Re: 20 vs 30 amp voltage regulator

Posted by Gerald J. on December 28, 2006 at 23:04:10 from (67.0.97.190):

In Reply to: Re: 20 vs 30 amp voltage regulator posted by John T on December 28, 2006 at 18:35:02:

It isn't so much the field current but the armature current. The three unit voltage regulator has a current regulator section that limits the field excitation if the armature current gets above the regulator rating. I'm sure that any regulator with a current rating has that current limiting element.

Running a wire (like those in the armature) at 30 amps when it was designed for 20 amps will more than double the power loss and so the temperature rise in the winding. (1.5 squared = 2.25).

On the other hand there is considerable thermal inertia in copper and battery charging after a start tapers off from the peak current rapidly so the time duration of that peak current for battery charging isn't long.

Another way to limit the current is through the resistancce of the wire betweeen the generator regulator and the battery. I have a run of 10 gauge on my JD 4020 with an alternator. Since the alternator is regulating the voltage at the alternator, the peak current even after a hard start is only 30 amps. If I had a fatter charging wire that peak current would be greater. But it charges the battery fast enough for me so I'll not change the wire. A 12 gauge charging wire 6' feet long would limit the peak current on your 20 amp generator to probably stay close to within its ratings. You might want that wire to have good high temperature insulation. My 10 gauge wire is rated to 250 degrees C. Its silicone insulated with a fiberglass braid. I don't worry about it being close to the engine hot parts like exhaust manifold. That's overkill, but I have a spool of it on hand.

But if you load that 20 amp generator to 30 amps with a lot of lights, its going to smoke. Brushes first, then commutator, then the armature windings.

Gerald J.

Replies:

• Re: 20 vs 30 amp voltage regulator John T 06:39:52 12/29/06 (1)
  • Re: 20 vs 30 amp voltage regulator Gerald J. 08:41:07 12/29/06 (0)

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