Salicru SLC CUBE 3+ PS Mode D'emploi page 109

4.4. OPERATING PRINCIPLE OF AN
EQUIPMENT.
The SLC CUBE3+ PS series UPS is an AC/DC, DC/AC double
conversion system with sinusoidal output that provides safe
protection in extreme power supply conditions (voltage variations,
frequency, electrical noise, cuts and micro-cuts, etc.). .), and
which, in addition, incorporates the functionality of trimming load
consumption peaks ("Peak Shaving"). Whatever the type of load to
be protected, this equipment is prepared to ensure the quality and
continuity of the electrical supply.
The use of technology without transformers allows a significant
reduction in weight and volume of the equipment, drastically
improving important coefficients such as the power/occupied area
ratio.
Basically its operation is as follows:
The rectifier, a three-phase bridge to IGBTs, converts AC
ˆ
voltage into DC absorbing a sinusoidal current (THDi <2%),
charging the batteries at constant current/voltage.
The batteries, by default Pb-Ca, supply the energy required
ˆ
by the inverter in the event of a grid failure, and for the
"Peak Shaving" functionality. The equipment can take
AGM, Gel or Ni-Cd batteries. For the latter two, the team
implements a double-level charger.
The inverter is responsible for transforming the bus voltage
ˆ
from DC to AC, providing an alternating sinusoidal output,
stabilized in voltage and frequency, suitable for powering
the loads connected to the output.
The particularity of the Peak Shaving function allows the
ˆ
necessary energy for the inverter to be obtained in part
from the rectifier (up to the established limit), and the
rest is supplied by the batteries, which act as an energy
storage system (ESS). Energy Storage System"). In this
way, the power absorbed from the network is limited,
with the double benefit of lower network consumption
(and less contracted power), and the sizing of the energy
system adjusted to average consumption, instead of the
consumption of the maximum peaks of load demand.
Whenever we are below the load demand peaks, and
always below the established input absorption limit, the
batteries will be recharged, for availability in the next peak
consumption cycle (see Fig. 27).
The basic double conversion structure is complemented by
ˆ
two new functional blocks, the static bypass switch and
the manual bypass switch.
The static bypass switch connects the output load
ˆ
directly to the bypass grid in special circumstances such
as overload or overtemperature and reconnects it back to
the inverter when normal conditions are restored. In the
SLC CUBE3+ PS equipment, the user can decide at any
time whether or not the static bypass is available (since
his connection could incur in exceeding the consigned
network power limit).
The SLC CUBE3+ PS B
ˆ
inverter and bypass blocks, thus increasing the safety of
the installation, since it allows the use of a second network
(generating set, another company, etc...).
USER'S MANUAL
version has separate lines for the
The manual bypass switch isolates the UPS from the
ˆ
network and from the loads connected to the output, in
this way maintenance operations can be carried out inside
the UPS without the need to interrupt the supply to the
loads.
Mains limit
Discharge battery
7:00 10:00
Fig. 27. Peak-shaving vs time.
4.4.1. Normal operating ().
With mains present, the rectifier converts the AC input voltage into
DC, by boosting the DC voltage to an optimal level to feed the in-
verter and battery charger.
The inverter is in charge of converting the DC bus voltage into AC
providing an alternating sinewave output, it stabilises the voltage
and frequency, ready to supply the loads connected at the output
(Fig. 25 and 26).
4.4.2. Mains fault operating ().
In case of mains fault or blackout, the battery set supplies the
needed energy to feed the inverter.
The inverter still operates normally, without noticing the lack of
mains and the back up time depends in the capacity of the battery
set only (Fig. 25 and 26).
When the battery voltage reaches the low voltage, the control
blocks the output in order to protect the batteries from being deep
discharged. When mains is restored and after the first seconds of
analysis, the UPS goes back to operate as it is described in the
previous section «4.4.1. Normal operating».
When mains is restored after a blackout, it is activated the recti-
fier soft start according to the «Walk-in Time» setting (10 sec. by
default), which later one can be set between 0 and 99 sec. by
our T.S.S., considering that figure 0 is disabled.
Also another parameter that manages the rectifier is the start up
delay «Walk-in Delay» (5 sec. by default and setable between 0
sec. and 1 h). This functionality is very useful in installations where
the UPs is supplied by a generator set and it is required to wait to
tart up till having a stabilized voltage and frequency.
Schematically, the operating is as follows:
AC mains Walk-in
 
is restored Delay
Peak Shaving
Charge battery
13:00 16:00
Rectifier soft start in ramp, for the
preset Walk-in Time
SLC CUBE3+ PS UNINTERRUMPTIBLE POWER SOURCE
109