A Review of On-Line Condition Monitoring
techniques for Three-Phase Squirrel-Cage Induction motors-Past,
Present and Future
W.T.Thomson, Senior member, IEEE
The Robert Gordon University, Schoolhill, Aberdeen, Scotland
Published: July 2002
Abstract
The main objective of this review is to provide
industry with state of the art knowledge on condition monitoring
strategies for assessing the operational health of induction motor
drive systems. An overview of typical failure mechanisms and their
causes is presented. the essential criteria for reliable condition
monitoring system are discussed and the theoretical principles
behind the generation of unique signal characteristics, which are
indicative of failure mechanisms, are presented. On-Line monitoring
techniques which can be used to diagnose mechanical problems, stator
and rotor winding failure mechanisms, and airgap eccentricity are
described. the focus is on vibration, current, flux and partial
discharge monitoring strategies. the application of monitoring
systems in industry is reviewed and reference is made to on-site
case histories. Recent developments, including the use of monitoring
and analysis of electric current to diagnose mechanical problems is
discussed. Future requirements for monitoring and diagnosing faults
and fundamental causes in modern induction motor drives are
presented.
Full Text (PDF)
Introduction
The Operators of electrics drive systems are
under continual pressure to reduce maintenance costs and prevent
unscheduled downtimes, which result in lost production and financial
income. many operators now use on-condition based maintenance
schemes. this has reduced unexpected failures, increased the time
between planned shutdowns for standard maintenance and reduced
operational-costs.
The operation of electrical machines in an unsafe
condition can also be avoided. Since the incidence of unexpected
failures is reduced the operator is able to exercise grater control
in the prevention of incidents which may have environmentally
damaging consequences. in hazardous installations, this requires
continuous on-line monitoring to prevent a catastrophic failure.
During the past fifteen years there has been a
substantial amount of research into the creation of new condition
monitoring techniques for induction motor drives. New methods have
been developed which are now being used by the operators and
research is continuing with the development of new and alternative
on-line diagnostic techniques. However, it is still the operators
who have to make the selection of the most appropriate and effective
monitoring systems to suit their particular induction motor drive
systems. Due to the variety of diagnostic techniques now available
this is not an easy task and this review aims to provide the user
with up to date knowledge on monitoring and diagnostic systems for
induction motor drives.
Fig 1: Current Spectrum for a 1.45MW, SCIM with
abnormally high (35%) airgap eccentricity.
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