----- Original Message -----
From: Don Saxby <dsaxby@...>
To: Wind Power group <awea-wind-home@egroups.com>
Sent: Sunday, April 04, 1999 9:31 PM
Subject: [a-w-h] PM Alternator design



>I am trying to build a PM alternator and need some help with a problem I am
>having.
>
>The alternator has an aluminium rotor with 24 round neo magnets 10mm dia
>spaced evenly around the circumference. To test the output I have wound 200
>turns of wire around a U laminated core. The U core then straddles the
>rotor with the poles of each magnet passing between the ends of the U.

>Can anyone out there tell me where I am going wrong.

>Don Saxby


Hello, Don,
I'm not a PMG expert, although there are individuals on this list who are
and have given quite extensive explanations to previous questions. Building
a PMG from scratch is a major undertaking and may take you several
iterations to achieve success, thus making it a hobby! I believe you need a
magnet can made of a ferrous material to complete the magnetic path. The
magnets need to provide, with the can, a complete magnetic circuit to the
windings. Aluminum is non-ferrous and inserts an unwanted "air gap" in your
magnetic path which dramatically reduces the available flux. I'm enclosing
an excerpt from one of several excellent postings by Hugh Piggott. This one
is available at;
http://csf.colorado.edu/archive/1999/energy/msg00113.html

"Like poles (which repel each other) must be placed in a row, lengthwise
along the machine. Poles face inward. Each magnet also has a pole facing
outward. There is never a north pole without a south. You also need a piece
of iron or steel tube around the whole thing to carry the field from one
magnet to the next."

Hugh is one of our resident experts and I encourage you to review his and
other's previous postings to this list. I feel their voiced experience is
your best lever to get up to speed in your endeavor! Best Luck!

Brent Peterson





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