quad alternators vs generator

Hey everyone, I checked the prices of used 15KVA generators and they are pretty high. I need the generator to run my sound system and UV cannons (total about 12KW power). I thought about upgrading my 94 chevy vandura (g30 with the 7400 motor) with 4 hi-power alternators, and a bracket to hold them and attach them to the engine. Add to that 6 2500W stackable inverters and I can have a portable light weight and somewhat quiet generator (runs on LPG) to run my sound system. I found all the parts I need on the net but I think best will be to attach the generators to an electric clutch pulley so I can activate them when I want without running off engine power all the time. What do you think? will it be efficient to run it from the idler pulley instead of a towed 15-20KVA generator? Is there another way to produce 220V electricity like using generator parts straight on the pulley instead of driving them through (4) batteries and inverters? I think I also need to make the idle RPM higher but i'm not sure how efficient and gas consuming it will be and not sure how to do it (maybe a tune to the ecu?) Hope I chose the corrent forum for my questions:) -Noam

Use the 15kVA generators - far more efficient. (Single phase or 3-phase?) That'll only take about 20HP from your engine. Going the 12V path means heaps more losses and inefficiencies. The genny will have to be variable speed though (ie, modulated rotor) unless you want to run at constant speed (eg, 1500 or 3000 RPM (for 50Hz) etc. Then you can use normal domestic or musician amps or PA systems. Even higher Ohmage speakers (yay!) Else just series-connect all the "auto ruggedised" low-Ohmage crap. Using multiple alternators means specific design and matching (you can't just parallel gennies & alternators). Plus 12V means 10x the current of 120VAC or 20x the current of 240VAC etc (hence 10x or 20x the copper....). And then the batteries to hold up.... An AC generator has the same surge characteristics as a power station - it craps all over any static offering (ie, inverters).    Enjoy! My last similar system used a mere 4kW single-phase alternator (genny). Mind you, that was oldskool Watts.

hey oldspark, thank you for your quick reply:)

When I mentioned the 15KVA generators, I meant the big towing silenced diesel generators that are very expensive.

I already found all the parts for the inverter build like 350AMP hi-output alternators (with high current on idle speed), brackets to connect a quad setup, and also stackable synced inverters that each one connect to different battery (connected to a different generator). That way I guess that the output is more sine-wave and less interference on it (like a UPS).

From what I understand from your post, I should use AC generators (like electric motors) that will provide AC 220 voltage.

Where can I find such a generator with variable speeds?

3000RPM will be again, unefficient, because of higher fuel consumpsion (I am planning to use it just when ideling).

What protection circuits do you think that I need to connect to it? and how hard will it be to modify it to use an electric clutch pulley (the parts I found for the inverter method perfectly fit).

Excuse me for all the questions and lamme english, I do have experience in car modifications and audio modifications but I would like your opnions and suggestions here.

Thanks:)

There exit more reasonably sized generators in that output realm, or think of using 2 generators that are physically smaller 1 or audio and 1 for lighting. yes i realizes this adds more things to go wrong etc, but it may be the viable solution. Or even look for generators that can be ganged together. honestly though i have seen and operated 10k generators that were able to be lifted in and out of a pickup truck by 2 people (yes it was difficult)

If 3k RPM is too high, change the gearing. But whatever speed you chose must have enough torque (power) to drive the genny at max output. I don't know about the availability of vari-frequency rotors (it's been too long!), but I suspect they'd cost a fortune. Motors & generators like transformers tend to be tuned circuits (ie, you can't just change the resonant frequency of a lump of ferro-magnetic rotor and maintain efficiency (coolness)). Maybe see what is available for wind generators - they want constant output frequency despite rotational speed changes. (But I think some merely vary their power...???) Or go high frequency - any output frequency rectified to DC feeding the inverters - ie, a main UPS system (220VAC etc) - they usually run ~400V batteries. (Small UPSs use lower voltages - 12V, 24V, 48V, 96V etc, but 15kVA will probably use the full DC/peak voltage.) Maybe an army-surplus aircraft. Commercial aviation used 400Kz....

Hi again, I think you are right. 2 small generators if no room or 1 big (15000). I researched and found some examples like: http://www.northerntool.com/shop/tools/product_8795_8795 or a 3 phase (Is 3 phase more efficient?). http://www.3phasegenerator.org/3phasegeneratorhead.htm What you think is best way connecting it to the engine?