Transformer Losses compensation

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Besoeker said:
OK. I looked at this for the highlited 1000kVA entry.
The 72.4kVAr would make the PF of the transformer at full load about 0.997.
Do you really want to correct for that?
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yes exactly i was looking to compensate for this. But the P.F=0.997 Near to unity, you mean no need for correction.??
 
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Sajid khan said:
yes exactly i was looking to compensate for this. But the P.F=0.997 Near to unity, you mean no need for correction.??
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As per my knowledge it is preferred that we keep away from that unity PF, What about the affect of the capacitive loads we may take the PF to exceed unity So all the motor will inject current, which is not required and has some dangers consequences like i.e insulation damage.
 
Sajid khan said:
yes exactly i was looking to compensate for this. But the P.F=0.997 Near to unity, you mean no need for correction.??
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I wouldn't. The normsl customer spec is for load side correction to 0.95. The risk of correcting a PF so near unity is that you may go into leading PF and that can cause the volts to increase.
 
Besoeker said:
I wouldn't. The normsl customer spec is for load side correction to 0.95. The risk of correcting a PF so near unity is that you may go into leading PF and that can cause the volts to increase.
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This appears to be a case of "close enough is good enough". Do not let the perfect be the enemy of the good.
 
gadfly56 said:
This appears to be a case of "close enough is good enough". Do not let the perfect be the enemy of the good.
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I wouldn't have put it that way. At the load side, we can make the PF what we want it to be - not just good enough.
 
Besoeker said:
I wouldn't have put it that way. At the load side, we can make the PF what we want it to be - not just good enough.
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I was unclear; I meant in this specific instance that there was little to be gained from trying to improve a PF of 0.997 (good) to 1.000 (perfect).
 
Sajid khan said:
yes exactly i was looking to compensate for this. But the P.F=0.997 Near to unity, you mean no need for correction.??
Click to expand...
Load PF correction is typically done on the load side of the transformer... and closer to individual load level rather than at the supply for all connected loads. How and where it is handled is somewhat dependent on whether you a continuous or mostly non-continuous operation. If the major loads are operating 24/7/365, you can correct anywhere up line. If you have all start-stop major operations, you want correction for each load. In between is a compromise born from analysis.

This approach prevents or helps to prevent overcorrection mentioned by others.
 
gadfly56 said:
I was unclear; I meant in this specific instance that there was little to be gained from trying to improve a PF of 0.997 (good) to 1.000 (perfect).
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Correction to unity PF is best avoided.
A small change in loading can result in leading PF which can cause a rise in the voltage being supplied.
That's one of the reasons our customers, mostly industrial, specified 0.95.
 
Besoeker said:
Correction to unity PF is best avoided.
A small change in loading can result in leading PF which can cause a rise in the voltage being supplied.
That's one of the reasons our customers, mostly industrial, specified 0.95.
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Being unafraid to display my ignorance, can you explain how this happens? Not having to deal with it very much, my understanding of PF is a little thin.
 
gadfly56 said:
Being unafraid to display my ignorance, can you explain how this happens? Not having to deal with it very much, my understanding of PF is a little thin.
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You have to draw out the vector diagram.....

Lead-Lag_zps41595276.jpg
 
Smart $ said:
Load PF correction is typically done on the load side of the transformer... and closer to individual load level rather than at the supply for all connected loads. How and where it is handled is somewhat dependent on whether you a continuous or mostly non-continuous operation. If the major loads are operating 24/7/365, you can correct anywhere up line. If you have all start-stop major operations, you want correction for each load. In between is a compromise born from analysis.

This approach prevents or helps to prevent over-correction mentioned by others.
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Smart can you tell from what HP rating of motor it is recommended to put individual compensation? what i know, i read somewhere, is for motor 250HP and above.
 
Besoeker said:
Correction to unity PF is best avoided.
A small change in loading can result in leading PF which can cause a rise in the voltage being supplied.
That's one of the reasons our customers, mostly industrial, specified 0.95.
Click to expand...

yes all this discussion is very nice, but till now i am not getting the exact what i required.


Let me explain my problem again in other words, for a 3150kVA transformer we required power factor correction capacitor bank in order to improve the power factor of the load connected to the transformer e.g for a 3150kVA transformer we calculate the required capacitor banks size to be 700kVAR. Do i still need to add the KVAR compensation required by transformer for the reactive energy absorbed by transformer alone i.e (700kVAR+0.09x3150kVA= 983.5KVAR). This 0.09 is as per the Schneider guide as attached and mention that it is to be added (see red highlighted box). I didn't do this before in any project but my senior engineer is of the view to add this extra kVAr to size the capacitor bank.
 

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Sajid khan said:
Smart can you tell from what HP rating of motor it is recommended to put individual compensation? what i know, i read somewhere, is for motor 250HP and above.
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No. PFC (power factor correction) is not really my bailiwick. There are other forum patrons better suited to advise you.
 
If I understand you correctly, are you are asking if you should add the compensation that would be required for the transformer with no load, to the compensation that would be required for the motor to get the "total" compensation?
 
electrofelon said:
If I understand you correctly, are you are asking if you should add the compensation that would be required for the transformer with no load, to the compensation that would be required for the motor to get the "total" compensation?
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Yes this is what i mean.. i.e Transformer alone KVAR requirement+ all other loads
 
Sajid khan said:
yes all this discussion is very nice, but till now i am not getting the exact what i required.


Let me explain my problem again in other words, for a 3150kVA transformer we required power factor correction capacitor bank in order to improve the power factor of the load connected to the transformer e.g for a 3150kVA transformer we calculate the required capacitor banks size to be 700kVAR.
Click to expand...
It's the load you need to compensate for. Not the transformer.
 
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