Quote:
Originally Posted by Army
I'd say that that idea hasn't taken off because of the whole alternator dynamo thing...
...dynamos are dependent on brushes and commutators which wear and stop doing their job - whereas alternators electrically speaking don't depend on mechanical contact.
However these days with modern electronics and some electric cars using multi-phase alternating currents from batteries (Tesla motors for example) =>
If you could reliably produce a 3 phase power supply from a car battery for long enough to start an engine and then have your induction motor behave as an alternator...
...I think you'd be onto something as typically you'd need a smaller multiphase alternating current motor / alternator for an equivalent power output from a single phase motor / alternator motor and a DC motor / dynamo set up.
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Wow that is overthinking the problem---at least from my POV.
The Starter-Generator works well in the small engine application. One component operates as both the starter, and the generator--simple is better. Typically in Garden Tractor use, these engines start once and then run for hours before being shut off and re-started, so the relitively low charge rate is not an issue. Small engines are also generally run at their full governed speed so that a generator works at the speed it needs to generate.
The problem is the mechanical points that operate the voltage limiting circuitry. They basically open and close rapidly to limit the effective charging rate to around 13 volts. Unregulated, they'd put out 18V or more which is bad for the battery. So the points close-the voltage rises. When the voltage exceeds a value set by interaction of spring pressure and electromagnetism, the point open and the voltage falls. Then they close and the voltage rises. All this happens many times a second. Its a balancing act between the spring pressure and the electromagnetism---its all mechanical.
Seems like someone should know of a solid state switching device that could produce the same result without the mechanical points.
Maybe not.