I have an antique motorcycle that's supposed to have a fuse in the Field wire between the "voltage regulator" and the generator. The voltage regulator does not include a current regulator like most old cars do, so the fuse is important in case of a short circuit somewhere.

What size fuse? Well, when I get the engine running, I can hook an ammeter in the Field wire. Until then...

I'm wondering if there's a general ratio between a DC generator's output (in this case 6 amps), and the current carried by the field coils.

Thanks,
Dave Hennessey

 

Probably the simplest method is to insert increasing values of fuses until the fuses stop blowing . I think automotive fuses only come a few ratings so you won't have to go through many, and they are dirt cheap anyway.