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TRANSCRIPT
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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
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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%)
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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
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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
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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