ferrite magnets

[artv]

Hi......in the Homebrew glossary it says that ferrite mags(ceramic) are 4-5 times weaker than neo's. So I was wondering....because I've been doing some testing....can I take the readings I'm getting and just multiply by say 4.5......to give me an idea of what to expect if I were using neo's......plus I've stacked the mags three high.......but I know this does'nt make them 3x's as strong.....been searching but can't seem to find the answer........though I'm sure it's out there...........thanks in advance for any input....artv

[joestue]

yeah, the voltage will be 1/4th or whatever but because you have 4 times as many turns and therefore 16 times as much resistance the ouput power of the alternator is only 1/16th what it would be with neo's for the same losses.

however ferrites are about 1/16th the cost... its still not worth it. 10 minutes of google searching will get you a 200 page book that explains this stuff, i can't remember the title, can post it if you want later.

[Flux]

It's far from easy to do any direct comparison . Br for ferrite is under half of that for neo but what matters is the flux in the air gap. This at best can only be under half of the neo figure but relatively you need much thicker ferrite magnets for the same air gap.

Just comparing ferrite and neo of similar size in the same air gap will give very poor results for the ferrite compared with what it could give but probably it will be more of a direct comparison for what you are trying to do.

Ferrite can be used to produce fairly good alternators but they will be large and heavy in comparison with neo. The copper cost will be high and this largely offsets the lower magnet cost, this combined with the larger amount of magnet needed and the much increased weight and size for the same output makes ferrite fairly unattractive. Its only real virtue is the almost indestructible nature of it and in marine environments you don't have the same issues with corrosion as neo is prone to.

You will have a hard job predicting the output if you change to neo as the design really needs to be somewhat different for best results, dimensions and turns will be far from optimum for neo if you start with a good ferrite design.

Flux