Two Minute Tips  

Stator Mechanical Faults Using Electrical Signature Analysis (ESA)

Mark Koch
Mark Koch | Technical Support Manager, ALL-TEST Pro, LLC

Stator Mechanical Faults Using Electrical Signature Analysis (ESA)

A stator mechanical fault is created when the stator core becomes loose within the motor frame, or if the windings are loose between the stator slots. A loose stator core or winding over a period of time will cause a breakdown in either the winding insulation system or insulation system to ground. Electrical Signature Analysis (ESA) evaluates the current and voltage spectrums using a Fast Fourier Transform (FFT), which converts the time waveform to a frequency spectrum. The FFT highlights amplitudes and frequencies identifying mechanical faults such as problems with the stator.

When there are peaks at the same frequency in the current and voltage spectrums, they are related to the incoming power. When there are peaks only in the current and not the voltage, then the fault is coming from either the motor or the driven load. In the ESA example above a stator mechanical problem is indicated by line frequency sidebands of running speed multiplied by the number of stator slots. The red arrows identify stator mechanical frequency peaks in the current spectrum and not in the voltage.

Subscribe
Notify of

This site uses Akismet to reduce spam. Learn how your comment data is processed.

2 Comments
Oldest
Newest Most Voted
Inline Feedbacks
View all comments
Radhakrishnan CG
7 months ago

does the same apply to generators also?

Bill Kruger
7 months ago

No this is true for AC 3 phase motors.

About the Author

Mark Koch
Mark Koch Technical Support Manager, ALL-TEST Pro, LLC

Mark Koch is a member of the Technical Support team at ALL-TEST Pro, LLC (ATP), where he has provided professional support worldwide for users of ATP equipment since 2014. He has 17 years of electrical and reliability maintenance experience. In 2001, he started his career as a construction electrician. During this time, he worked his way up from shop floor apprentice to a foreman in charge of starting and completing remodel and new construction projects. In 2010, he began working at the Metropolitan Sewer District (MSD) of Greater Cincinnati, Ohio, USA, where he learned electrical maintenance best practice and helped implement a predictive maintenance program (PdM). During his service at MSD, his team was the recipient of both the Uptime Magazine’s Best Emerging Maintenance Reliability Program Award and the Uptime Magazine’s Best Asset Condition Management Program Award. At MSD, he learned and provided routine PdM services such as thermography, vibration, lubrication, visual inspection, motor testing, and ultra-sonics.

 

Education and Certifications:

2001-2006- International Brotherhood of Electrical Workers (IBEW) Apprenticeship Program and the National Electrical Contractors Association (NECA) Inside Wireman Certification.

2013- PdM Visual Testing Level 2 Certification & Level 1 Thermographer Certification; 2014- Vibration Analysis Level 1T Certification.