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SUBMITTED BY

VIBHA.IK

S7 E1

37156

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CONTENTS

INDUCTION MOTORS

FAULTS

DETECTION METHODS

PROPOSED DETECTION METHOD-VOLTAGEPATTERN ANALYSIS

EXPERIMENTAL SETUP

RESULTS

CONCLUSION

REFERENCE

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INDUCTION MOTORS

FANS

CENTRIFUGAL PUMPS

MOST MACHINERY TOOLS CRUSHERS

PUNCHING PRESS

TRACTION

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WHY INDUCTION MOTORS?

SIMPLICITY

RUGGED CONSTRUCTION

RELATIVELY LOW MANUFACTURING COST SPEED VARIATION

HIGH EFFICIENCY

HIGH POWER FACTOR

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FAULTS

Bearing faults

Stator interturn short-circuits

BROKEN BARS

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FAULTY ROTOR PERFORMANCE

o Distortion inmagnetic fielddistribution acrossrotor

o Asymmetricalmagnetic patternacross rotor

o

Deterioration ofmechanicalparameters

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EXISTING DETECTION METHODS

MOTOR CURRENT SIGNATURE ANALYSIS

POWER SPECTRUM ANALYSIS

DRAWBACKS

COMPLEX NUMERIC METHODS HIGH HARDWARE REQUIREMENTS

LIMITED ABILITY TO MAKE AN

ACCURATE DETECTION7

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PROPOSED METHOD-VOLTAGE

PATTERN ANALYSIS

Make use of easily accessible signals(line to

line voltage) for monitoring

Extract information on voltage oscillations

which serve as the basis for failure

determination

No advanced mathematical algorithms and

time demanding computations are needed

Simple method

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SPEED ADJUSTING

Inverter fed drives

Vector field control is used(FOC-field oriented

control,PTC-predictive torque control) Then filter high frequency components. Rotor

bars defect can be easily identified in low

frequency.

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BLOCK DIAGRAM OF PTC Outputs a

reference flux

value according

to the torque

demand. IFC generates

appropriate

voltage

references that

will drive the

inverter.

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BLOCK DIAGRAM OF FOC

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FOC

FOC is more accurate than PTC

Produces smoother output voltage pattern of

inverter

Widely used control approach

In this not only speed but also the flux is

compared

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EXPERIMENTAL SETUP

3kW IM

Rated Torque 20Nm

Speed 1500rpm

Squirrel cage rotor

44 rotor bars

7 broken bars

Constant load torque applied to shaft by means ofELECTROMAGNETIC BREAKS and measured usingDYNAMOMETER

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Contd.. Control algorithms implemented using TI

TMS320F28335 microcontroller. Laboratory built inverter linked control stage

to the IM.

Two line-to-line voltages measured withdifferent probes at the inverter terminals.

Filtration of obtained signal using 3rd order

low-pass filter with cut off frequency 36Hz.

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EXPERIMENTAL SETUP

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AVERAGE DUTY CYCLE IN TERMS OF

VARIANCE

Determines possible

faulty conditions

Determines degree

of error

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CONCLUSION The broken rotor bars manifest itself through

the oscillation in average voltage vectormagnitude impressed to the IM

When the magnitude of the oscillation(i.e.variance) exceeds a certain level , there will bea fault in the rotor of IM.

Detection relies on measuring phase voltages.

Easily implemented in inverter-fed drives.

Significant computational power not required.

Study the cases with even smaller number ofbars

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REFERENCE[1] ] P.J. Tavner, "Review of condition monitoring of rotating electrical

machines," Electric Power Applications, IET, vol.2, no.4, pp.215-

247, July 2008.

[2] M.E.H. Benbouzid and G.B. Kliman, "What stator current processing based

technique to use for induction motor rotor faults diagnosis?,"

IEEE Trans. Energy Conv., vol.18, no.2, pp. 238-244, June 2003.

[3] D. Pouliezos and G. S. Stavrakakis, Real Time Fault Monitoring of

Industrial Processes, Kluwer Academic Publishers, 1994.

[4]P. Vas, Parameter Estimation, Condition Monitoring, and Diagnosis

of Electrical Machines, Clarendon Press, Oxford, 1993.

[5] F. Filippetti, G. Franceschini, C. Tassoni, and P. Vas AI techniquesin induction machines diagnosis including the speed ripple effect,

IEEE Trans. Ind. Applicat., vol.34, no.1, pp. 98-108, Jan./Feb. 1998.

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