Re: 20 vs 30 amp voltage regulator

Posted by Gerald J. on December 29, 2006 at 08:41:07 from (67.0.103.163):

In Reply to: Re: 20 vs 30 amp voltage regulator posted by John T on December 29, 2006 at 06:39:52:

And to add complication, it is possible with generator design to make it self current limiting. That was the principle of the third brush generators. The current through the third brush caused an armature reaction to the field and limits the current. Its likely that shifting the brushes from the perfect neutral position or shaping of the pole pieces can do that some too. Armature reaction is where the field from the armature current opposes that from the field poles.

But in any case its the wire in the armature and the brushes that limit the continuous current capability. That along with the temperature rating of the armature insulation. Modern insulation will handle a lot greater temperature rise, but the typical vintage tractor generator will have used the least expensive paper insulation with the lowest practical temprature rise because in those days saving copper didn't save enough money to pay for high temperature insulation. Today saving copper does pay. Look at the tiny starters even on trucks these days.

A good automotive electric shop might be able to readjust the current limit without wrecking the voltage regulation or have a far greater selection of regulators to get the right one for that 20 amp generator.

Gerald J.

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