Victron "Energy Unlimited" - Utu

8.2.2. DC generators
Next to conventional 50/60 Hz AC generators, some generator suppliers are offering DC generators. DC generators are
smaller and lighter, and have a higher efficiency than AC generators. Moreover, engine rpm can be harmonised with
current demand, so that fuel efficiency remains high even under partial load.
8.2.3. Unlimited inverter power
Sinusoidal inverters have now become generally accepted.
New is the possibility to connect inverters in parallel.
Victron Energy has developed inverters and inverter-chargers (bi-directional converters) that can be parallel connected in
either single or three-phase configuration.
The parallelable inverter/ charger modules are the Multi 12/2500/120 and Multi 24/3000/70, which have a continuous
output power of 2 kW at 12 V input and 2.5 kW at 24 V input respectively.
Up to 6 modules can be connected in parallel per phase. Taking as an example the 24 V model, the output power which
can be reached is as follows:
Single phase Continuous output P30 Maximum output
6 x Multi i 24/3000 6 x 2.5 = 15 kW 8kW 30 kW
Three phase Continuous output P30 Maximum output
18 x Multi 24/3000 8 x 2.5 = 45 kW 54 kW 90 kW
Where previously installation of an AC generator was a must, parallel inverters are now an
alternative.
8.3. The AC concept can be improved with PowerControl
8.3.1. The AC concept
In the AC concept one or more petrol or diesel fuel-powered generators are the hart of the system.
Whenever AC power is needed a generator is started. The generator has to be rated to meet the highest power demand
that is expected.
In general the generator, together with a battery charger, is also used to charge one or more small service batteries for
navigation equipment, lighting, DC pumps, etc.
Likewise, shore power has to be rated to meet the highest power demand that is expected. Shore power must also
match the frequency and voltage of the on-board AC equipment. If not, a frequency converter (also called shore
converter) is needed.
The AC concept is the preferred solution when a lot of power is required.
8.3.2. The AC concept with generator free period
As power demand decreases, the drawbacks of the AC concept become more and more prominent. The generator will
operate without any load at all for long periods of time, or will have to be started and stopped frequently, often operating
with hardly any load. This of course means noise, pollution, fuel consumption, wear and maintenance while at same time,
on average, electric power consumption is low.
A way to improve on this situation is the generator free period, which requires in addition to the generator a big battery,
battery chargers and inverters. When the generator is off, all consumers are supplied with energy stored in the
battery. Periodically, in general when a lot of AC power is required anyway, the generator is started and then also used to
recharge the battery.
Although much better than the “generator only” concept, there still is a lot of room for further improvement.
This is the subject of the next sections.
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