Guide to Fault Diagnosis of Induction Motors -- Contents and Intro

Contents

0. Introduction (this page; see below Contents)

1. Condition monitoring and fault diagnosis of induction motors

2. Theory of line-start and inverter-fed induction motors

3. Induction motor faults: basics, developments and laboratory-scale implementation

4. Magneto-motive force waves in healthy three-phase induction motors

5. Multiple-coupled circuit model of induction motors

6. Finite element implementation of induction motors in healthy and faulty conditions

7. Signal-processing techniques utilized in fault diagnosis procedures

8. Diagnosis of broken bars fault in induction motors

9. Diagnosis of eccentricity fault in induction motorss

10. Diagnosis of interturn short-circuit fault in induction motors

Introduction

Induction machines are used more extensively than any other form of electrical machines. Low voltage machines are often used in domestic applications. However, larger induction machines with higher power and voltage ratings are widely launched in industrial environment such as pumps, mines, petrochemical and electrical power generators in order to provide motive force for major services.

Nowadays, the responsibilities of induction machines are continuously growing, and the reliable operation of induction machines is strategically very important for providing essential services.

There are many faults which can prevent smooth operation of induction machines. Generally, any fault starts as a small declination from the healthy normal operation. Then, it may lead to a catastrophic failure if the fault is not detected and treated at its early stages. Therefore, a concept called ''condition monitoring'' of induction motors is introduced. Condition monitoring is a process of detecting and diagnosing fault-related changes of an essential motor quantity. Such action allows to schedule a proper maintenance, prevents failure, avoid significant damages, avoid economic lost, stop outages, optimizes the performance and enhances the quality control.

This guide originated from the experience of the authors during researching fault diagnosis of induction machines at University of Toldeo (Ohio, USA), College of Engineering. Our research has led to many publications in induction machine fault detection, some have been referred in the guide. This guide is intended to help electrical engineers in industries and postgraduate/graduate students who would like to do research in this area or similar topics. Moreover, this guide in an endeavor to collect recent attempts in the field of diagnosis of induction motors and sort them in a meaningful way so that potential readers can find a hierarchical discussion on different types of faults. This includes basics, developments, simulation approaches and experimental measurement of three important type of faults, namely the broken bars, eccentricity and interturn faults.

The guide has been managed to cover fundamental and advanced aspects of the previously mentioned types of faults by providing step-by-step theoretical, analytical, numerical and experimental implementations. Basically, there are ten sections as follows:

Section 1 provides a preliminary discussion on different types of faults and the corresponding influential factors in induction machines. Then, the necessity of the fault diagnosis procedures and their importance in maintaining a safe industrial environment are highlighted.

Section 2 explains the fundamentals of motor-drive operations in different supply modes including the line-start and inverter-fed applications in order to prepare readers for the next sections.

Section 3 is probably the heart of this guide since it provides a fundamental to advance knowledge of different types of faults, namely the broken bars, eccentricity and short-circuit faults. Moreover, a useful implementation technique of different faults and the corresponding measurement are discussed.

Section 4 addresses detailed analytical analysis of healthy induction motors. This section is considered as the basis for analyzing the time and space harmonics of induction motors, which will be used to extract fault indicators in the next parts of the guide.

Section 5: The winding function theory is one of the most useful analytical modeling approaches of different types of faults in induction motors, which is explained in this section. The broken bars, eccentricity and short-circuit faults will be formulated using the winding function theory and some typical results of the corresponding simulation process are introduced.

Section 6: As the most reliable simulation process of electrical machines and their defects, the finite element method is targeted in Section 6. The mathematical implementation of the approach is provided first. Then, the way to implement different types of faults is discussed.

Section 7: Time, frequency and time-frequency signal processing techniques are explained and the corresponding MATLAB codes are provided in Section 7 so that one can easily use the programs to conduct further signal processing applied to different signals of faulty motor.

Section 8: The broken bars fault is the main focus of Section 8. In this section, various aspects of the corresponding diagnosis process are provided in order to get a better realization of how the broken bars fault is detected and diagnosed in different operating conditions. Different drive systems, various load levels, various speed levels and different indicators are addressed.

Section 9: The same process as that of Section 8 is followed in Section 9 in order to address the issues related to the eccentricity fault. Two main types of faults including the static and dynamic eccentricity faults are investigated by means of time and frequency analysis.

Section 10: The short-circuit fault will be studied in Section 10. Different time and frequency domain techniques will be used to address the challenges related to diagnosis of the short-circuit fault. Two types of machines, namely the wound and squirrel-cage induction motors, are investigated.

-------

So many postgraduate/graduate students have helped with the preparation of the present guide that we cannot properly acknowledge them all and this guide would never have been possible without their excellent research over the last 19 years. We would specially like to thank University of Toldeo for its previous financial supports of the projects whose outcome has been gathered here as a guide.

Also see: Guide to Electric Motor Maintenance and Troubleshooting