Fred O. wrote:

Here I go again. Has anyone ever considered using the alternator

as a brushless motor

to start an engine ? It would seem that a 70 amp. alternator

could get you into the

1hp. range. It would require some high current switching with

some pulley mods. but I

have been thinking about it for a single rotor engine.

Fred O.

Generator and DC motors are more or less the same but I don't

think

an alternator will work as a motor when confronted with DC.

Paul Lamar

An alternator will not run as a motor. As stated it is not a

generator.

In the alternator the alternating current produced is rectified by

the

diodes before getting out at the terminal as a direct current

voltage.

It is actually a 3 phases alternator, that is why 6 diodes are used.
The process cannot be reversed by applying a voltage at the

terminal.

The fact is that the battery 12 volts is always applied to that

terminal

and nothing happens because of the diodes that blocks a reverse

current

flow.

Rino

I should have provided more detail in my "high current switching".

Forget about the diode

rectifiers and DC for a moment. A 3 phase permanent magnet AC motor

and a 3 phase permanent

magnet alternator are identical animals. The motor drives from a 3

phase AC power source,

the alternator generates 3 phase AC power when driven. With the

addition of an angle sensor

for commutation information and some high current switching

transistors one can drive a 3

phase permanent magnet alternator as a 3 phase motor from a DC source

very nicely. Right

Butch ? And all that can be done, including the switching to convert

from alternator to

starter, at less weight than a starter and solenoid. I have not

considered reliability as

yet, as I said I was just thinking about it.

Hand propping would be much simpler but I only have one hand.

Fred O.

I am sure that if you bypassed the diode package, you could have a 3 phase
synchronous motor (with DC in the rotor field). The switching package would
be a bit challenging but possible. you would probably be ahead keeping
the starter and integrating a flywheel alternator into the counter weights,
Vance J

I would like to see a schematic of how to make 3 phase AC out of DC
without a heavy transformer. A DC starter motor is 3 HP or 1.240 KW
or 200 amps at 11 volts.

Paul Lamar
 
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