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Tecnoware Power Systems
3.4.1.1 INDIRECT POWER SUPPLY
TRANSFORMER
If you are using a system input isolation transformer this will reduce distortion effects and
stop its diffusion in the system. Therefore, apart from decreasing harmonic disturbance you
can also probably avoid oversizing the power supply line.
GENERATOR
Particular attention must be paid when sizing a possible input power unit; this has high
output impedance, which is defined on the rating plate as subtransient reactance of the
alternator. This parameter makes a negligible harmonic current distortion become a seriously
disturbing element for the correct functioning of the U.P.S.
3.4.1.2 INPUT WIRE SIZING
When choosing the wire you must bear in mind a technical, economical and safety
evaluation. Technically speaking, the main factors that affect wire sizing are voltage, current,
overcurrent, temperature and how the wires are laid. However, it is always a good rule to size
the wires so as the voltage drop on each wire is below 3% of the applied voltage. Particularly
important is the sizing of the neutral wire especially when the U.P.S. is used to power
unbalanced loads or loads with strong harmonic distortion. Taking into account these last
remarks, the enlargement factor must be decided according to the size of the phase wire
(usually 1,5-2 times).
3.4.1.3 PROTECTION OF THE U.P.S. OUTPUT LINE
The main electric distribution systems to which the U.P.S. can be connected are the TN-S
and TT systems (pictures 14 and 15). If you do not have this type of equipment please talk to
a specialized technician. The protection devices, which can be applied to the U.P.S. output line,
are against overcurrent and are differential. As for their size, please bear in mind that if there
is a power shortage the U.P.S. works on its own (disconnected from the main line), with a
current restriction equal to 150% of the rated current, therefore in order to protect against
overcurrent you must choose a device that is activated within this threshold. As for differential
protections you must use type A differentials (for alternate current and for switches with
continuous components), which are low sensitivity (0,3–0,5-1 A).
EVO STAR 10-50
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