permanent magnet alternator for turbine

[matthew]

i have a rough understand behind how to build a permanent magnet
alternator however i still have a few questions.

1. from the home build PM alternators i've read about on the internet
most people put laminates or iron filings (in resin) behind the
coils; is this to strengthen the magnetic field? if so would
laminates or iron filings behind the magnets themselves also
strengthen the magnetic field? i've read the reason laminates are
used instead of a solid piece of steel is because eddy currents occur,
is this ture?

2. i know the magnets need to alternate North/South, but do the coils
need to be oppositely wrapped or are they all wrapped in the same
direction

3. is there a particular shape or size relative to the magnets that
the coils should be?

4. finally, about the highest output i've seen from a homemade PM
alternator is around 1 Kw, and this being a fairly large machine.
however looking at industrial produced PM alternators i can find must
smaller alternators with much higher outputs. what i'm wondering is
where is the difference? is it in the way the coils are wound, or the
magnets, or just being highly refined?

thanks for any advise
matthew

 

[Steve]

if so would
laminates or iron filings behind the magnets themselves also
strengthen the magnetic field?

Yes, by reducing the RELUCTANCE of the magnetic circuit.

i've read the reason laminates are used instead of a solid piece of steel is because eddy currents occur,
is this ture

Yes.

Have you seen this site ?
http://homepages.enterprise.net/hugh0piggott/

Lots of stuff on axial flux alternators.

4. finally, about the highest output i've seen from a homemade PM
alternator is around 1 Kw, and this being a fairly large machine.
however looking at industrial produced PM alternators i can find must
smaller alternators with much higher outputs. what i'm wondering is
where is the difference? is it in the way the coils are wound, or the
magnets, or just being highly refined?

Axial flux machines are much less efficient that radial flux machines,
but much easier to build.

Steve

 

[Kevin McMurtrie]

i have a rough understand behind how to build a permanent magnet
alternator however i still have a few questions.

1. from the home build PM alternators i've read about on the internet
most people put laminates or iron filings (in resin) behind the
coils; is this to strengthen the magnetic field? if so would
laminates or iron filings behind the magnets themselves also
strengthen the magnetic field? i've read the reason laminates are
used instead of a solid piece of steel is because eddy currents occur,
is this ture?

Yes. The iron helps gather the magnetic field. Breaking up the iron
core is to prevent the electricity from spinning though the iron the
same way you want it to spin though the wires.

2. i know the magnets need to alternate North/South, but do the coils
need to be oppositely wrapped or are they all wrapped in the same
direction

3. is there a particular shape or size relative to the magnets that
the coils should be?

It depends on how you build the motor. There is more than one way to do
it. Simple home-made generators will match each magnet to one coil.
Commercial generators avoid that because it causes vibration.

4. finally, about the highest output i've seen from a homemade PM
alternator is around 1 Kw, and this being a fairly large machine.
however looking at industrial produced PM alternators i can find must
smaller alternators with much higher outputs. what i'm wondering is
where is the difference? is it in the way the coils are wound, or the
magnets, or just being highly refined?

Industrial generators have a field coil winding that is much stronger
and heat resistant than a permanent magnet. Of course, refinement of
design helps a lot too. A car alternator is an example of a tiny
generator with 500W to 1000W output. Pick one up at a junkyard to see
how one works.

 

[N. Thornton]

Hi. The only sensible advice is dont. Home made gens are inferior in
every respect, including efficiency, reliability, robustness, noise,
and time.


Regards, NT

 

[Al]

Hi. The only sensible advice is dont. Home made gens are inferior in
every respect, including efficiency, reliability, robustness, noise,
and time.

Buy it already built and never learn anything.

Al