voltage after rectifier

[freejuice]

Hi Eveyone,

More good news, the generator ( 11 inch rotor, 65 turns of 14ga wire, 9 coils with 12 N42, 1x2x.5 magnets ( 24 total for both rotors) gives an easy 25 volts DC at about 60 rpm's) Hopefully this is good, I can get quite a bit more voltage by turning it faster by hand but I dont know the rpm's I can only "guesstimate" it's around 100-130 rpm's.

What say ye the Jury?

 Is this good or does this Newbie need to go back to the drawing board??? )

 Oh, one more question, even when I use the car lamp ( 12v) after the rectifier it wants to turn harder by hand...How does this affect the generators performance when I hook up my golf cart batteries to the generator....does it turn freely until it fills the battey bank voltage up...so I guess my question is: What creates or decreases the the ability for the generator to turn freely or harder after everything is hooked up?

 I dont fully understand this interaction, I'm sure its complex, can you give it to a simpleton as myself in layman's terms,

 Thanks!

[tanner0441]

Hi

Until the speed becomes fast enough to reach battery voltage there is no load on the generator, on the otherhand a cold filament on a car lamp has a very low resistance, and I bet you like the rest of us used a headlamp bulb, so it is loaded from the word go with 50-60 Watts.

Brian.

[Flux]

What are you aiming for?

With those magnets you should be able to load something like a 10ft prop ( or a bit smaller).

25v at 60 rpm would bring you to cut in at 48v at 120 rpm. This is on the low side so you mustn't expect to use less than a 48v system.

Any load on the alternator will make it hard to turn, that is the way things work, you are converting work into electrical energy. You can't get something for nothing.

When connected to the battery there will be no load below cut in so the thing will start easily enough. Above cut in it will be loaded and the power you produce will charge the battery. It makes very little difference to the load on the thing whether the battery is flat or fully charged as the volts will only change a little bit. With a low battery the power goes into charging it and when the battery is full you just use energy making gas and heat. You need a charge controller at that point to divert the current to a resistor rather than boil the battery.

If you are aiming for 48v at 8 to 10ft then you are on the right lines if not then you had better give more details.

Flux

[freejuice]

Hi Flux and Tanner,

 Thanks again, It is getting clearer on how that load/battery/prop interation works.

 I have a charge controller ready to go, bridge rectifirer and a sizeable aluminum finned heat sink ( 8x8x4 inches) for the rectifier. I also have a nice amp meter I will add to this setup.

 I was aiming for a 12volt system. I'm wanting to make my blades for a swept area of 10 foot diameter.

 Right now my air gap between the rotors and stator are about 1/8 to 3/16 of an inch and the stator magnets are N42's ( 12 per rotor, on a 11 inch diameter rotor) 1x2x.5 inches and a stator of 9 coils,( 3 phase, star) single strand at 65 turns, ( of 14 ga wire)

 At the moment I have a small bank of 4 golf cart batteries, wired in series/parallel for 12 volts.(I want to add more batteris at a later date for more reserve power)

 The tower will ( 40-50 foot) be about 125 feet away from the batteries.  

 Any reccomendations as to getting my generator to a 12 volt system? ( are these the details you are looking for)

[Flux]

This is not going to work well at 12v. As I said it is slow for 48v. At 12v it will stall hard.

I am not sure why you came up with this winding rather than copy something known to work. It would probably be ok at 24v with Jerry connection if you can get at the star point but I can't see any easy way to adapt it to 12v unless you can still get at all the coil ends.

Flux

[freejuice]

Hi Flux what would you suggest for these magnets/rotor combination? Do you think another stator would be best, if so, what would you suggest?, I have at least 6 more pounds of 14 ga wire lying around.

[freejuice]

Hi Flux,

 I would like to add: I would like to keep it as a 12 volt system.... and using the magnets/rotors I'm currently using, I dont mind making another stator if that what it takes. Any suggestions on the number of turns or star/delta?

  The current stator has a some room between each coil...about 1/2 inch or so, I'm just adding this information if you think more turns in each coil would help.

 All the best

[Flux]

It becomes difficult to deal with 12v as the wire size gets very tricky to handle.

If you have 65 turns now you really need about 17 for 12v if you keep the thing connected in the same way.

If you have lots of that wire then one way to do it is wind with 4 wires in hand and 17 turns. That in theory occupies the same space and even if it becomes a bit messy it seems as though you have a bit of space left.

If you have committed yourself to the rectifier and it is good for over 100A then this could be the best way to go.

Dealing with 4 wires in hand is not easy and leaves you a lot of ends to clean and join but it may be easier than using less strands of thicker wire.

The other alternative is to not connect the coils in series and make 3 parallel circuits, each star connected and each feeding a 3 phase rectifier. This means lots of leads down the tower or rectifiers at the top. This would require about 50 turns per coil and it doesn't work out well with your #14.

Another method would be to wind 22 turns of 3 strands in hand, connect them in series and then use all 6 leads and jerry connect it instead of star. This again needs 6 leads down the tower or rectifiers at the top.

Whichever way you do it you will need very large connecting leads and you will have a job keeping the resistance low enough if there is any long cable run.

I don't like rectifiers up the tower but with 12v it does make the winding easier.

As you will need very heavy cables down the tower it wouldn't really be a big deal to drop down 6 or 9 more modest size ones. if you do that then you could mount the rectifier at the bottom of the tower and then run 2 heavy dc wires to the battery.

You are close to the practical limit for 12v, anything above 10ft prop is not really viable.

If you could get into the star point of your present stator I would seriously think about trying it Jerry connected at 24v. If you can't live with 24v you could at least get a decent lot of data to help with the 12v stator.

Flux

[bzrqmy]

These numbers are odd,  My stator, 70 turns of #14 cut in at 24 volts around 130 rpm, seems strange that 5 less turns is producing more voltage at half the rpm's.  You might try it at 24V since you have enough batteries to do so.

Keep us posted.

[Flux]

Interesting point. I was going on his figures. I have just looked at some figures for someone else's design and with 65 turns I got a cut in for 24v at 150 rpm .

It is probably best to sort out what is going on here before doing any changes to the stator. As you say it looks as though it ought to suit 24v and if Jerrry connected it may be reasonable at 12v.

With only 11" rotors there is little chance that changes to the construction are going to drop the speed to half. If the discs were very large it may have dropped to some extent.

My guess the rpm readings are wrong but it may be voltage measurement that is off.

Flux

[freejuice]

Thanks Flux and everyone ,

 You guys are a wealth of knowledge....thanks for putting up with me throughout all of this!

 It looks like I wound that stator for 48 volts, I will go with their listed plans of two strands of 14 ga wire to hit 12 volts, or your idea of 4 strands at 17 turns.

For some reason I want to stick with the 12 v system...why I really dont know..maybe its the fears of buying more batteries or inverters at the moment.

[Dave B]

 Lots of talk and assumptions about many things with your system but I can't find the big missing link, your blades. Blade performance is key to matching the rest of your components for a working system. You could possibly run a certain profile and diameter that will work very well for what you have already built.

 If you are following the "standard" for the battery charging axial design then sure, follow it to a "T" INCLUDING the blade profile and size and things should work out close for a comparable system. If you have already made changes to say your rotors and stator and the numbers seem different then you may have to make some adjustments.

 Your blades are a huge player in the overall design and performance of your system, get them into the picture as soon as possible and have fun experimenting and testing if need be. There is no right or wrong setup just some guidelines to get you in the ballpark if you want to follow the norm.  Dave B.