Simrad Maris ECDIS900, Installation Manual

Page: 57 / 64

Page 57
MARIS ECDIS900 Installation Manual
Typically, there are no supervisory circuits for battery condition.
If the power line is stable, as in your office, this type can be a candidate. When running on a
stable power line, the power goes straight through the box. It is exactly like powering your
computer from the wall outlet.
In case the power disappears, a mechanical relay will operate and connect the output to the
inverter. The inverter is started, powered from the battery, and now supplies power to the
computer.
This takes time as a mechanical relay is involved, and for a short while there is no supply to
the computer.
The question of survival is entirely up to the design of the connected computer, as the build-
in capacitors must supply power for this period. If insufficient, the computer will malfunction.
Running computers on a change-over type on ships is doomed to go wrong, because there is
no noise filtering, no protection of brownouts and no protection against drifting frequency.
Figure 1: Block diagram of a change-over type UPS.
The always-on type
The always-on type has one disadvantage – it is expensive.
That said, the rest is just what we need.
A power line with fluctuating voltage or frequency and filled with noise is not a problem. The
output is a stable sinus curve; noise free 220 Vac on 50 or 60 Hz. The UPS can even convert
(and will do) frequencies in the range 40-70 HZ to 50 or 60 Hz, depending on the setup. This is
important on ships with propeller shaft generators.
Brownouts are dealt with in the same manner, and because no mechanical parts are involved,
there will be no power interruptions whatsoever.
Supervisory circuits for battery condition and operation are standard, and the battery will
even be tested under full load periodically without any need of operator intervention.
A worn-out battery will raise acoustic and visual alarms.