15: Why motors fail

Evaluate Repair Providers

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.

Inquire about staff morale, training, turnover, etc. Determine whether the service center has sufficient facilities &

materials to handle the size & type of motors you send them.

Make an point to spend time evaluating each potential provider's service center.

Page 16: Why motors fail

Note what test equipment the service center owns and routinely uses to verify successful repair. Examples:• Core loss tester• Surge comparison tester• Voltage regulated power supply for

running at rated voltage• Vibration testing equipment

Ask to see record-keeping system that the service center maintains for repaired motors

Inquire about method of insulation removal, burnoff, mechanical pulling, etc.

• For burn off, ask about methods for preventing flames or hotspots & ensuring uniform temperature when roasting multiple motors

Take note of the overall cleanliness of the service center

Evaluate Repair Providers

Page 17: Why motors fail

L&S Electric Provides Formal quality assurance program Superior repair capabilities Multiple repair service centers Distribution of a wide variety of motors and electrical products A diverse offering of products and services

Page 18: Why motors fail

Quality Management

All operations certified to ISO 9001-2008 Dedicated Quality Assurance Manager Standards consistent at all facilities Documented work procedures calibration program

Page 19: Why motors fail

Repair Warranty Rate

Page 20: Why motors fail

Minneapolis Service Center

Page 21: Why motors fail

Minneapolis Service Center

2003 Established L&S Minneapolis Power Services Division in Ham Lake

2004 Acquired Antec Motor Service, Mounds View 2005 Acquired Advanced Motor Services, Minneapolis 2006 Service center expanded to nearly 55,000 square

feet. Combined all three L&S Minneapolis locations in one centralized location

Page 22: Why motors fail

Minneapolis Service Center Motor Repair Productive Area: 35,000 sq. ft. Power Services Productive Area: 2,560 sq. ft. Warehouse: 6,000 sq. ft. 42' H Ceiling High Bay

Page 23: Why motors fail

Shop Capabilities Crane Capacity

• High Bay – 25 ton with 10 ton rider• High Bay/Low Bay work stations with

15 jib cranes – 16 foot - 2 ton cap• Middle Bay - 20 & 10 ton bridge cranes• East Bay - 15, 10, & 5 ton bridge cranes• West Bay - 15 & 10 ton bridge cranes

Page 24: Why motors fail

Shop CapabilitiesPhenix High Voltage Test Panel 1500 KVA 0-13.8 KV AC 0-750 Volts DC

Page 25: Why motors fail

Shop Capabilities Large Burn off Oven: 120" W × 192" L × 162" H

Page 26: Why motors fail

Shop Capabilities Large VPI System: 120" Diameter, 120" Deep,

Von Roll 74035, Epoxy Varnish

Page 27: Why motors fail

Shop Capabilities Core Loss Tester

• 25 kVA Lexeco; 10 kVA Lexeco Dynamic Balance Stands

• 5,000 lb, 10,000 lb, & 25,000 lb. Capacity VPI System

• 120" Diameter × 120" Deep w/ shaft well• Resin: Von Roll 74035 Epoxy

Varnish Dip Tank• 52" W × 48" H × 48" D. Resin: Von Roll 716C Polyester

Epoxylite Trickle System: Two-part epoxy resin

Page 28: Why motors fail

Shop Capabilities Lathes

• Monarch 60" Swing, 212" L // Monarch 18" Swing, 60" L• 2- LeBlond 24" Swing, 72" L // LeBlond Gap Bed 18 -30" Swing, 108"

Bridgeport Vertical Mill Hydraulic Presses

• Horizontal - 600 ton, 72" Swing, 204" Length // Vertical – 100 ton

Horizontal Pullers• 50 ton, 40" reach // 50 ton, 38" reach // 20 ton, 28" reach

Welders• MIG, TIG, & Wire Feed // Steel & Aluminum

Hot Metal Spray• Eutectic Castolin – TeroDyne F4901 gun with Metco 452 powder

Page 29: Why motors fail

Other Shop Equipment Paint Booth 16' W × 8" D × 10' H Stripping Booth Steam Cleaning Booth 20' W × 18' D Cryogenic (dry ice) Cleaning Machine Fork Lifts

• (5) 8,000 lb. max capacity Fleet

• (2) Ford F550: 10,000 lb. capacity• Nissan UD: 13,000 lb. capacity• International F8100: 26,000 lb. capacity• Chevrolet 2500HD Pickup• Ford Ranger Pickup

Page 30: Why motors fail

Motor & Generator Repair The Midwest's largest & most complete facilities Capability to repair fractional through 10,000 HP 150 dedicated motor repair technicians AC/DC, synchronous,

& wound rotor Field repair team Rail equipment repair Pump repair Gearbox repair Blower repair UL®-Approved for repairing

explosion-proof motors

Page 31: Why motors fail

Corporate Repair Capability

Complete calibration programs and documented work instructions at all locations

Capability to repair fractional through 15,000 HP 6 VPI systems Redundant capability at all locations

• Winding, Machining, Balancing, & Testing

Page 32: Why motors fail

Locations

Duluth

Menominee

Sturtevant

Minneapolis

AppletonWisconsin Rapids

Montreal

Wausau (3)

Page 33: Why motors fail

L&S Facilities

Schofield, WI Corporate headquarters Large motor & generator repair Locomotive equipment repair

Sturtevant, WI Serving customers in Wisconsin,

Illinois, and Indiana Motor repair Reliability services

Rothschild, WI Motor repair Central distribution warehouse Reliability & Power Services

Appleton, WI Serving customers in eastern WI Motor repair Power & Reliability Services

Page 34: Why motors fail

L&S Facilities

Menominee, MI Serving customers in northeast

Wisconsin & eastern Upper Michigan Motor repair through 3000 HP New motor inventory through 200 HP

Duluth, MN Serving customers in NW Wisconsin &

Northern Minnesota Motor inventory through 200 HP Power & Reliability

Services

Engineering Engineered Systems Hydroelectric automation Steam Turbine automation Panel manufacturing facility

Page 35: Why motors fail

Suppliers Marathon Electric Baldor/Reliance Electric Yaskawa Emerson Teco/Westinghouse General Electric Lafert Cutler-Hammer

ABB AEGIS Grove Gear Danaher Overly Hautz InPro Seal Baumuller

Page 36: Why motors fail

Vendor Recognition Marathon Electric's Largest Distributor Yaskawa's Electric's Largest NA Distributor Baldor / Reliance's 5 Star & CSP Designation General Electric flagship distributor Lafert's Top 5 Distributor List Over $20 million in annual motor sales Start-up & warranty service for most major suppliers

Page 37: Why motors fail

Value We Offer Capabilities to service all types and sizes of electric

motors, reducers, and pumps A network of repair service centers Ready access to sales & repair support 24/7/365 availability Predictive and preventative services ISO certified Quality Management System Engineering & technical support Free freight on our normal weekly routes Warranty service for our suppliers

Page 38: Why motors fail

L&S Electric: we continually work hard to keep you running!

Thank you for your attention.