Background

The history of condition monitoring and fault diagnosis is as old as the induction motor itself. Induction motors initially relied on simple protection such as over-current and over-voltage to ensure safe operation. In spite of these tools, many industries are facing unexpected system failures and reduced motor lifetime. Induction motors utilisation grew increasingly complex, condition monitoring and fault diagnosis of these motors becoming mandatory. Considerable diagnostic strategies and control schemes were devised to ensure a fault-tolerant control drive. Redundancy and conservative design techniques have been adopted for improving the reliability of induction motor drive systems against a variety of faults and its implementation is expensive. Condition monitoring leading to incipient fault detection and prediction of induction motors has attracted many researchers. Early detection and correct diagnosis of incipient faults could allow preventive maintenance to be performed and provide sufficient time for controlled shutdown of the affected process. They can reduce financial losses and avoid catastrophic consequences.

Objective

CSIO Chennai Centre proposed to develop Cost effective, non intrusive Motor Stethoscope to Monitor the induction motor health & diagnose the fault using the latest art of instrumentation. The system will be cost effective, and reliable for monitoring the health of Induction Motors on-site & online.

Methodology

Condition monitoring and fault diagnosis of engineering plant has increased recently because of the widespread use of automation and consequent reduction in direct human-machine interaction to supervise the motor drive system operation. Due to its low cost, reasonably small size, and operation with an easily available power supply, induction motor is widely used in industries such as automotive, aerospace, and industrial equipment. However, operational environment, duty, and installation issues may combine to accelerate induction motor failure far sooner than the designed motor lifetime. Faults can occur in the stator, rotor, bearing, or the external systems connected to the induction motor. These faults can produce one or more of the symptoms as follows:

• Unbalanced voltages and line currents
• Vibration and noise
• Torque pulsations
• Excessive heating
• Leakage flux
• Other symptoms

An ideal condition monitoring and fault diagnosis scheme should take the minimum measurements from a motor and by analysis extract the signals feature. A condition can be inferred to give a clear indication of incipient fault modes in a minimum time. Condition monitoring has to establish a map between input signals and output indications of the motor condition. Developed prototype is shown and it is under testing.