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@guest said:

hello jim…im an electrical eng student…

i’m studyingthe cause of the overheating of equipment at a factory in the philippines.

Do we just divide the total current capacity of the LVSG by 2 to determine the model of the AFH to be installed… can u explain why.Current THD = Phase A = 972.5 x 26.9% = 261.60 Amperes

Phase B = 1051.3 x 25.1% = 263.87 Amperes

Phase C = 1001.2 x 26.2% = 262.31 AmperesMinimum Required AHF Capacity = Max. Current THD = 264 Amperes

Recommended AHF Capacity = 300 AmperesRecommended Total AHF Capacity for LVSG1A = 600 Amperes

Sir can you tell me why the recommended total capacity is 600 A…

Can you give me a good reference how active harmonic filters work… I cant understand how AHF produce the opposite needed current… where does the current came from. From other source? Is it better than a passive filter?

I need help from people who are knowledgeable in this topic.. help me. Thanks

I have more data… just tell me if the above is insufficient.

Hy Francis,

This is M R Srinivas, am replying on behalf of Jim Johnson (as we work in same organization).

First of all, the harmonic current in each phase is below 300Amps, hence 300Amps AHF will be okay. As 300A, AHF can generate 300A of harmonic current in each phase.

However, I understand that the LVSG is divided into two, does it mean you have two LVSG, and in each LVSG the harmonic current is about 260Amps/phase ? please clarify.

Yes, the busbar/cables/circuit breakers will over heat due to skin effect. Rotating machines such as Induction motors & Alternators will consume more power or fuel for a given load due to negative sequence harmonics.

The passive filter if designed properly will work, but there are many limitation of passive filters.

Please share us your email ID, will email few PPT’s that explains the effects of harmonics.

Best regards,