The Power+ Always Requires A Neutral Line - Gamatronic POWER PLUS Technical Manual

Gamatronic Electronic Industries Ltd.
3.1.1

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.
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 3-6 on page 21 illustrates the wrong way to connect the UPS with a grounded-neutral
generator.
Figure 3-7 on page 22 illustrates an acceptable connection solution if you already have a
grounded-neutral generator.
Figure 3-8 on page 23 shows the preferred generator (neutralized, not grounded) and the
preferred connection (three-pole).
20 Power+ Technical Guide