MDM Webcast May 25, 2011 2 - 3 p.m. Eastern
Motor Management Truths and Consequences: Understanding Electric Motor Rewinds and Efficiency
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Today’s Web cast • MDM and motor management strategies • • • •
Overview of motor repair and rewinds Mechanical rebuilding and rewinding Effects of repair and rewind on efficiency Resources and considerations
• Questions and Answers 3
MDM Sponsors Efficiency Programs • Alliant Energy • BC Hydro • Efficiency Vermont • Long Island Power Authority (LIPA) • MidAmerican Energy Company • National Grid USA • New Jersey Office of Clean Energy • New York Power Authority (NYPA) • NYSERDA • Northwest Energy Efficiency Alliance • Pacific Gas & Electric (PG&E) • Southern California Edison (SCE) • Tennessee Valley Authority (TVA) • Xcel Energy
Manufacturers – Motor & Drive • ABB • Danfoss • GE Energy Motors • TECO-Westinghouse Motor Company Other Organizations • Advanced Energy • Copper Development Association, Inc. (CDA) • Electrical Apparatus Service Association (EASA)
For more information, visit: http://www.motorsmatter.org/sponsors/
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Motor Decisions MatterSM Managed by CEE, a national awareness campaign to:
• Encourage sound motor management, including – Demonstrate financial benefits of life cycle cost analysis – Inform motor repair-replace decisions – Promote premium efficiency motors and best practice motor repair
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Effective Motor Management
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Motor Management Truths and Consequences: Understanding Electric Motor Rewinds and Efficiency
Tom Bishop, P.E. Electrical Apparatus Service Association, Inc. St. Louis, MO
Background: What is EASA • Electrical Apparatus Service Association • Trade association serving the electrical and • • • •
mechanical apparatus sales, service and repair industry Founded in 1933 More than 1,900 member firm locations worldwide; approximately 1,400 in the U.S. Supports its members with industry research, engineering services, and education Establishes industry standards and practices 8
Motor Repair and Rewind Overview • All repairs include mechanical rebuilding Some repairs require rewinding
• Repair truths and consequences • Key resources • Key factors that influence the repair decision
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Rewind versus All Repairs
10 Source: A Survey of Faults ..., IEEE Petroleum and Chemical Industry Paper No. PCIC-94-01.
Mechanical Rebuilding • Consists of Test and inspect Disassemble Cleaning/overhaul Measurement of mechanical fits Bearing replacement Restore mechanical fits and components Assemble and test
• Most repairs are mechanical rebuilding without rewinding
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Mechanical Rebuilding • Test and inspect • Disassemble • Cleaning/overhaul
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Mechanical Rebuilding • Measurement of fits • Bearing replacement • Restore mechanical fits and components
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Mechanical Rebuilding • Assemble and test • Final step after mechanical repair with or without rewind
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Rewinding • A sub-process to mechanical rebuilding • Random (round wire) windings • Form coil windings
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Rewinding • Resin treatment and curing
• Electrical testing
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Effect of Repair and Rewind on Efficiency • Truths
• and Consequences
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Truths • Rewinding using best practices Maintains efficiency May improve efficiency
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Truths • Maintain efficiency by Copy-rewind or winding pattern improvement Using same winding coil wire area Using same average length of turns
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Truths • Opportunity to improve efficiency by
Wire Wire Size: Size:
AWG 17
Bare BareDiameter Diameter == .0453 .0453
Wire Size:
AWG 16
Bare Diameter = .0508
Using larger winding coil wire area Reducing average length of turns Average length of turn = (2 x Ls) + (4 x Lc) 20
Truths • Efficiency does not change with subsequent rewinds Core losses do not increase Winding data rarely changes
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Truths • Repairing can restore: Reduction in efficiency due to prior repairs • Restoration associated with a rewind • Restoration associated with mechanical repair
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Truths • Repairing can restore: Reduction in efficiency due to damage from motor failure(s) • Associated with winding failure(s) • Associated with mechanical failure(s)
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Truths • Repairing can restore: Motors to like-new condition Sometimes even better than new
• Repairs can enhance suitability of motor for its application and environment 24
Consequences • Consequences of poor practice repairs: Reduced efficiency Reduced reliability
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Consequences • Reduction in efficiency can occur Core damage due to winding removal Not the only reason for reduction in efficiency during repair… 26
Consequences • Reduction in efficiency -- other factors Winding copper losses increased due to incorrect winding data or method Bearing friction losses increased due to incorrect bearings, fits, improper lubrication (I2R)
Wire Size:
AWG 16
Bare Diameter = .0508
Wire Size:
AWG 17
Bare Diameter = .0453
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Consequences • Consequences of best practice repairs: Efficiency maintained • Efficiency may be improved Reliability maintained • Reliability may be improved Motor description
Efficiency before rewind
Efficiency after rewind
Efficiency change
Comments
7.5hp 4 pole
83.2%
84.0%
+0.8%
concentric to lap 5 burnouts 1 rewind
100hp 4 pole
93.0%
93.6%
+0.6%
full to half slot lap
100hp 4 pole
93.0%
93.7%
+0.7%
3rd rewind
0.0%
full to half slot lap 1st and 2nd rewinds
150hp 2 pole
95.9%
Source: EASA/AEMT Motor Rewind Study, 2003
95.9%
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Key Resource Documents • ANSI/EASA AR100 2010 Recommended Practice for the Repair of Rotating Electrical Apparatus
• EASA/AEMT Rewind Study The Effect of Repair/Rewinding on Motor Efficiency
• EASA Tech Note 16 Guidelines for Maintaining Motor Efficiency During Rebuilding 29
ANSI/EASA AR100 • The American National Standard for repair of rotating electrical apparatus • Purpose: establish guidelines in each step of electrical apparatus rewinding and rebuilding • Concisely (22 pages) describes best practice repairs 30
ANSI/EASA AR100 Benefits • Provides guidance for service centers to perform best practice repairs • End users are assured that compliant repairs follow a national standard
• Results: Quality repairs Reliable repairs Efficiency maintained
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ANSI/EASA AR100 Content • General Identification, inspection, condition assessment, failure analysis, cleaning, transport
• Mechanical repair Shafts, bearings, lubrication 14 fit and tolerance tables
• Rewinding Core inspection, winding removal, winding specification
• Testing Insulation resistance, high-potential, surge, core laminations, no-load
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EASA/AEMT Rewind Study Key content: Good Practice Guide
• Inspection and dismantling • Testing • Winding removal and rewind • Mechanical repairs • Reassembling
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EASA/AEMT Rewind Study Key content: Good Practice Guide
• Lessons learned Guide good practices AR100 best practices • Provides source details for good/best practices Repair reference document for service centers Specification reference document for end users 34
EASA Tech Note 16* Key content
• Do’s include Core test before and after winding removal Repair or replace defective laminations Evaluate impact on efficiency if winding design changes
• Don’ts include Overheat stator core/use open flame Short laminations when grinding/filing Increase winding resistance
* Guidelines for Maintaining Motor Efficiency During Rebuilding 35
Key factors in repair or rewind decision • Horsepower rating Economic evaluation
• Motor type/features Availability of new
• Maintenance history Evaluate reliability
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Questions?
Thank You! www.easa.com 37
Contact Information • Motor Decisions Matter Campaign – www.motorsmatter.org – Email:
[email protected] – Sign up for E-Newsletter
• MDM Events Calendar – www.motorsmatter.org/events/calendar.asp – Will include slides from today’s webcast
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