Salicru SLC CUBE 4 7.5 kVA Mode D'emploi page 87

Fig. 11. SLC CUBE4 UPS block diagram.
4.4.2. Rectifier-booster.
The rectifier-booster has the double function of:
Converting (rectify) the alternating voltage (AC) into direct
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voltage (DC) in normal mode (input network voltage present),
voltage required at the inverter input.
Adapting (boost) the battery voltage (DC) to the required direct
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voltage (DC) at the inverter input.
This direct voltage generated by the rectifier-booster (supplied to
the inverter) will be referred to as direct bus voltage.
The rectifier-booster has a static switch at the input, using thyris-
tors, which allows the input source, alternate network or batteries,
to be selected at all times, according to the UPS operating mode.
The rectification-boosting stage is carried out by the 3 sets of dual
boost converters, one per phase, made up of a power inductor,
IGBT transistors, diodes and electrolytic capacitors for filtering
the bus voltage. The excitation of the IGBT transistors via PWM,
controlled digitally, is carried out by one of the floating-point DSPs,
with the aim of obtaining:
Sinusoidal current absorption (low THDi) in normal or AC mode,
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so that no distortion is added to the input network, avoiding
affecting the other loads.
Power factor 1 from very low levels of output load.
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Balanced absorption of the three-phase input currents.
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Direct current absorption in battery or DC mode.
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The sizing of the rectifier will allow the inverter to be permanently
supplied with 100% load, plus the power required to charge the
batteries.
4.4.3. Inverter.
The inverter converts the DC voltage present at the DC bus into AC
alternating voltage, stabilised in amplitude and frequency. There-
fore, it completes the double conversion, so that this new "clean"
AC voltage is independent of the input voltage (isolated from po-
tential disturbances, peaks, dips, unstable frequency, etc.).
USER MANUAL
The architecture of this converter is based on 3 separate single-
phase inverters with 3 switching levels (4 IGBT transistors per
phase), thus achieving the following:
Minimal switching losses (half the PWM voltage compared to
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a conventional 2-level inverter).
A reduction of the switching ripple on the power inductor, and
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an overall reduction of the L-C filtering effort.
The switching frequency is raised to non-audible values.
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The control of this inverter is also digital, and is carried out by
another of the system's floating-point DSP cores. The generated
voltage has:
Low harmonic voltage distortion (THDv), even for highly dis-
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torting loads (non-linear load).
Stable output voltage, with accuracies greater than 0.5% with
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regards to voltage and greater than 0.05% with regards to fre-
quency.
Current limit: in the event of output short circuits, starting
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loads with peak overcurrent ("in-rush"), or similar. The inverter
limits the output current by reducing the output voltage (at the
limit, to 0 V in the case of short circuits), in order to protect the
unit in such situations, or it allows "starting" loads with this
initial overcurrent.
The inverter is sized to operate permanently loaded at 100%, and
also for temporary overloads, depending on a Load-Time curve,
with typical values of 125% for 10 minutes, 150% for 1 minute.
4.4.4. Batteries and battery charger.
The batteries are the element that allows the UPS to work in the
absence of an AC input network, i.e. in autonomy or battery mode.
These elements can be integrated in the standard cabinet of the
UPS or in an external cabinet or rack (a combination of internal and
external batteries is also an option). The number of batteries (nor-
mally in 12 V blocks) must be enough to allow the rectifier-booster
to work within its operating ranges, with a certain amount of flex-
ibility to adjust to the required autonomy.
SLC CUBE4 7,5 kVA a 20 kVA - UNINTERRUPTIBLE POWER SOIRCE (UPS)-
87