Ratings of Harmonic Filter

To size the harmonic filter, you need to identify the harmonic sources.

Then you need to check the harmonic contributions from each of the sources.

which will give you the clear idea about the harmonic order which is dominant in the system.

based on that you can select the corressponding harmonic filter, also check whether you need pf factor improvement in addition to the harmonic mitigation.

then you can select harmonic cum pf filters for your application.

you can ask the UPS supplier to give the harmonic details,

you can also ask UPS supplier to use internal 3 winding transformer and harmonic filters if UPS is still not ordered which the best way to control the harmonic at the source end.

thanks, but need thumb rule if any in selecting harmonic filter

There is no thumb rule as such. The subject of Harmonics itself is quite a complex one and requires accurate measurement and analysis by Experts and Certified professionals. Measurements need to be carried out at various critical points, feeders, transformers etc. The study is the first step in the direction of mitigating the harmonics problem. The next step is proper designing of the filters as per the requirement. Cheers, RV www.econserve.in

it better to ask UPS supplier to provide the inbuilt filters inside the UPS

Thumb Rule??? That too for such a complex phenomenon called "harmonics". I am really scared.

I advise that you take up a power quality study of your installation, fing out the dominant harmonics then decide the filter.

Remember that as with any filtering scheme, the harmonics current (ITHD) will only be reduced upstream of the filter. The harmonics current (ITHD) will not change by much between the load and the filter connection. This is because the harmonic current cancelling is done where the filter current "meets" the load current. Depending on where you connect your filter, it might not reduce the harmonics current in the bus-work.

This is in contrast with the harmonics voltage (VTHD) will be reduced on all the power feeder.

Thanks for all suggestions. Problem with me that harmonic filter is coming inbulit with the UPS. Even though the consultant is asking for it. All loads are through tapp-offs breaker of Busduct and it is very tough to put the harmonic filter at each load point(11 tap-offs points for each run,total 6 runs) Type of loads are computers. i have a solution guys but i dont know wether ir will work or not,to get the ratings of harmonic filter installed in UPS and using this same filter at source point of Busduct. please suggest. thanks Aamir

Please, send a single line diagram. Your description is not obvious.

if ups having in built filter justify to the consultant that the harmonics injection from the the UPS are reduced at the UPS end only. Give him the harmonic report

seemed i had same trouble