quietguy wrote:
Just honing in on your post - you say the capacitor is open circuit - how did
you determine that? And how did you determine the diode is OK?

Just wondering whether you actually checked the capacitor with a proper
capacitor tester or just a multimeter?

And did you check the diode in both forward and reverse modes? ie with the
meter leads one way it should read almost a short circuit, and with the meter
leads reversed it should read almost infinity

David - who is very sus about the diode



CJT wrote:


James Sweet wrote:

I'm working on a generator for someone that recently just quit producing
electricity. On the label it touted the fact that it's a brushless
alternator; this is actually the first time I'd worked on one but I was
expecting much more inside it, certainly some sort of regulator module
but in fact it seems the only parts are a stator very much like that of
a large induction motor, a simple 2 pole armature with a diode mounted
to a heatsink, and a capacitor connected to two of the leads from the
stator. The capacitor is open circuit so that's an obvious problem,
diode checks out fine as do the windings so I'm assuming replacing the
cap will get it going.

What I'm curious though is how exactly does this thing work? The
armature has no connection at all to anything. I imagine it must receive
power through induction but how is the output regulated? Is there a
trick to manufacturing these? Given there's no brushes or slip rings I'd
have thought all alternators would be made this way unless there was a
disadvantage.

I don't understand why you think an alternator would need brushes or
slip rings. An alternator is an AC generator. The diode rectifies
its output (serving a function similar to what brushes would do in
a DC generator).

BTW, in some sense all good capacitors are "open circuits." However,
an ohm-meter should initially show a low "resistance" (until the
capacitor charges).




I checked the diode out of circuit with my Fluke multimeter's diode
function, so far it's never let me down, though the check does only pass
a few volts through it.

As I said in another post, the capacitor was thoroughly and properly
tested, trust me, it's open circuit. As far as I know, these oil filled
caps are internally fused so my guess is the plates shorted and blew the
fuse.