Input Power to Computers
Input Power to Computers
(OP)
We are working on design of a filter to filter out 3rd harmonics generated by SMPS of computers. However, when we conducted a log on the input parameters of a computer, we found that it draws around 0.6 Amps @ 0.6 PF lead !! The filter itself is a passive filter (LC combination) and hence would deliver leading KVARs. If We connect this filter at the input of computer, will it damage the power supply of the computer ?? Pls advise.






RE: Input Power to Computers
The L-C filter can be designed with lagging power factor. It depends if Xc=1/(2pifC) is smaller or greater than Xl=2pifL.
RE: Input Power to Computers
RE: Input Power to Computers
Xl>Xc
2pifL>1/(2pifC)
L>1/(4 x pi x pi x f x f x C)= 1/(4 x 3.14 x 3.14 x 50 x 50 x 36/1000000)=28.17mH
RE: Input Power to Computers
This will tune it to 158 Hz and will amplify 3rd harmonic instead of reducing it ?! I want to tune it to less than 150 Hz. !!
RE: Input Power to Computers
f=1/(2 x 3.14 x sqrt(L x C))= 1/{2 x 3.14 x sqrt[(28/1000) x (100/1000000)]}= 95Hz
for capacitance C=100microF, for example; however, the capacitance value may need some fine tuning to have the power factor acceptably high.
RE: Input Power to Computers
for xl > xc at 36 uF, the value of L is 281.7 mH and not 28.17 mH as indicated by you earlier. This is not workable. Hence there is no alternative than to use LC combination tuned to near 150 Hz, but we have to live with leading PF at the output of filter, hence pls advice what other precaution should we take to safeguard working of SMPS of computers??
RE: Input Power to Computers
C50 x L50 = 1/(2 x 3.14 x f)**2 = 1/(2 x 3.14 x 50)**2=0.000010142, in F x H
Next, L50 = 282 milliH
C50 = 0.000010142/(0.282)=36 microF
Backcheck:
2 x 3.14 x 50 x 0.282 = 88.55 > 1/(2 x 3.14 x 50 x 36/1000000) = 88.46
If you intend to keep your existing L and C values, a check for oscillation/resonances and current rms drawn by SMPS should be performed.