# High Wattage Gas Generater?

Discussion in 'The Projects Forum' started by Monster_Magnet, Jan 18, 2009.

1. ### Monster_Magnet Thread Starter New Member

Jan 16, 2009
2
0
I have been doing quite a bit of research and have yet to find out how a gas generater outputs 10kWatts-15KWatts @ 220VAC and 120VAC. Ive found numerous schematics on building a 12VDC to 120VAC or 220VAC inverters but they all range from 300Watts to 1000Watts. Its stated many times that the 12V battery will explode if the wattage is increased any further.

My goal was to mount a 10hp-11hp horizontal shaft motor to a base structure and install a pulley to run a 65Amp internally regulated alternater. The alternater would then connect to a battery, and the inverter to supply 120VAC and 220VAC to the face where I planned on mounting the controls(Switches) and recepticles(Plugs).

If someone could explain how such a high wattage can be acheived without sacrificing the required voltages and amps to run delecate equipment I would be in your debt. This is a project Im researching as a possible senior project and was hoping to build it big enough to run a welder/plasma cutter that runs on 220VAC @ 23Amps or a small house in case of emergencies.

2. ### mik3 Senior Member

Feb 4, 2008
4,846
63
A car battery is 12V, if you draw 1000W from it the current will be 1000/12=83 Amps. A car battery will explode due to overheat if it supplies continuously such an amount of current. Also, it will drain in less than 1 hour.
You say you want to drive a 10hp motor which is about 7500W. if you use a truck battery which is 24V then the current it needs to supply will be 7500/24=312Amps. This level of current will cause problems again. You can wire many of them in parallel (which is not a very good idea) to share this current or you can combine them in series-parallel combination to increase the voltage to 48V and reduce the current. However, this will increase the cost, maintenance, weight and so on.

3. ### SgtWookie Expert

Jul 17, 2007
22,182
1,728
Let's say that your alternator will output 14v @ 65A, for 910 Watts.
910 Watts * 82% = 746.2 Watts to play with.
At 120VAC, that's 6.218A.
At 240VAC, that's 3.109A.

4. ### thingmaker3 Retired Moderator

May 16, 2005
5,072
6
Multiply the output voltage of your alternator by 65 to determine power output.

Have you considered using a bank of batteries instead of a single battery?

5. ### beenthere Retired Moderator

Apr 20, 2004
15,815
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An IC powered generator turns a shaft that moves a coil wound armature inside the field coils. A controlled current if fed into the armature through slip rings and carbon brushes so as to maintain a constant voltage output over a wide range of output current draw.

The field coil is center tapped. From the tap to either end will be 120 VAC, and end-to-end give the 240 VAC out.

That might seem to be more direct than rectifying the output and running an electrically noisy (and lossy) old inverter.

6. ### kubeek AAC Fanatic!

Sep 20, 2005
4,670
804
In my work, we use many online UPSs, I guess about 70kW each. They use stacks of 12V batteries in series, to generate 400V. This then is switched to produce 230Vac and feed the computers. This still is cca 175A when we run off batteries, but the system is only capable of cca 10 minutes of work before the batteries are empty.
For continuous use, I think you could need about the same amount of batteries for the 7.5kW.

Anyway why do you need the inverter?
And what is the gas generator, and what role it has here?

7. ### Monster_Magnet Thread Starter New Member

Jan 16, 2009
2
0
Thanks for the ideas. What if I used a squirrel cage motor from a washer or dryer to produce the AC voltage instead of a alternator?
http://www.qsl.net/ns8o/Induction_Generator.html
Would something like this be more appropriate? If it would work how can I increase the wattage?
Im not even sure if Im on the right track right now, any better ideas? Im still a newbie with practically no experience other then labs and might need some extra explaining on the theory of operation so I can grasp the concept in its entirety. Thanks for the trouble.

8. ### mik3 Senior Member

Feb 4, 2008
4,846
63
I don't like the idea of the induction motor as a generator because to keep the output voltage constant when the load varies you have to change its speed and thus changing the frequency of the supply voltage. In this way you may destroy some appliances. It is better to use a synchronous motor where you can regulate the output voltage by only changing the DC voltage applied to the rotor and without the need to vary the speed.