Abstract —
To avoid unexpected equipment failures and
obtain higher accuracy in diagnostic for the predictive
maintenance of induction motors, on-line health monitoring
system plays an important role to improve the system reliability
and availability. Among different techniques of fault detection,
work on motor current signature analysis by using only stator
current spectra has been well documented. In addition, the
recent developments in MEMS technology shows increasing
trend in integrating vibration analysis for fault diagnostic.
Vibration-based detection by using the accelerometer is gaining
popularity due to high reliability, low power consumption, and
low cost. This paper presents the study of vibration due to the
rotor imbalance. The technique of vibration detection and
observation of vibration signal in the 3-phase induction machine
is studied. A novel health monitoring system of electric machine
based on wireless sensor network (ZigBee™/IEEE802.15.4
Standard) is proposed and developed in this paper.
Experimental results of the proposed severity detection
technique of rotor vibration under different levels of imbalance
conditions are investigated and discussed.
Index Terms – ZigBee, wireless sensor network, induction
motors, health monitoring system, vibration detection
I. INTRODUCTION
The focus in most industry is shifting from scheduled
maintenance to the predictive maintenance by constantly
observing and predicting the machine condition in advance
[1]. Predictive maintenance by condition based monitoring of
electrical machine is a scientific approach that becomes new
strategy for maintenance management. Most industrial
motors are being monitored using vibration, current, and
temperature sensors which either provide warning signals or
shut down the system before any catastrophic failure occurs.
Though they are able to prevent permanent damage to the
machine, they can neither predict the usable life of the
equipment nor provide the severity level of the problem. This
resulted in the need of an advance system called on-line
health monitoring system.
Traditionally, health monitoring system is realized in
wired systems formed by communication cables and various
types of sensors. The cost of installation and maintenance are
difficult and expensive especially when the equipments are
not at the same location. To overcome these restrictions,
using wireless sensor networks for monitoring is proposed in
this paper. Wireless sensor network [2]-[3] is a new control
network that integrates sensor, wireless communication and
distributed intelligent processing technology. ZigBee is a new
wireless networking technology with low power, low cost
and short time-delay characteristics. These favorable features
are suitable for our application.
Most recent research has investigated the fault detection
technique primarily based on the Motor Current Signature
Analysis (MCSA) [4]-[5] with various DSP and signal
processing techniques [6]. Although the fault detection by
means of analysis of the current is quite simple, the main
drawback is that the employed technique is only suitable for
steady state operation. Since the rotor imbalance is
mechanical related problem, the possibility of an analysis of
machine vibrations is obvious. In [7], by using machine
vibration analysis, the technique of detecting electrical fault
such as voltage unbalance is explored but the mechanical
fault and the level of the severity are not yet discussed.
This paper proposes and develops a ZigBee based
wireless sensor network for health monitoring of induction
motors. The vibration signals obtained from monitoring
system are processed with signal processing techniques. In
order to predict the level of severity of rotor imbalance, the
vibration detection techniques with suitably modified
algorithms is used to extract detailed information for
induction machine health diagnostic.
II. THE PROPOSED WIRELESS HEALTH MONITORING SYSTEM
As shown in Fig. 1, the proposed wireless health
monitoring system comprises of PWM Inverter, Induction
motor and load station. The three-axis accelerometer is used
to measure the vibration of the motor.

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