generator design

[Sarahisme]

hey all

i am interested in trying to make my own little generator (a hobby type thing).

however first i thought that i would look into some of the physics behind it. (i think faraday's law or something is involved) but i have not learnt anything in school yet about doing this kind of thing and was wondering if anyone would like to help me out a little bit with doing or designing this?

 

Cheers

 

Sarah

[5614]

A basic electrical generator just has a magnet inside a coil.... either hand held or powered by a turbine.

 

But I don't think that's quite what you are asking... maybe?!?

[Sarahisme]

umm well what i was thinking is yeah rotating a coil in a magnetic field, or vica-versa, (doesnt make much of a difference does it?, whichever is easier to move i suppose)... but its all the equations and laws that i am not sure which ones of those i should be using?

[5614]

It doesn't make much of a difference no, its the relative speed you're looking for. I'm not sure if there's a difference between rotating a magnet and pulling it in and out of a coil.

 

What kind of equations are you looking for?

[RICHARDBATTY]

Just a quick thought. A rotating magnet requires no rotating contacts and will be easier to make.

[Sarahisme]

hmm yeah i guess rotating the magnet is the better option.

 

the kind of equations, i spose faraday's law of induction and magnetic flux laws, i am just not quite sure how to put them all together :S

[calbiterol]

You could attach it to a stirling engine.

 

If you want suggestions on the actual construction (which I don't think you do, seeing as you asked to the maths and principles behind it) it might be better to have this thread moved to the engineering section.

[Sarahisme]

how do i move it to the engineering section?

[calbiterol]

Email a mod and ask them to move it to the engineering section (tell them the thread name and location).

[akcapr]

a generator is just a motor that you spin. take an electric motor, spin it like with your hands, and measure the voltage coming from the electrodes.

[Sarahisme]

ok, yeah but how does the physics work behind that, i want to do both really, build and have a least a moderate understanding of what i am actually doing

[YT2095]

you don`t have to limit yourself to a rotational design, you could use a linear "Push-Pull" design also.akcapr is quite right, a permanent magnet motor will serve perfectly well as a generator (I made a small petrol gen with an electric wheelchair motor the same way). so if you can lookup how to make an electric motor (the sort you can do at home for a school science project) your on your way

the most simple types use a couple of bar magnets a large paperclip some enamelled wire and a few nails and some wood (and your little 6 volt lantern battery).

a Linear design would be a plastic tube in which fits a bar magnet on a plunger, around the outside of the tube are many windings of wire, as the magnet moves in and out of the tube, a current is induced in the wire.

 

hope that helps a little

[Sarahisme]

thanks for that YT2095, sounds interesting for the actually real-life building of it, what about on a sorta powering a small home scale, how would that be designed? in a simliar way i suppose, but with bigger components?

[5614]

Well on a national scale a power generator has, well, it varies:

 

Burning things make steam turns turbine, turbine moves magnet in a coil.... basically it's about getting a turbine to turn, be it by burning something, wind turning it, water turning... once you've got rotation it just puts that into the magnet, possibly a gear system is used to get the magnet to move faster.

[YT2095]

more or less yes

 

the one I made did 36 volts at 5 amps using a 33cc chainsaw petrol engine.

I think for homes and the like they use deisel engines and much larger generators, but you can buy the small petrol ones for a song now, they`ll do 240vac output and depending on the requirement any thing from a few amps right up to enough to run a fairground ride or two

 

oh yeah, and if you use stepper motors (the sort you find in printers) you can even have 2 or 3 or more phase output too, I made a small wind generator using one of those

[Sarahisme]

cool!

 

i gather you understand all the physics behind how all the stuff works then?

[YT2095]

the principals yes, but DO NOT make me do maths!

[Sarahisme]

lol, thats my current feeling, well i suppose i just need to know which equations i need to use and then try and work it out from there... so if anyone can give me a few to start with that'd be great!

[YT2095]

the only one I can remember is Flemings left hand rule.

 

there`s obviously alot more to it than that, but it`s a foot in the door at least

[Sarahisme]

yeah thats a start, thanks

[5614]

Well if you had an AC output you could use a transformer... although, well, in the UK mains frequency is 50Hz, I don't know if you could get to that frequency by hand only, so you may need a more industrial-style generator.

 

hmm, I've looked on google and can't find any useful formulae... I'd say buy a powerful magnet (and big!) and get a lot of low resistance (enamel maybe?) wire make a coil and try it out.

 

Powerful magnets are not cheap though, NIB (neodiyum iron boron) magnets are the most powerful permament magnets around.

 

Try these, maybe:

http://en.wikipedia.org/wiki/Magnetic_field

http://en.wikipedia.org/wiki/Coulomb%27s_law

[YT2095]

in the UK mains frequency is 50Hz' date=' I don't know if you could get to that frequency by hand only, so you may need a more industrial-style generator.

 

[/quote']

 

no, 50hz is Very easy to obtain by hand even without the use of high gearing, a simple stepper motor of 200 per rev will output a good 500hz with a finger twist, so anything below that is childs play really

[5614]

Oh, fair enough, a stepper motor, I meant litterally 'hands only'... but yes, a stepper motor would overcome the prob!

[calbiterol]

By the way, sorry - when I said email a mod, I meant private message a mod.

[Sarahisme]

ok , i accidently posted some stuff in another thread when i meant to post here....anyways

 

this is the design of my generator...