Re:Even more diode stuff

Posted by alex on Sep. 14, 1998 at 22:04:19

In Reply to: Cutouts with Diodes - how is it done?
posted by Steve Mick on September 12, 1998 at 22:34:38

Hi guys,
I managed to get hold of a couple of spare generators and have rebuilt one to Henry's specs and put it back on my 1930 Tudor, The second is restored as a running spare and the third one I am in the midst of trying an experiment with.
I have mounted a large positive earth diode (300V, 40 A and 0.5 ohm forward resistance)in the back plate of the generator. The generator frame then becomes part of the diodes heat sink. I have insulated the earthed brush holder lifting it above earth in the same way the stock negative output brush terminal is and arranged the wiring so everything that used to go to earth via the generator frame (one brush and the end of the coil that went under the output terminal)now goes via the diode.Phewa bit of a mouthful.
Haven't had time to test it yet but it should work as a belt and braces setup as the original relay type cuttout will stay in place. I see what I have done electrically as exactly the same as putting a diode in series with the generator output terminal without the disadvantages of running a heat unsinked diode and having to worry about it floating near the armature.
The only negative (no pun intended) that I can see is that the diode body, about 3/4" diam. had to be placed close to what used to be the earthed brush. There is some restriction of the lower output current range because the adjustable brush travel limit is reduced by this amount.
I would be interested to hear any thoughts about the idea especially any negative aspects that I may have missed.
Regards to all who have seen the light and drive model As.
Alex