Siemens Dynamo

Reading the rating plate I see a problem or two. No rating is given for the field winding which normally be given on the plate thus making an external resistor selection difficult. The info given is that the Field is "COMP". which is unkown to me?

I assume your research confirmed that it is the field windings that come out to the terminal box? You may have to derive a suitable resistor by testing and measurement? Do you any test gear? Ohm meter, voltmeter etc But even if you were to work out what reheostat is required what can you actually get your hands on? Of course electronic would be easy.....

Does that then mean that it has two output windings and two field windings? I would have thought that the magnetic flux in the dynamo would be common to all windings despite two field windings, so maybe compound wound is something else.

The resistance will be the most important bit and Inductance unfortunately won't be much use as really is an inductive reactance varying with frequency. We can ignor that for now to simplify things.

I would in the first instance work out the resistance and voltage and size a resistor to that. Power disapation and resistance, and use a rheostat say 150% of that and see how it goes.

peter, i suspect you meant that the shunt winding is the higher resistance of the two. the series would carry the full current of the load and would be quite low resistance. the two windings' magnetic fields should be additive. sammm

unfortunately