Are you dealing with motorcycle ignition/battery charger? Because some
motorcycles work exactly the way you are suggesting.

You should expect some heat, but because the magneto can only supply a
limited current under short-circuit condition, if you use the right
transistor (some motorcycles use Thyristors - they stay on until the
current drops to a minimum) and diodes, everything should be OK.

Isaac


Em 30/11/2013 08:02, Electron escreveu:
> Hi!
> I'd like to ask a theoretical question: a magneto is substantially
> an AC source + an inductance.
>
> What happens if I short it (via a transistor)?
>
> Is there power (heat!) produced during the short?
>
> Is the magneto and/or the transistor really loaded?
>
> e.g. if the transistor can withstand max 1A, I guess this limit
> must not be passed, right?
>
> I ask because the transistor seems cool although it's shorting a
> power source.. so I don't understand if the inductance of the magneto
> does effectively change things versus a more easily understandable
> circuit without inductance.
>
> i.e. I suspect that no power is consumed if I short the magneto, so
> the components aren't stressed, but I'm not really sure.
>
> Hence I ask the experts here. ;)
>
> What I'd really like to do is to limit the tension on a capacitor
> charged by a magneto, but I only have access to the magneto's wires,
> and only in parallel. No exception to this is possible (e.g. to
> interrupt the circuit in series).
>
> So my idea was to monitor the tension on the magneto itself (as it
> will be limited by the capacitor anyway, through the diode), and
> once the maximum voltage that I want to allow is reached, to short
> it (PIC software manages everything) and start monitoring current,
> and release the short when current reachs zero (to avoid a boost
> effect).
>
> But will the shorting overstress the magneto?
>
> Cheers,
> Mario
>

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