Reactors in Power Factor Corrector

I believe you asked this same question yesterday. It is 5 posts down. No need to keep asking the same question. Is this a homework problem?

www.ziddu.com/download/5518855/Detunedreactorcalculation.pdf.html

Don't let the model cause you a problem

Dear Sir,

1) You are not correct that all 7% detuned frequency capacitor bank systems does not depend on the value of Inductance and capacitance.In our case the reactance of reactor (XL)bear definite relationship with respect to capacitive reactance (XC)of Capacitor.This relationship is % percentage of reactance of reactor with reference to capacitive reactance value.

.ie for various capacitive reactances values of XC (various capacitor values), the inductive reactances (XL) valus bear a proportional relation ship ieXL= 7% of XC.

As long as this relationship between XL and Xc is maintained the detuned frequency is same for various values of inductor and capacitor.

XL=n% of Xc in the case of n% detuning desired

At resonance hXL= Xc/h , where h is tuned resonance frequency

Hence Detuned frequency h= Sqrt(Xc/XL)

h=Sqrt(XC/ n% xXC)

h=Sqrt(100/n)

Where h =detuned frequency

n= % of reactance

From the above it will be clear that detuned frequency depends on the % (n)of reactance value with respect to capacitance value

Thank you very much all

I have understand that the resonance frequency will be the same for all 7% detuned reactors(i.e. 189 H in case of 7%detuned banks) whatever the specific value of the capacitor and inductor is as long as the reactance of the reactor is 7% of the reactance of the capacitor at the fundamental frequency. This is also true for other n% detuned banks.

But what are the specific criteria's to chose either 7%, 14%or any other detuned reactors .I know that we use detuned banks when the THD (total harmonic distortion) is above 20%.

And power factor corrector suppliers asks for what type of factory we want the power factory corrector board for and based on that they decide what type of corrector we need (whether we need simple capacitor banks or detuned banks or active filters). I have searched on the internet to find information about these but I couldn't find any if u have any idea or if u can suggest me websites that will be helpful.

With kind regards

Dear Sir,

1)Please note that detuned reactors are used in series with powerfactor improvement capacitors to shift the first characterstic harmonic frequency (5th) If there is no reactor connected to Pf capacitor then parallel resonance (Very high current flow)may occur at the first harmonic frequency ie 5Th harmonics(250hz).inorder to prevent occurence of this parallel resonance at 5Th harmonics, the detuned reactor is used.with capacitor bank.This will shift the parallel resonance frequency away from 5th Harmonic frequency.Hence it is called detuned filter.As such your assumption that detuned filters are used when THD is more than 20% is not valid one.

2)The lowest harmonics frequency is 5Th in power system.Hence detuned reactors are always tuned well below this 5th harmonic frequency

3).The capacitor and detuned reactor are tuned to 189Hz ie with 7% detuning and with 14% detuning reactor,the system is tuned to frequency of 133Hz.With these reactors it is seen that filters are detuned well below 5th Harmonicie 250Hz.

4)As it is detuned filter, the harmonic filtering efficiency will only be 30-50%.If more filtering is needed then 7% detune filter is used as it is nearer(189Hz) to 5Th Harmonics tuned one (250Hz).In this case filtering will be more effective.If we choose14% detuning, (133HZ)then filtering effect will not be much compared to 7%detuning filter.

However considering filtering efficiency required , current limiting during switching and economic consideration weighs to go 7% or 14%

More information regarding filter banks,detuned filter banks, Active filter etc can be found in Nokian capacitor or ABB web site.

trust i have made myself clear to you

regards

V.Ambarani

Thank you for your fast response

As you have explained it well the first purpose of using detuning reactor is to shift the resonance frequency from the harmonic frequencies but detuning reactors have also the effect of reducing the harmonic distortion level .using capacitor bank(without detuning reactor )increase the harmonic distortion level further and the harmonic distortion level should be in the acceptable range. I have read that sometimes that we have to use reactors with capacitors to decrease the harmonic distortion level into acceptable range and above20 %total harmonic distortion is unacceptable. That is why I have said if the total harmonic distortion is above 20% we have to use reactor.

With best regards

nebiyou Quote "That is why I have said if the total harmonic distortion is above 20% we have to use reactor."

You still do not understand

Nebiyou

Maybe this will help http://www.galco.com/circuit/PFCC_har.htm

Quote Nebiyou "That is why I have said if the total harmonic distortion is above 20% we have to use reactor."

Did not see this mentioned in the article. You may use a reactor at any % distortion. A tuned unit is the way you rid the system of the offending harmonic.

dear wareeagle

thank you for your responce but i think you didn't read what i wrote very well. i know we can use reactors at any distortion. but i think we didn't simply put reactor with capacitor (it will be useless ).first we have to analyse the network harmonics first and based on these we have to check where the natural frequency lies ( natural frequency b\n the network impedance and the capacitor bank) and we have also to see the TOtal harmonic distortion level.(to see whether it is acceptable or not).and i said that if the total harmonic distortion is above 20% it is not acceptable and it should be reduced and since the detuned reactor have this capability we should use the reactors .YOU CAN REFFERE THE SHNIDER CASHIER TECHNICAL NOTE.

PLEASE READ THE FULL POST FIRST AND THE WAY YOU WRITE IS ..

great info