MaxPower Corp Gamatronic Power+ M100 - Manuel (Page 28)

Gamatronic Electronic Industries Ltd.
20 POWER+ 3x208 V, User Guide, Release 2.1
4.2 The Power+ always requires a neutral line
During both installation and operation of the Power +, a neutral line must always be
connected to the UPS. This neutral line shall be connected during the entire period
that the UPS is working, and shall 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. That may result in system defining its own reference
voltage, which will be set by the load distribution between the three phases. This can
result in serious damage to the UPS.
4.2.1 A 4-pole switch might disconnect the neutral line
WARNING!
If you have a mains-to-generator four-pole 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 will constantly
provide the UPS with a neutral line.
Figure 4-4
on page 21 illustrates the wrong way to connect the UPS with a
grounded-neutral generator.
Figure 4-5 on page 22 illustrates an acceptable connection solution if you already
have a grounded-neutral generator.
Figure 4-6 on page 23 shows the preferred generator (neutralized, not grounded)
and the preferred connection (three-pole).