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Power factor of induction motors/generators paralled to a utility(infinite buss)


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#1 James K

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Posted 18 October 2002 - 12:44 AM

Q?

Does the power factor of a induction motor or generator change based upon the motor charactoristics OR does the power factor of the electrical system affect it.

Case in point, if a motor or generator operated at the same load, voltage, etc. at one location with a measured p.f. of .85 ( at the motor- while operating), and a site p.f. of .90 (while the motor is off ) change.... if the motor is moved to another location where the site p.f. is .95?

:(

#2 marke

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Posted 18 October 2002 - 08:27 PM

Hello James K

The power factor of a motor is a function of the motor design and the load on it. Changing locations will not alter the power factor provided that the voltage and frequency are the ame.
Variations in supply voltage and supply frequency will alter the power factor.

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#3 James K

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Posted 18 October 2002 - 08:48 PM

Marke,

This is what I suspected, I am working with manufacturer who builds combined heat and power systems using natural gas/propane fuel industrial engines to drive an induction motor. Their control system monitors voltage, amperage and calculates kW with a fixed power factor # of .9 (they can adjust this value). We tested the generator while running with a portable kW meter (3 phase) and we measured .83-.84 power factor or 140kW compared to their reading of 147kW. The mfg. stated, "well the power factor at the site will probably be around .9, therefore we set the power factor number in the monitoring system to match the site power factor.

This does not make sense as the kW of the generator would change from location to location if this was true, secondly, the heat rate (btu/kW) would also change from site to site. Can you recommend any documents that I can print and send to this manufacturer? They are deceiving their customers and appear to be uneducated in the measurement and effects of magnitizing currents, iron losses, copper losses, etc. etc.

Thanks for your feedback. Do you CHP in New Zealand?;c;;c;

#4 marke

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Posted 19 October 2002 - 09:46 AM

Hello James K
Yes you are correct, they are incorrect in assuming the power factor, and the site power factor is irrelevent. The motor power factor is the important issue and it will change depending on shaft torque and terminal voltage.
It is surprising how many such simple errors are made, suggesting that there is a major lack of understanding of the basics.
I am not sure where I can suggest to give a simple, definative and independent description of this. I have established this web site because of the general lack of information in this area. - fills a hole!
I could perhaps look at adding a description olnong the required lines somewhere on this site and you could stear them there. Would that help??
Perhaps someone else can suggest a suitable reference.

Not sure of CHP?? a new term on me!!

Best regards,

#5 James K

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Posted 22 October 2002 - 03:32 PM

Thanks Marke,

I am not sure how much I can help but let mw know, I am researching the issue with the motor mfg. and the utility. The motor mfg. agrees but the feedback from the utility company does not agree!

CHP stands for Combined Heat and Power aka Cogeneration. Two or more forms of useful energy from one source, i.e. natural gas reciprocating engine operating and electric generator with the engine jacket water and exhaust heat being recovered and used for heating hot water, making steam or producing chilled water for air conditioning.

Overall efficienies approach 80% if all of the thermal energy canbe used.

Regards,;d;;d;;d;

#6 marke

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Posted 22 October 2002 - 05:53 PM

Hello JamesK

Makes sense now!!
We have a local company working in this area using a stirling engine. You can get more information at http://whispertech.co.nz/
Sometimes, it can be very difficult to get mind sets changed.
Good luck,
Best regards,




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