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Diagnosing Faults in Electric Motors - Overview

Quick facts

This course will provide attendees with a very solid understanding of how induction motors, synchronous motors, and DC drives work, and how the VFD controllers work.  The course will discuss typical failure modes and a wide variety of diagnostic techniques including spectrum analysis, time waveform analysis, and motor current signature analysis.  In case your vibration analysis skills are a little rusty, the course will provide an introduction to the key concepts which must be understood; all use Mobius animations and simulators.  Trainees will also learn how their condition monitoring programs can be adjusted in order to better detect the fault conditions.  A range of case studies will be used throughout the course. 


2 days


Public and on-site training

The following course can be delivered on-site, or you can attend one of our public courses.  If held on-site, we can adjust the course content to meet your needs, and we can use your need


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   Onsite - This email address is being protected from spambots. You need JavaScript enabled to view it.This email address is being protected from spambots. You need JavaScript enabled to view it.for onsite training at your premises or choice of location

   Public courses - Find Dates and Venues

Who should attend this course:

This course would be of interest to all vibration analysts, as well as people involved with motor repair and electrical testing. If you are involved with a predictive maintenance program, or with plant operation or reliability, this course will provide essential knowledge that will help you keep the motors running.

Course Description:

 Understanding the operation of electric motors:

  • ·Induction motors,
  • ·Synchronous motors,
  • ·DC drives, and
  • ·Variable frequency drive (VFD) operation.

           Understanding failure modes of electric motors

What are the key forcing frequencies:

  • ·What does the 120 Hz peak relate to?
  • ·Calculating the synchronous speed and slip frequency
  • ·Calculating the pole pass frequencies
  • ·Frequencies associated with SCRs and IGBTs (VFD controllers)

A quick review of key vibration fundamentals

  • ·Harmonics
  • ·Sidebands/modulation
  • ·Beating

  Fault analysis with spectrum analysis (and selecting the best Fmax and LOR settings)

  • ·Induction motors
    • Soft foot
    • Stator problems
    • Eccentric rotors
    • Damaged rotor bars
    • Rotor bow
    • Loose rotor
    • Loose stator windings
    • Lamination problems
    • Loose connections
    • Motor current analysis


  • ·Synchronous motors
    • Loose stator coils and other common faults


  • ·DC motors and VFD controllers
    • Broken armature windings
    • Grounding problems
    • Bearing damage due to fluting (passage or current)
    • Faulty system tuning and other controller faults


Dealing with variable speed machines

  • ·How to perform vibration analysis when the speed and load will change
  • ·Resonance and variable speed machines


 A review of additional technologies:

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 A range of case studies will be presented

  • ·Static case studies that describe a number of fault conditions, including case studies that demonstrate the development of fault conditions over time
  • ·“Live” case studies where live vibration recordings will be played demonstrating some of the unique characteristics
  • ·Hands-on time will be spent with fault simulators