VFD-Long Term Affect on Motors 1

[jOmega]

Any one know of or able to provide a reference to a study on the long term affects of VFDs on motors ?

Colleague in Italy has asked for some information thereof.

Much appreciated.

jOmega

 

[jbartos]

Suggestion: Visit

http://www.mt-online.com/articles/0403_motors.cfm

for: motor wear due to ASD

http://www.nalanda.nitc.ac.in/nitcresources/ee/lectures/lectures/Asd.pdf

for: motor protection against ASD

http://www.xpedio.carrier.com/idc/groups/public/documents/marketing/808-259.pdf

for: Reduced motor wear
etc. for more info

 

[jOmega]

Thanks, JB.

Comments:

Need to be very careful in the useage of your first reference as it is very outdated; it appears author used research material from a bygone era; i.e., 20-25 years ago when six-step technology was state-of-the-art.

Today's PWM using sinecoded, Voltage Vector, Space Vector technology have a much more motor-friendly output waveform with reduced harmonics introduced into the motor. If you were to compare the waveform of Fig. 2 in Ernesto Wiedenbrug's article, with a PWM waveform of the type referenced herein, you would see that the current waveform resulting from today's technology is very nearly sinusoidal with extremely low harmonics. Some testing with a VVC scheme showed that the harmonics were very low and that heat rise over pure sinusoidal was less than 5% worst case.


What my colleague is looking for is a paper that compares the life of a motor operated DOL on sinewave power for some fininte period time as opposed to a motor in the same application for the same period of operating time, operated on VFD power.

If such studies exist, they may be burried within the electric motor industry... as I don't recall having seen anything published in any of the tech or trade journals.

Appreciate your taking the time to look and report.

Regards,
jO

 

[GGOSS]

Hello JOmega,

Although I cannot point you to a specific document, I do know that the people at WEG have conducted extensive research into that specific area and in fact use the information (along with other stuff) as a basis for promoting the use of inverter duty motors.

You might wish to contact the people at your nearest WEG motor outlet......with fingures crossed.

Regards,
GGOSS

 

[jOmega]

GGoss,

Thanks much. At your suggestion, I have a call in to my local WEG rep who just happens to be a colleague I worked with for many years in other places.

Much appreciated.

jO

 

[Boerewors]

Hi jOmega,

I would like to know if you found any info regarding this subject and if you would be willing to share it with me.

I am doing an investigation on the impact of VSDs on motor lifetime(LV only)

I'd appreciate it if you can help.

thanx

 

[ozmosis]

I have a few white papers on:
"The effects of shaft voltages and Bearing Currents on Inverter driven Induction motors"
"Motor Insulation and VSD's"
The latter being a Siemens specific article but there's a section on the comparison of DOL and VSD operation.
I can email them to you if you wish but not sure of the protocol in these forums of doing this.

 

[Boerewors]

Hi Sed2dev.

Thanx, that would be great. I'm not sure about the protocol either, but here is my email address in any case:

Martinus.Beumer@sasol.com

I appreciate it. Thanx

 

[jbartos]

Suggestions to jOmega (Electrical) Oct 26, 2003 marked ///\\\
Need to be very careful in the useage of your first reference as it is very outdated; it appears author used research material from a bygone era; i.e., 20-25 years ago when six-step technology was state-of-the-art.
///No specific preferences were posted in the original posting. If you are seeking the state-of-the-art, you should state so.\\Today's PWM using sinecoded, Voltage Vector, Space Vector technology have a much more motor-friendly output waveform with reduced harmonics introduced into the motor. If you were to compare the waveform of Fig. 2 in Ernesto Wiedenbrug's article, with a PWM waveform of the type referenced herein, you would see that the current waveform resulting from today's technology is very nearly sinusoidal with extremely low harmonics.
///Agree. They are also more expensive. Also, I see that VFD manufacturers are reluctant to provide VFD output waveforms, e.g. a snapshot of the oscilloscope screen.\\ Some testing with a VVC scheme showed that the harmonics were very low and that heat rise over pure sinusoidal was less than 5% worst case.
///Agree. However, the very recent VFD output waveform from larger VFD manufacturer exhibited visible VFD output waveform distortion. Since no specific references are provided or links posted, one has to go by what is available from a VFD manufacturer per standard off the shelf VFD product. Visit

http://www.esmagazine.com/CDA/ArticleInformation/features/BNP__Features__Item/0,2503,60412,00.html

for more uptodate link.\\
What my colleague is looking for is a paper that compares the life of a motor operated DOL on sinewave power for some fininte period time as opposed to a motor in the same application for the same period of operating time, operated on VFD power.
///Since there are various VFD output waveform qualities, the requirement needs to be narrowed down to a specific VFD topology and perhaphs to a specific manufacturer.\\