[BLDG-SIM] Motor efficiencies when driven by VFD

Bill bkoran at qwest.net
Fri Oct 12 13:11:12 PDT 2007

I'm looking for data pertaining to the subject.  I found information on
motor efficiencies at various loads, such as from the MotorMaster database
and a couple of research papers.  However, I haven't found clear information
on motor efficiencies when driven by VFDs.  Here are the types of
information that could be useful:

Efficiency vs. load at constant speed (have that for non-VFD applications) 
Efficiency vs. speed at constant load 

I'm also aware that VFDs can be setup different ways, but I don't know much
about this.  I suspect that how the volts per Hz varies impacts the motor
efficiency, so that type of information would also be valuable.

Or are VFD setups for HVAC applications inconsistent, so it is hard to

I am seeking this information because I am working on some spreadsheet
applications for the CEC (that will be available to everyone) for estimating
savings for changes to variable-flow systems (change to pressure setpoints,
resets, etc.)

Any relevant information would be helpful.  I may not be able to incorporate
all the information now, but I'd like to know (and eventually address!) any
shortcomings in my current applications.


William E. Koran, P.E. 
Senior Energy Engineer 
Portland Energy Conservation Inc. 
1400 SW 5th Avenue, Suite 700 
Portland, Oregon 97201 
Voice: 503-595-4441 
Fax: 503-295-0820 
Web:  <file://www.peci.org> www.peci.org 

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