armature rewinding question

[snake]

hi friend,i have an ametek 38vdc,it is rated at 1150rpm and 12amps.he cut in for it to reach 15v will be about 450rpm which will be a bit difficult without good blades design.i want to go cheap with pvc blades but reaching 450rpm in a 10 to 15 miles an hour wind is difficult.so,i have started to rewind the ametek with thicker wire and with 15 more turns so as it can reach cut in at about 200 to 250 rpm.

if ever i increase the number of turns,i will get some more volts but will i get some additional amps with some thicker wire size or will the output remain the same

i read that the output is determined by the magnetic flux but not by the wire size.is it true

thanks

[DanB]

very roughly...

if you increase the number of turns you'll reduce the cutin speed, but you'll likely need to use thinner wire so you can fit more turns in there, and resistance in the armature will go up a lot (Because you have longer length of thinner wire).

As it is, (if I'm not mistaken) the ametek is likely good for only about 50 Watts sustained output (maybe 100 but I doubt it) into a 12V system - it may peak at 3x that but it's not going to be a real powerhouse.

400 rpm cutin is not way off the mark.. for a tiny 12V machine.

Rewinding one is going to be a lot of work, into a motor that in my opinion is pretty small/limited to begin with.  

I'm not that keen on PVC blades - I think you could quickly carve a nice fast little 3-4' diameter wooden blade and get much better results and it'd possibly work well with the motor as it is now.  If you want to keep life simple and easy - you would probably do well with a 2 blade rotor on there and I expect you could carve that from a 2x4 easily.

[tecker]

That is a mean rewind connecting to the armature is a problem . Just get another one and run both in series .

[snake]

hi friends,thanks for your replies.in fact what i want from the ametek is that it produces maximum power at less rpm.initially,there was some space left for about 20 more turn to fit in in each slot.thats y i want to use some thicker wire and some more turns.if it gives at about 8amps at 12v,then i am happy because my battery is rated at 100amps at 12volts.

rewinding is a very good experience.i have rewound some other motor as well to give some more voltage.its not a pain for me since i like to learn.

i just want to raise the voltage cut in and to get some more amps.some friends out there said that they got maximum of 4 amps with an ametek 38vdc but i want to get some more by rewinding.i dont live in the us,shipping of some neodymium will cost me some bucks.thats y i want to modify a motor to get some more amps out of it

thanks

[Flux]

Some of those motors do have a bit of spare space and if you are very careful you may get a few more turns of the same size wire in. I seriously doubt that you will get more turns of thicker wire.

If you can get more turns of the same size wire in you will get a lower cut in speed and you will keep the maximum current rating. If you improve the speed match to the blades you may actually see an increase in current although you will not increase the motors capability.

If you have to wind with thinner wire then you will reduce the current carrying capability but again a better match may see more amps into the battery.

I agree with Dan that a decent 2 blade wooden prop would easily reach 400 rpm and would give you much better results but if you must use the pvc blades then you will be able to get an improvement if you can reduce the cut in speed even if it comes at a reduced maximum motor current rating. Much again depends on your local wind conditions.

Flux