zero maintenance brushless alternator

[Mike Arman]

> From: "PSD" <psdooley at verizon.net>
> To: <quattro at audifans.com>
> Subject: RE: zero maintenance brushless alternator

>
> An alternator is an AC generator, hence the name.

Not exactly.

> Far as this design you mention, I thought all alternators were already built
> that way.

Unfortunately, no.

   The slip ring providing current to the spinning bits is for the
> exciter voltage, not the heavy load output voltage.

Correct.

But you're close! ;-)



Distinction between an AC generator and an alternator is that alternators have an electromagnet as 
the field and are almost always three phase (six diodes in the rectifier), and AC generators have a 
permanent magnet field and are almost always single phase (one, two [rarely] or four diodes in the 
rectifier).


AC generators are found in small motorcycles, some lawn tractors, and so forth, the permanent magnet 
is mounted on the flywheel (or some similar part) and the coils are inside. A magneto is another 
flavor of AC generator. The rotating magnet on a magneto is on the inside of the coil, so it has to 
be spun faster to get any results - ask any magneto-equipped Harley rider - from a safe distance ;-)

Alternators have an electromagnet for the field (the slip rings to spinning bits for the exciter 
voltage).

The output is from the stator on both types, and the stator is the armature.


The confusion arises when people think of DC generators where the rotor is the armature (makes the 
power) and the stator (stands still) is the field (makes magnetism). On alternators and AC 
generators, the field moves (ether permanent magnet or electromagnet) and the armature stands still.

What usually happens is someone says "the part that moves" or "the part in the middle", and the 
answer is "yeah, the armature." It doesn't matter if it moves or not, the only thing that matters is 
what it does. If it makes magnetism, it is the field, if it outputs power, it is the armature. AC 
generator, DC generator, alternator, all the same.

What makes it even more fun is that when you read the technical manuals which are translated from 
Japanese or German (or even between English English and Uhmurrican English), usually by people who 
can translate to some extent but whose technical knowledge isn't as good, you get statements like 
this one: "On assembly, make sure the gears are in harmony softly."

That's from a 1965 Yamaha manual, after some thought, I realized they were telling me not to try to 
close the crankcase halves unless the gears were properly meshed. Cherry blossoms and kimonos 
optional . . .

The point of the slip-ring-and-brushless alternator is that it doesn't need the slip rings and 
brushes to get power to the field ("exciter"), the rotating "claw plates" spin the magnetic field 
instead of requiring the actual field coil to rotate.

With best regards,

Mike Arman

50' by 90' hangar just FULL of electrical crap (and cars and motorcycles and airplanes and tube hifi 
gear and computer stuff, and I get away with it by telling my wife she has the world's largest shoe 
closet, second only to Imelda Marcos'.)