## The interaction of LEDs and power supply systems

The integral part of each LED housing powered from the chain with 230V voltage is the power supply, which is aimed at the change of alternate voltage of electronical chain into the fixed voltage amounted for 12, 24 or 48V. Present-day power supply solutions used in LED housing are based on the typical solutions for impulse power supply. The basic advantages of such solution are low expenses, lower measurements as well as weight, and higher efficiency. Power supply gathers from the chain not the constant current but impulses of current with big content of highest harmonics, which stands for the crucial drawback. Every waveform sygnal, which is not sinusoidal may be presented as the sum of n sygnals with frequencies being a multiple of the basic frequency of this sygnal. In the powering chain, the basic frequency is equal 50Hz. The frequency of harmonic row 3 amounts for 150Hz, but row 5 amounts for 250Hz. Therefore, row harmonic n has it frequency nx50Hz.

The most important problem is that currents of higher harmonics flowing in the powering chain cause voltage spoles on the chain elements that, as a result, negatively affects the powering voltage, which may be used for the powering of other collectors. In order to realize an objective evaluation of an impact of particular collector on the chain powering, it is required to know the the spectrum of current harmonics, which allows to calculate the value of Total Harmonic Distortion coefficiend, that stands for the overall deformation coefficient. The value of THD current coefficient of LED housing amounts for 26%.

The lower the value of THD current coefficient, the lower is the level of negative influence of housing to the powering chaing. Negative affection of higher harmonics on the powering chain is:

- Overload of electroenergetic cables related to the increase of current value
- Overload of neutral wire resulted from the sum of 3 row harmonics, which sources are one phase receivers, deformation of powering voltage, which are causes of inappropriate work of sensitive receivers
- Overload of element of electroenergetic chain, for example, transformers, capacitor banks, etc..

Taking into account the above, it is required that LED housings meet requirements for receivers indicated as C class according to the standard PN-EN 61000−3−2: 2007.Electromagnetic compatibility (EMC), Part 3 – 2: Allowed levels – Allowed leveld of current harmonics emission (phasic current powering the receiver ≤ 16A).