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

C O GECAN, M CHINDRIŞ, R BINDIU
into dc voltage. The conversion process
introduce in the ac network harmonics
which have different negative effects
(currents in the null conductor, inadequate
protection functioning). Such equipment
can be supplied directly to dc voltage.
Problems occur for the electrical machine
with rotating magnetic field or other
equipment, witch, for normal functioning
need to be supplied in ac voltage. The
supply of the ac loads will be achieved
through an inverter witch can supply
directly the load or the bus where more
loads are connected.
In the context of the new worldwide
energy policy, which seeks to take
measures to produce electricity using
renewable energy sources, a low voltage dc
network can interconnect distributed
generation units. Moreover, by using
renewable energy sources can be obtained
directly dc voltage. A diagram of a LVDC
network (Low Voltage Direct Current)
witch interconects distributed generation
units is shown in Figure1.
There are Ultra Low Voltage Direct
Current Systems (ULVDC) witch are
characterized by a voltage level up to 120 V.
In practice, this system is used only in case
of electronic equipment for offices and
residential buildings.
Figure 1 LVDC network with distributed generation
units [1]
Lot of equipments have in their
composition a rectifier and a transformer
which converts and transform the ac voltage
to the dc voltage at the necessary operating
level (Figure 2a) [2]. Increasingly fewer
equipment in these buildings are subject to
operation in ac voltage.
a) b)
Figure 2 a) AC voltage Supply and b) AC and DC Voltage Supply [2]
28 Ingineria Iluminatului 2009; 11, 1: 27-34