ingineria iluminatului - Journal of Lighting Engineering - Prof. Florin ...

Moreover, most of new electronic
equipment have in their composition a
transformer followed by a rectifier. The
transformer is supplied even when the
equipment is in stand-by, therefore, losses
occur during the period the equipment is not
on. One solution proposed for dc and ac
voltage distribution is shown in Figure 2b [2].
By waiving the process of conversion
and use a scheme such as that proposed in
Figure 2b, the number of converters is
reduced compared with the classical
solution and when the power losses of the
electronic equipment are also reduced.
Basically, only one rectifier in needed,
located before the dc bus; power sensitive
loads can be supplied also through a battery
storage.
LVDC networks presents several
advantages:
- safety: for human body the dc voltage is
not as hazardous as the ac voltage
because it dosen't leads to involuntary
muscle contractions. The dc voltage
must be less than 50 V to avoid this
danger to the human body. Moreover, by
choosing for the voltage level a
sufficiently small value, a completely
safe system may be realized in this
regard;
- magnetic fields are reduced;
- since for the whole system just one
rectifier is needed, we can chose a better
quality one (a IGBT based converter) in
witch case with a proper control, the
impact of electronic equipment in the ac
network can be reduced by lowering the
harmonic content;
- a converter that allows a bidirectional
flow can introduce energy into the ac
DC Voltage lighting systems
network when there is a surplus
produced in the dc network due to the
existence of an increased potential of
renewable energy.
3 AC and DC low voltage hibrid systems
Most applications of dc voltage in
residential and office buildings occurred as
a result of developement in technologies
used to produce electricity using renewable
sources. Using photovoltaic modules admits
dc voltage production. To avoid some
conversion processes witch are carried out
with a specific performance, questions arise
regarding the use of direct current for
various suitable applications.
Although recently technical
developments in this area are significant,
although there is real potential for such a
system to provide energy to a whole facility
often a hybrid solution is chosen. There are
high power loads (washing machine, air
conditioning unit) witch have to be supplied
in ac voltage for normal operation. For this
reason, in most cases a hybrid energy
supply sistem is accomplished (ac and dc
low voltage system). Such a system can
interconnect the renewable energy sources
and allows energy storage in the batterie.
Figure 3 presents a simple hybrid system.
4 DC Lighting sources [4]
Lighting is a popular use for renewable
energy. There are several methods to
achieve a lighting system using dc voltage
and establishing the best solution is quite
easy even for particular requirements.
Ingineria Iluminatului 2009; 11, 1: 27-34 29