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Madgyver

Fri Feb 24 2006, 09:30PM

Registered Member #177 Joined: Wed Feb 15 2006, 02:16PM
Location: Munich, Germany
Posts: 214

kell wrote ...

You need to break it down for us. What do you need to "charge" and why do you need 720 watts of charging power? If you want to charge a battery you can use less than a tenth of the power, and should, unless you have some kind of giant forklift battery or something.

I guess he wants to charge some caps. In order to charge caps with a Mot, they must be quite large, maybe 1000J in Energy I guess?

scuba14c

Fri Feb 24 2006, 09:53PM

Registered Member #236 Joined: Wed Feb 22 2006, 09:59PM
Location:
Posts: 13

Mike, I have been working with this and know what the dangers are. I just have a rather strict dad. I was planning on powering it with a large motor, as that would be better than using a gas engine. Yes I know the power losses will be horrible from all the conversions, but there is no way around it. I'll be at college in around 6 months, so I can live with that for a while.
As for the design specs, the MOT is charging a 3.5kJ bank of electrolytics. The 6A current rating is the maximum my variac can handle. I just want to know if that much power can be produce from a smaller alternator?

Marko

Fri Feb 24 2006, 10:24PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Iy dad allows you to play with 3,5kj bank, MOT, use it for exploding, railguns, coilguns, whatever then its incredibly silly not to allow you to get close to mains.

With first you can easily get injured or killed by lots of ways, mains is almost a toy compared to this.
If you cannot use mains you should not do that kind of electronics at all.

So i dont think you are really right about all that??

Hazmatt_(The Underdog)

Fri Feb 24 2006, 11:12PM

Registered Member #135 Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735

It doesn't seem like you have any experience with a bank as large as 3.5KJ, but neither do I, and I must say, playing with HV for 10 years now, I am still shy to go near anything of the kind of energy you want to play with. My Tesla coil itself is only 1.8J!!!! compare that to a horrendous 3.5KJ shot and the differences are staggering.
The most energy I've played with is ~180J for a ring toss gun, and its still quite dangerous, can you say "Defibulator!"

All I'm trying to say is if you have to persue this, talk to some guys with experience so you don't make the one fateful mistake. Two guys that come to mind are TeslaDownUnder and Psychop.

scuba14c

Fri Feb 24 2006, 11:31PM

Registered Member #236 Joined: Wed Feb 22 2006, 09:59PM
Location:
Posts: 13

I can't use the mains because it is an older house, and he doesn't want to have to replace the wiring if something goes wrong. As far as I know that is the only reason he won't let me use it. Are Tesla and Psychop still on the forum?

ragnar

Fri Feb 24 2006, 11:33PM

Registered Member #63 Joined: Thu Feb 09 2006, 06:18AM
Location:
Posts: 1425

Hazmatt_(The Underdog) wrote ...

can you say "Defibulator!"

Sure. "Defibrillator". =P

Marko

Sat Feb 25 2006, 12:03AM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

scuba14c wrote ...

I can't use the mains because it is an older house, and he doesn't want to have to replace the wiring if something goes wrong. As far as I know that is the only reason he won't let me use it. Are Tesla and Psychop still on the forum?

Then its no problem at all.
Use good fusing, try not to have nails instead of fuses in your house supply box and it is totally impossible to do anything iwth your instalation.
This wires usually withstand very large currents and you cannot blow 'entire house' so easily even if shorted, current usually finds 'fuse' in the circuit.

Everything must go idiotic wrong (house nor your circuit must have no fuses, wiring must be ultra poor and with lots of luck you wont have to replace instalations, fire will consume that house.

You can connect mot and variac with no problems to mains, and just use fast fuse with rating lesser than your house fuse, if you short something it will blow and period.

If you want to short it a lot use isolation transformer (not too big) two small low voltage transformers with connected secondaries are also good idea.
I use such isolation, it makes thing safer (you must take both output leads to be socked) and limits current, you cannot do anything to your mains with such setup.

Hardly enough for MOT but for small stuff very useful.

Just use fuse and current limiting on you MOT and there is really nothing more to bother with here.

Mike

Sat Feb 25 2006, 02:02AM

Registered Member #58 Joined: Thu Feb 09 2006, 05:40AM
Location: Tri-Cities, Washington, US
Posts: 317

Hmm, I know what you mean though, My house is pretty old and contains crappy aluminum wire that would melt or burnup pretty easily, though i really doubt it happening

Steve Conner

Sat Feb 25 2006, 11:27AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

If your dad is worried about the wiring: Do you use an electric heater in the house? Take it and connect it in series with the mains input to your setup. Then, it's a mathematical fact that you can't possibly do more damage to the wiring than the electric heater would have done on its own, unless Ohm's Law isn't working that day.

stop4stuff

Sat Feb 25 2006, 11:58AM

Registered Member #64 Joined: Thu Feb 09 2006, 06:25AM
Location: Southampton, UK
Posts: 68

Something like this plug in RCD would protect your house wiring. I used to use a similar one when troublshooting & repairing microwave ovens.

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