Technical data

3 Device description
MASTERGUARD Series SIII
UPS Systems from 60 to 800 kVA
4
MKA4CAT0UKSIII/Rev. 11-11/2004/UK
3.3.2.4 Return to normal conditions
When the mains supply returns to
within tolerance limits, Series S
III will
continue to supply the load via the
conditioned line for a period of time
dependant on the direct line failure
rate (the conditioned line draws power
from the mains not the battery). When
the direct line has stabilised, Series S
III
returns to normal operation. The
battery charger automatically begins to
recharge the battery, so that maximum
autonomy is guaranteed in the
shortest possible time.
3.3.3 Maintenance bypass
If for any reason it is necessary to take
the UPS out of service for maintenance
or repair, the UPS shall be fitted with
an internal maintenance bypass switch
which enables a load transfer to a
reserve supply with no interruption to
power to the critical load. Bypass
isolation shall be complete, all
serviceable components such as
fuses, power modules etc. shall be
isolated. Transfer/retransfer of the
critical load may be accomplished by
automatic synchronisation of the UPS
to the reserve supply and paralleling
the inverter with the reserve source,
before opening or closing the bypass
switch as appropriate.
3.3.4 Operation Without Battery
If the battery is taken out of service for
maintenance, it is to be disconnected
from the rectifier/charger by means of
a switch situated in the UPS cabinet.
The UPS will continue to operate and
meet the performance criteria specified
with the exception of the stand-by
period. In such a case, the overload
performance from the conditioned line
may also be affected, depending on the
actual input voltage level.
3.4 Control and diagnostics
Control of the power electronics modules
shall be optimised in order to provide:
• optimum three-phase supply of the
load
• controlled battery charging
• minimum phase effects upon the
supply network.
By using digital signal processors
(DSP) Series S
III shall implement the
most advanced digital control.
3.4.1 Vector control
To ensure the quick and flexible
processing of measuring data, special
arithmetic algorithms shall be
implemented in DSP, rapidly
generating controlled variables as a
result. This will thus render possible
the real-time control of the inverter
electronics, resulting in obvious
advantages concerning the performance
of the power components. These
advantages will be:
• Improvement of short circuit
behaviour, as individual phases can
be more quickly controlled
•Synchronism or phase angle
precision between UPS output and
reserve supply even in the case of
a distorted mains voltage.
• High flexibility in parallel operation:
parallel blocks may be housed in
separate rooms.
Several algorithms included in the
Vector Control firmware are covered
by patents owned by MASTERGUARD
(95 P3875, 95 P3879 and 96 P3198).
3.4.2
Redundancy, preventive monitoring
In order to maximise the reliability of
the system, the control unit shall
monitor a wide number of operating
parameters for the rectifier, inverter
and battery. All vital operating
parameters, such as temperatures,
frequency and voltage stability at the
system output, load parameters and
internal system values shall be
constantly monitored and controlled
for irregularities at all times. The
system shall react automatically
before a critical situation arises either
for the UPS or the load, in order to
ensure the supply of the load even in
these difficult conditions.
3.4.3 Telediagnosis and telemonitoring
In all the above modes of operation,
the UPS may be monitored and
controlled from a remote location such
as a service centre, in order to
maintain the reliability of the system at
nominal levels. Even during complete
shutdown of the UPS, information
relating to the operating parameters
shall not be lost thanks to non volatile
RAMs, which will store the
information for up to 10 years.
This ensures that the load can be
transferred to the conditioned line
without break in supply where there is
a deviation from the selected input
power tolerance levels. If the direct
line failure rate has been outside
permitted parameters, Series S
III shall
supply the load from the conditioned
line. The battery charger supplies the
energy necessary for maintaining
maximum charge to the battery.
3.3.2.2 Inverter stop or overload
If the inverter is stopped either by the
operator or as a result of an overload,
there is no transfer to the conditioned
line and the load continues to be
supplied by the direct line. The mains
voltage and frequency values must be
within the tolerance limits specified.
In the event of an overload with a
duration in excess of the maximum
capacity specified, the load is
transferred to the conditioned line,
which will supply it for a specific time
depending on the level of overload.
In the event of an overload and an
unsuitable mains supply, Series S
III
shall transfer the load from the direct
line to the conditioned line (assuming
Series S
III was operating from the
direct line) and the inverter shall
continue to supply the critical load for
a period dependant on the degree of
the overload and the UPS features.
Visual and audio alarms alert the user
to the problem.
3.3.2.3 Emergency (due to mains
supply failure or variance beyond
tolerance limits)
If Series S
III is supplying the load via
the direct line and the mains supply
varies beyond tolerance levels
(adjustable using the software from ±
2% to +10% -8%), the load will be
transferred from the direct line to the
conditioned line. The load is powered
from the mains via the rectifier and
inverter, (provided the input mains
remains within the tolerances stated in
tables 11 and 12). Should the input
mains falls below the lower limit the
batteries shall be used to power the
load via the inverter. The user is alerted
to the battery discharge by visual and
audio alarms and the remaining
autonomy is displayed on the LCD.
During this process, it is possible to
extend the remaining autonomy by
switching off non-essential loads.
Tecnico-SIII-MG 10-11-2004 8:22 Pagina 4