Power factor in different voltages

  • Thread starter asmani
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  • #1
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Main Question or Discussion Point

Hi all.

In the following circuit, z is an inductive load (I mean inductance + resistance).

2qxxrhc.png


Here is the table of cosφ measured by power factor meter in different voltages:

2wna6nc.png


Why it's increasing? Isn't cosφ independent of the voltage of the autotransformer?
 

Answers and Replies

  • #2
1,356
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The inductance of the AutoTrans is changing as you adjust the voltage - try the same test with purely resistive load.
 
  • #3
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Thanks Windadct.
Isn't power factor meter just measuring load voltage? If yes, how can inductance of the AutoTrans effect?
(For purely resistive load, the increase was lesser.)
 
  • #4
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The PF meter is really measuring the Phase angle between the V and I - this relationship is affected by everything in the circuit - including the AutoTrans.

So if your load was a pure resistor - the phase shift would be due to the Inductance of the Autotrans - at the different adjustment points. Techincally the total impedance of the source feeding the AutoTrans will have an effect as well - but not as pronounced as the data you are showing, unless you have a "weak" source like a isolation transformer - etc.
 
  • #5
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What do you mean by V?
How the inductance of AutoTrans changes, increase or decrease?
Thanks again
 
  • #6
1,356
337
V voltage and I current - the basic PF meter really measures the phase angle between the two - not a real power factor - but close enough for a lab exercise.

As for will the Inductance increase or decrease - I do not know - but looking at your data - what is your guess?
 

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