Bull. The field current, which is controlled by the voltage regulator, is not 50 amps. To think that it would take the whole alternator output to charge the field is ridiculous.

The voltage regulator senses the battery or system voltage and passes enough field current to make the alternator produce enough power to keep system voltage where it was designed to be. That should be a couple of amps at max.

Now, the ammeter, as has been discussed here repeatedly, does pass through all the current, but usually it's way less than 50 amps.

As for mechanical or solid state regulators, I am sure that there were 100+ amp alternators on trucks that were controlled by mechanical regulators.

I have found that solid state regulators keep the voltage steadier, especially at idle.

R.