# Disturbances Generated by Lighting Systems with LED Lamps and the Reduction in Their Impacts
## 5 Tests of LED Lamps with an Attached Two-Stage Power Supply  
Another stage of the tests was the repeated performance of measurements for the same LED lamps (described earlier), but this time, the lighting systems were modified with the introduction of a two-stage power supply. For this purpose, the UPS EVER Powerline RT 1000 was used. The results turned out to be very interesting. Their specifications are presented in Table 4.  
Current distortions were significantly reduced. The total harmonic distortion of current \(\mathit{THD_{I}}\) for LED lamp 1 was reduced to 32% (i.e., almost four times), and in the case of LED lamp 2, \(\mathit{THD_{I}}\) was reduced almost three times down to 19.7%. The initial uneven harmonic components \(h3\) and \(h5\) were significantly reduced from 88.5% and 60.4%, respectively, to 18.8% and 21.8% for the first light source. In the case of the second light source, the value of the \(h3\) component was significantly reduced from 46.4% to 10.4%, while the value of \(h5\) component increased slightly from 11% to 14.2%. Figures 12 and 13 present charts of the levels of the current higher harmonics in the system with analysed LED light sources and the two-stage power supply (marked in red). For the sake of comparison, the levels of the harmonics of the lighting system without a power supply (marked in grey) and the values permissible according to [50] (marked in blue) were added. On top of this, the percentage values of \(h3\) and \(h5\) components and the level of the \(\mathit{THD_{I}}\) were provided. \begin{table}
\begin{tabular}{c c c} \hline \hline  & **LED Lamp 1** & **LED Lamp 2** \\ \hline RMS Current \(I_{rms}\) & 56 mA & 145 mA \\ Amplitude of Current \(I_{m}\) & 104 mA & 215 mA \\ Current Crest Factor \(\mathrm{CF_{I}}\) & 1.85 & 1.48 \\ Active Power \(P\) & 11.7 W & 31.1 W \\ Reactive Power \(Q\) & 5.4 var & 12.1 var \\ Apparent Power \(S\) & 12.9 VA & 33.4 VA \\ Power Factor \(\mathit{cos}\,\mathit{op}\) & 0.91 & 0.93 \\ Power Factor \(\mathit{PF}\) & 0.86 & 0.91 \\ Total Harmonic Distortion Ratio \(\mathit{THD_{I}}\) & 32.0\% & 19.7\% \\
3 rd Current Harmonic Level \(h3\) & 18.8\% & 10.4\% \\
5 th Current Harmonic Level \(h5\) & 21.8\% & 14.2\% \\
7 th Current Harmonic Level \(h7\) & 4.3\% & 3.2\% \\
9 th Current Harmonic Level \(h9\) & 2.7\% & 3.7\% \\
11 th Current Harmonic Level \(h11\) & 3.1\% & 0.8\% \\
13 th Current Harmonic Level \(h13\) & 3.8\% & 1.5\% \\
15 th Current Harmonic Level \(h15\) & 5.9\% & 2.3\% \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Results of measurements of the electrical parameters in the two-stage power supply circuit with LED lamp 1 and LED lamp 2, respectively. The current crest factor \(CF_{I}\) in the system comprising a two-stage power supply circuit and LED lamp 1 was 1.85 and was improved in relation to the circuit without the correction circuit, where it amounted to 3.09. For the system that includes LED lamp 2, the value of \(CF_{I}\) improved from 1.97 to 1.48. Such values indicate a change in the pattern of the current signal, which can be observed by comparing Figure 3 with Figures 4 and 14 with Figure 15. The current waveforms presented in Figures 14 and 15 are distorted from the sinusoidal waveform to a lesser extent. The introduction of the two-stage power supply into the tested circuits also contributed to an improvement in the power factor \(PF\) from 0.63 to 0.86 (LED lamp 1) and from 0.88 to 0.91 (LED lamp 2). On the other hand, the power factor of the fundamental component \(cos\)\(\varphi\) did not change and amounted to 0.91 for the first light source, and 0.93 for the second one. Figure 12: Spectrum of the higher harmonics of the current drawn from the mains by the power supply with a double conversion and flowing through LED lamp 1 (at the power supply output) in reference to the permissible values according to [50].