G
AMATRONIC
E
LECTRONIC
I
NDUSTRIES
L
TD
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18
P+ PREMIUM 60, Installation Guide,
rel.
1.4
3.3.4
Cabling
3.3.4.1
NEUTRAL LINE
During both installation and operation of the Power +,
a neutral line must always be connected to the
UPS
. This neutral line must be connected at all times while the UPS is working and should not be
disconnected at any time.
CAUTION!
If at any time the neutral line becomes disconnected, there will be no
input or output reference voltage because the input neutral line and the output neutral
line are physically linked together. This may result in the system defining its own
reference voltage, which will be set by the load distribution between the three phases.
This can cause serious damage to the UPS.
CAUTION!
A 4-pole switching system can disconnect the neutral line.
WARNING!
If you have a
four-pole
mains-to-generator
switching system you are in
danger of having the
neutral line disconnected
when the four-pole switch is
operated. This can result in the problems described above.
To avoid these problems, we strongly recommend that, if you use a four-pole mains-to-
generator switching system, you install an isolation transformer that constantly
provides a neutral line to the UPS.
Figure 16 shows the wrong way to connect the UPS with a grounded-neutral generator.
Figure 17 shows an acceptable connection solution if you already have a grounded-neutral generator.
Figure 18 shows the preferred generator (neutralized rather than grounded) and the preferred connection
(three-pole).
