capacitors connected in parallel; each capacitor is 2.2 F, provid-ing its total value equivalent to 11 F. This is for the reason oflimitation of rated voltage. The resistor previously mentioned isoptional; it is not put in our harmonic filter structure. After insert-ing the experimentally designed filter at position No. 6 of Fig. 3(b)for the case of 4 fluorescent T5 lamps with brand B electronic bal-last as an example, the current waveform without harmonic filteris less sinusoidal than that with harmonic filter as shown in Fig. 12.The first one (Fig. 12(a)) contains more harmonics than the sec-ond one (Fig. 12(b)), which is confirmed by harmonic spectrum inFig. 13. According to the results in Fig. 13, it can be clearly seen thatthe obtained harmonics level after inserting harmonic filter is sig-nificantly decreased and its reduced harmonics magnitude is lessthan the level of most orders of IEC standard; this indicates thatthe harmonic level is now conformed to the lighting equipmentstandard.Furthermore, the %THDiis improved, the obtained %THDiispresently equal to 11% (before insertion of harmonic filter, it wasequal to 23.7%) and it is lower than that of the fluorescent T8 tubelamp as shown in Table 5. The result finally shows that after insert-ing the passive harmonic filter, attenuated harmonics result is inrespect to the applied standard. This confirms the effectiveness ofthe designed filter (Table 6).