The results of fault studies help the machine designers to
improve the fault tolerance as well the overall design of the
machine drive system. For industrial processes, the Induction
motor fault monitoring and diagnosis is important to identify
motor failures before they become catastrophic and to prevent
severe damage to induction motors. Undetected minor motor
faults may cascade into motor failure, which in turn may cause
production shutdowns. Such shutdowns are costly in terms of
lost production time, maintenance costs, and wasted raw
materials. In the past two decades, there has been substantial
amount of research to provide new condition monitoring
techniques for ac induction motors based on analyzing
vibration signals, or signals other than currents. Vibration
transducer is expensive and care should be taken into account
for mechanical installation and transmitting the signal [4].
Similar problems exist while working with other sensors like
speed and temperature. Interestingly, signatures of all signals
are available on electrical terminals of electric machines
including the vibration signals [5]. Current signals can easily
be monitored for condition monitoring and control purposes.