Voltage regulators again

Hey Bus Driver - here's the deal: The two unit (two relay) voltage regulators are arranged so the "voltage regulator" relay also senses and limits output current. It does this with a low impedance (a few turns of heavy wire) coil wound outside the high impedance (many turns of fine wire) voltage sensing coil. The current coil is wired in series with the generator armature and sees all the generator output current. Now when output current exceeds the regulator, it pulls the regulator points open, dumping the field, thus reducing generator output voltage and hence current. In this photo of a 2 element regulator (from an SH), the regulator relay is the one closest to the camera. The current winding is the heavy copper coil wound outside the voltage sensing coil.

The two relay setup is a cheap, but imperfect solution. Adjusting the voltage setting affects the maximum current setting and vice-versa - ie. they are very difficult to adjust properly. Thus the more common 3 element regulators with separate relays for voltage, current and cutout control - while more costly, they do a more precise job of generator control.

Hope this makes senses! ...Bob M

Something else I've noticed: The generators provided with 2-element regulators are arranged with the 3rd brush set near the max current position, and the 3rd brush position is non-adjustable. At least that's how my SH an SM came from the factory. And that kinda supports my theory above. If anyone else knows different please advise!