EASA Motor Repair Slides

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Motor Management Truths

and Consequences:

Understanding Electric Motor

Rewinds and Efficiency

MDM Webcast May 25, 2011

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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

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MDM Sponsors

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)

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

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Motor Decisions Matter

SM

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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Tom Bishop, P.E.

Electrical Apparatus Service Association, Inc.

St. Louis, MO

Motor Management

Truths and Consequences: Understanding

Electric Motor Rewinds and Efficiency

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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

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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

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Rewind versus All Repairs

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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

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Mechanical Rebuilding

• Measurement of fits

• Bearing replacement

• Restore mechanical fits

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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

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Rewinding

• Resin treatment

and curing

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Effect of Repair and Rewind on

Efficiency

• Truths

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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

Using larger winding coil wire area

Reducing average length of turns

Average length of turn = (2 x L_s) + (4 x L_c)

Wire Size: AWG 16 Bare Diameter = .0508

Wire Size: AWG 17 Bare Diameter = .0453

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Truths

• Efficiency does not change with

subsequent rewinds

Core losses do not increase

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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

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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

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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…

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Consequences

• Reduction in efficiency

-- other factors

Winding copper (I2_R)

losses increased due to incorrect winding data or method

Bearing friction losses increased due to

incorrect bearings, fits, improper lubrication

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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

150hp 2 pole 95.9% 95.9% 0.0%

full to half slot lap 1st and 2nd rewinds Source: EASA/AEMT Motor Rewind Study, 2003

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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

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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

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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

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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

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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

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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



* Guidelines for Maintaining Motor Efficiency During Rebuilding

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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!

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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