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SHORT COURSE

MOTOR CURRENT SIGNATURE ANALYSIS

FOR

DIAGNOSIS OF FAULTS IN INDUCTION MOTOR DRIVES

Prof Bill Thomson

Director and Consultant

EM Diagnostics Ltd

EM Diagnostics Ltd 20 Greystone Road, Alford, Aberdeenshire, AB33 8TY, Scotland, UK

Tel : +44 (0) 19755 62446 Fax : +44 (0) 19755 62628

e-mail : [email protected] web site : www.mcsainterpreter.com

William T. Thomson EM Diagnostics Ltd 2001 - unauthorised copying, reproduction or amendment of all or part prohibited.
mailto:[email protected]://www.mcsainterpreter.com/http://www.mcsainterpreter.com/mailto:[email protected]


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MCSA : MOTOR CURRENT SIGNATURE ANALYSIS

INDUCTION MOTOR DRIVES

DIAGNOSE PROBLEMS PRIOR TO MOTORDRIVE FAILURE

BROKEN ROTOR BARS ABNORMAL AIRGAP ECCENTRICITY

SHORTED TURNS IN LV STATORS

ABNORMAL ROTOR DYNAMICS

PUMP WEAR MISALIGNMENT

William T. Thomson EM Diagnostics Ltd 2001 - unauthorised copying, reproduction or

amendment of all or part prohibited


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INDUCTION MOTOR DRIVE SYSTEMS

WHY SO IMPORTANT?

USA 800,000 MW GENERATING CAPACITY

40-50% CONSUMED BY INDUCTION MOTORS

320,000MW PLANT SYSTEMS

328 MILLION HORSEPOWER


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Power

Utilities

Oil & Gas

Chemical

Refineries

Pulp &

Paper

Mining

Shipping

MOD

Transport

Nuclear

WindPower

DuPont

Kodak

Ford

Uptime of

Induction Motor

Drive Systems


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8 CW Induction

Motor Drives

8 PA Induction

Motor Drives8 ID Induction

Motor Drives

26 Mill Motors

Induction Motor

Drives

8Coal Conveyor

Induction Motor

Drives

8 FD Induction

Motor Drives

8 Compressor

Induction Motor

Drives

Numerous

other

InductionMotor Drives

2000 MW Coal

Fired

Power Station


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3 PHASE, SCIM, 6.6kV,

2800kW/3753H.P., 2-POLE,

3570r.p.m., 60Hz,

(Full-load slip = 0.00833 or

0.833%)

William T. Thomson EM Diagnostics Ltd 2001 - unauthorisedcopying, reproduction or amendment of all or part prohibited


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MOTOR CURRENT SIGNATURE ANALYSIS

CONDITION MONITORING TECHNIQUE

INSURANCE POLICY

TO PREVENT FAILURES

REDUCE DOWNTIME AND REPAIR COSTS

PREVENT LOST PRODUCTION

INCREASE RELIABILITY - PRODUCT DELIVERY


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MCSA

MCSA : On-Line Monitoring and Analysis of Current to Assess

the Condition of an Induction Motor Drive System


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APPLICATION OF CURRENT TRANSFORMER CT


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MCSA Instrumentation


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Time Domain signals and Current Spectra


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CURRENT SIGNATURE DUE TO BROKEN BARS

LOWER

SIDEBAND

f1 =SUPPLY FREQUENCY (60 Hz)

Hz

dB

UPPER

SIDEBAND


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SIGNATURE PATTERN DUE TO BROKEN BARS

TWICE SLIP FREQUENCY SIDEBANDS : 2sf1

fsb = f12sf1

-2sf1 +2sf1

f1dB

Hz

IDEALISED

Current Spectrum Due to

Broken Rotor Bars


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MCSA ON GM3802A (January, 2002)

3-PH, HV, SCIM, 4155HP/3.1MW, 11kV, 2974r.p.m., 195A 50 Hz

BROKEN ROTOR BARLIFTED OUT OF THE SLOT

N=46 dB

William T. Thomson EM Diagnostics Ltd 2001 - unauthorised copying,

reproduction or amendment of all or part prohibited


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3-PH, HV, SCIM, 4155HP/3.1MW, 11kV, 2974r.p.m., 195A

BROKEN ROTOR BARLIFTED IN THE SLOT

SECONDARY DAMAGE TO HV STATOR

William T. Thomson EM Diagnostics Ltd 2001 - unauthorised copying, reproduction or amendment of all or partprohibited


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3-PH, HV, SCIM, 4155HP/3.1MW, 11kV, 2974r.p.m., 195A

BROKEN ROTOR BARLIFTED IN THE SLOT

SECONDARY DAMAGE TO HV STATOR

OFFSHORE OIL PRODUCTION PLATFORM

TOTAL REPAIR COSTS : $270,000.00

(Removal, transport, repair & re-installation costs)

THE BOSS IS NOT HAPPY

PREVENT THIS HAPPENING AGAIN

YOUR JOB IS ON THE LINE


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Case History : Large Sea Water Injection Pump

3-Phase SCIM, 6600V, 60Hz, 3.6MW/4285h.p.,376A,3580r.p.m., Star connected

Full-load slip? s=(Ns-Nr)/Ns = 0.0055(0.55%)

Sidebands = 2*0.0055*60 = 0.67 Hz (at full load)

or

Pole Pass Sidebands = 2 *(60 - 59.667) = 0.67 Hz


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1985 : 20 BARS BROKEN OUT OF 46


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INDUCTION MOTORGEARBOX COMPRESSOR

3phase, 415 V, 134 kW/180 H.P., 210 A, 1485 r.p.m., 50 Hz R = 58

1982 150 A


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DIE CAST ROTOR FAULTY END RING

INSPECTION FOLLOWING ON-LINE MCSA

William T. Thomson EM Diagnostics Ltd 2001 - unauthorised copying, reproduction or amendment of all or part prohibited

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