Model generator build from scratch

[Steamchick]

Please can you post details of magnets - plus supplier?
I am sure I am not the only curious watcher here.
K2

 

[darwenguy]

Hi im not sure if you read my post there? I have stated the amps at set voltages?
Is this wrong?
I used a multi meater to measure amps, i presume this puts the load on the generator as it certainly is noticable when testing.
I used the cheep digital display for demonstation as i just dont have enougth hands to use the multimeater and camera together.
Also yes using iron in the stator would increases performance up to about 25 percent but not much more at all.
At least ive proven all no nay sayers from earlier on saying irin must be used lol.
Best regards.
Luke.

 

[darwenguy]

Magents are as stated in post and frome ebay, i think they label them as n52.

 

[Steamchick]

On Magnets, All I have seen is "Ive now got some bigger magnets to try also these are 25x10x3 and much much more powerfull and also cheeper!"
Maybe you have an ebay reference number? I have bought too many things and got the wrong ones because I wasn't so specific on E&@y. The supplier and a reference usually nails it.
On Voltage and current - sorry I missed that. - Somehow there are a load of posts I haven't read? a lot of pictures I had not seen? - I guess they were lost in the ether?
Now looking at the 12V x 1.8A I would have expected a similar sized motorcycle alternator to produce 10Amps at 3000rpm, but around 3 ~4 amps at 1000rpm. But with old "steel" magnets, not modern rare earth magnets. - This with a 0.004" air gap between rotor and stator poles. So maybe this difference is due to the number of windings, or the iron core in the motorcycle alternator? Remember Voltage proportional to rotor speed, but Current proportional to field strength and number of windings. Current LIMIT is based on wire size.
Sorry about my missed stuff, but I am only trying to help you work out a good design. I do accept the command from the "Go away" button if you wish me to do so. (You won't be the first to say that).
Regards,
K2

 

[Steamchick]

Crazy computer!
It has just changed your post #62 by adding a paragraph about Iron and added post #63!
I flippin give-up....
K2

 

[darwenguy]

Yes the magnets are 25x10x3mm n52 rare earth il use whoever selling them cheepest on the internet.

 

[darwenguy]

Hi all, managed to get some casting of the parts done this morning. The patterns all pulled realy nice, the molds are just cooling down and we can see how they turned out after dinner
Also this melt was mostly recycled car alternator housing so very fitting i think.

Il update this evening.
Best regards.
Luke.

 

[BaronJ]

An observation on your test rig. The Orange stator looks like some Nylon or other non-magnetic material. "Of course" (an electrical engineer would say) you need an iron core to get to "practical" magnetic circuits so the magnetic field strength is much higher and the voltage and current will consequently rise.
Maxwell explained it all in the 1870s and wrote the text book still in use today. I'm not an Electrical engineer so won't try and explain. I'd have to read the book - but I suggest you do instead? Or the others on this thread?
Something to do with B=nI, dB/dT proportional to V? etc.
Cheers!
K2

Basically you need a conductor for the magnetic flux to link the coils !

 

[Steamchick]

Yes the magnets are 25x10x3mm n52 rare earth il use whoever selling them cheepest on the internet.

Thanks -the Na2 is the useful bit. I shall be ordering different dimensions anyway.
Cheers!
K2

 

[Steamchick]

For spell-check's Na2 read N52 - which is what I typed.

 

[darwenguy]

No problem steam chick,
Excuse my short replys but i only use this via my phone and it takes too long.
I think you can answer most of your questions if you read my posts.
Best regards.

 

[darwenguy]

Just have a look for nedimium magnets they come in pretty much any size you want. This is still a work in progress so nothing set in stone yet

 

[darwenguy]

Basically you need a conductor for the magnetic flux to link the coils !

Why is this?

 

[Richard Hed]

On Magnets, All I have seen is "Ive now got some bigger magnets to try also these are 25x10x3 and much much more powerfull and also cheeper!"
Maybe you have an ebay reference number? I have bought too many things and got the wrong ones because I wasn't so specific on E&@y. The supplier and a reference usually nails it.
On Voltage and current - sorry I missed that. - Somehow there are a load of posts I haven't read? a lot of pictures I had not seen? - I guess they were lost in the ether?
Now looking at the 12V x 1.8A I would have expected a similar sized motorcycle alternator to produce 10Amps at 3000rpm, but around 3 ~4 amps at 1000rpm. But with old "steel" magnets, not modern rare earth magnets. - This with a 0.004" air gap between rotor and stator poles. So maybe this difference is due to the number of windings, or the iron core in the motorcycle alternator? Remember Voltage proportional to rotor speed, but Current proportional to field strength and number of windings. Current LIMIT is based on wire size.
Sorry about my missed stuff, but I am only trying to help you work out a good design. I do accept the command from the "Go away" button if you wish me to do so. (You won't be the first to say that).
Regards,
K2

OK, GO AWAY! But before you do, does you know if one can build a generator in which the coils are NOT in series? Series just doesn't seem right to me but I have never workt with building generators.

 

[darwenguy]

OK, GO AWAY! But before you do, does you know if one can build a generator in which the coils are NOT in series? Series just doesn't seem right to me but I have never workt with building generators.

This is wired in single phase, just two terminal ends to deal with. It could also be done in three phase with a different rotor config.

 

[Steamchick]

Series coils are needed on "slow" generators to add the coil voltages to get the usable total voltage. But limited by wire size for current.
Where a generator is driven "fast enough" to achieve output voltage at a useful engine speed, coils are connected in parallel to increase the current without getting too high a generator voltage at "over-speeds".
A bit of "mix-and-match"...
Cheers!
K2

 

[darwenguy]

Hi all, so i got some decent castings all fettled and ready to machine in the morning now, actually already started on the rotor. I should have the first model finished by next week.
Il do another test when its finished now, il have to get some 12v car bulbs to show you as i only have 12v leds and it blows them in seconds as soon as it goes over 500rpm.

 

[awake]

Looks like some really good castings! And a very interesting project.

 

[BaronJ]

Why is this?

If you consider your magnet passing the coil, one side is going to produce a unidirectional voltage which will get reversed as the magnet passes the other side of the coil. This produces the alternating voltage that you see.

By linking the coils with an iron frame the coils will see a second magnetic field from the produced voltage which will reinforce the one that the magnet produces. Effectively using the the magnetic field created by the induced coil voltage plus the one from the rotating magnets.

Essentially the transformer effect.

 

[darwenguy]

Yes but why do you say it 'needs' a iron stator? This is not true.
What you mean is an iron stator will 'increase' performance.
You need to think more homemade windmill generator type, they use mostly perspex and plywood stator housings and just rely on the magnetic flux to induce the coils.
Think as simple as holding a coil in one hand and a magnet in the other and waving them next to each other, a electric current is produced regardless of being near iron.
Ive already shown a working generator made just from plastic.
Best regards.
Luke