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scuba14c

Fri Feb 24 2006, 12:08AM

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

I need an alternator to power a charging system. It needs to produce 120V at 6A. The charger is a variac connected to a MOT. It was designed to be plugged in, but my parents have said I can't, so I need an alternator. I am leaning towards a permanent magnet design, but am not sure one could produce what I need. Can anyone give me any idea of the feasability of this actually working?

skmetal7

Fri Feb 24 2006, 01:29AM

Registered Member #101 Joined: Thu Feb 09 2006, 08:12PM
Location: Wisconsin
Posts: 41

well, how are you going to power the alternator? you would have to connect it to a motor, and somehow power that, possibly by plugging it in. (theres a loophole for ya!), u could power it from an engine, but gas isn't cheap. you would need a pretty strong motor, which would use several amps.

so essentially you are powering something to power something to charge something to power something!

By the way, MOTs are pretty dangerous, what are you powering with it? more info is needed

Hazmatt_(The Underdog)

Fri Feb 24 2006, 02:26AM

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

Okay, plugging in is not allowed. Motor-generator is great, but expensive in some ways.

What you may have to consider is doing something very difficult but not as expensive in 'some' ways, which is build an inverter. The battery is expensive unless you have an 18AH lead acid lying around, a 12V-120V 500VA transformer (very large and seldom available)
a bag full of 2N3055's and a lot of patience.
I know if you ask questions 'the right way' or even in a private message, some of the guys may be willing to help you design a rather powerful inverter.

Just my thoughts.

Matt

Mike

Fri Feb 24 2006, 04:06AM

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

If your that young that your parents aren't letting you plug in your MOT, probably shouldnt be playing with something that can easily kill you. Maybe convince them to let you play with some flybacks, just always use some long chicken stick device, and always show them you can practice safe procedures.

stop4stuff

Fri Feb 24 2006, 07:20AM

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

scuba,

Permanent magnet alternators are the core of many homebrew generating systems, see Fieldlines .

For your requirements, 720W a PM alt could be built, however you'd need access to welding and cutting equipment to build the alt. A simpler solution may be a petrol (gas) generator... you'd still have to 'plug' your charging system in tho.

Bear in mind that 120v @ 6A is the same no matter what the source is, and safety issues remain the same.

What is it you're wanting to charge?

paul

Steve Conner

Fri Feb 24 2006, 11:10AM

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

Haha, EV forgot to include a disclaimer on his last post:

"4hv.org accepts no responsibility for anything awful that might happen to you while your parents are out"

the_anomaly

Fri Feb 24 2006, 03:23PM

Registered Member #19 Joined: Thu Feb 02 2006, 03:19PM
Location: Jacksonville, FL
Posts: 168

I didn't think 4hv was responsible for anyone is it? Maybe if you had one of those exercise bikes and hooked it up and pedaled really fast you could get 120volts. I found this site alternator info which might provide some help. The way I got "around" my parents was to wire something successfully and then show them it work and then explain that itâ€™s plugged in the wall. If you get the alternator to successfully accomplish its task show it to your folks and then maybe they will let you build projects off the mains.

Dr. Shark

Fri Feb 24 2006, 03:37PM

Registered Member #75 Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711

4hv probably is not, but I suppose that members who give someone information that gets him killed could easily get into legal trouble, especially on the other side of the pond.
Why is this thread not locked?

Steve Conner

Fri Feb 24 2006, 04:06PM

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

If it doesn't do anything useful or interesting soon, it probably will be. Getting back to the original topic: Probably the best thing you can do is start with a few less dangerous projects. If you demonstrate to your parents that you know what you're doing, they might feel better about letting you plug things into the wall.

kell

Fri Feb 24 2006, 06:45PM

Registered Member #142 Joined: Sat Feb 11 2006, 01:19PM
Location:
Posts: 102

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.

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