Muller Dynamo

[yssuraxu_697]

There has been debates about core materials and now this hollow core thing makes things even more complicated. My 2 sents on the subject:

- ferrite cores can be made of dramatically dfferent materials so by using random material without knowing the specs is total gambling

-- resistivity, this is very important. MnZn ferrites usually have very low resistivity and thus prone to eddy currents. NiZn ferrites have resistivity of 4-5 orders of magnitude (!) higher

-- saturation, in general ferrites range from 300 to 500mT. I doubt that anyone succeeds saturating even 300mT ferrite but for example at 250mT it is out of efficent band (look hysteresis curve)

-- permeability, this can also vary by orders of magnitude, what is unclear - is there any advantage in using high permeability material

This is the point where hollow cores come in. I wonder... when using relatively weak generator winding and large high permeability core... does center portion help with generation at all? Or it just diverts some flux away from "core-winding interaction zone" and reduces output? On the other hand hollow core "focuses" all the flux in the "interaction zone". There surely are equations for that   Wild guess is that higher the permeability - thinner the hollow core wall can be while providing same (or more?) output?

Heres pics also about that "focusing" effect. Especially interesting when core and magnet are "offset".

[Tudi]

@yssuraxu_697: nice pics, but guiding flux does not mean more flux through coils ? What it actually gets things going is the strength of the flux ?
In Romerouk design the magnet on top of the coil could be pushing the the flux close to the rotor magnet, more concentrated flux at the end of the coil and less flux in upper part. Considering this is an oscilating circuit that should make the propagation of the coil MF more slow in the coil. Which is not a beneficial effect at all ? Why are those darn magnets in repelling mode helping at all ? When rotor PM is getting closer to the coil both the coil and the magnet on top is trying to push the rotor PM away -> bad effect. When rotor PM is trying to leave the coil the coil is trying to pull while the magnet is trying to push it ways, helping to kill the coil field = generated energy -> somewhat bad effect.

[yssuraxu_697]

@yssuraxu_697: nice pics, but guiding flux does not mean more flux through coils ? What it actually gets things going is the strength of the flux ?

And looking at the "offset" pic, in which case coil has more flux to interact with? When it sitting on object that has 4000 gauss "strength of the flux" in it or on object that has 2000 gauss in it?

[wings]

There has been debates about core materials and now this hollow core thing makes things even more complicated. My 2 sents on the subject:

- ferrite cores can be made of dramatically dfferent materials so by using random material without knowing the specs is total gambling

-- resistivity, this is very important. MnZn ferrites usually have very low resistivity and thus prone to eddy currents. NiZn ferrites have resistivity of 4-5 orders of magnitude (!) higher

-- saturation, in general ferrites range from 300 to 500mT. I doubt that anyone succeeds saturating even 300mT ferrite but for example at 250mT it is out of efficent band (look hysteresis curve)

-- permeability, this can also vary by orders of magnitude, what is unclear - is there any advantage in using high permeability material

This is the point where hollow cores come in. I wonder... when using relatively weak generator winding and large high permeability core... does center portion help with generation at all? Or it just diverts some flux away from "core-winding interaction zone" and reduces output? On the other hand hollow core "focuses" all the flux in the "interaction zone". There surely are equations for that   Wild guess is that higher the permeability - thinner the hollow core wall can be while providing same (or more?) output?

Heres pics also about that "focusing" effect. Especially interesting when core and magnet are "offset".

try a C ferrite with two coil on the vertical line you catch the the effect

[Tudi]

i'm not that pro in these stuff. As i see it the amount of flux that passes through the coil is the same over the PM move period, just at different points, with or without special core setup. In reality core does matter, so i'm probably wrong.