Mike,

On Tue, 4 Oct 2005 10:36:26 +0100, Michael Rigby-Jones wrote:

> Oddly enough I didn't receive my original question either

Nor did I.


> It was a bit of a long winded post on reflection so I'll shorten it:
> 
> Single phase alternator with no direct electrical connection to rotor.  Rotor has a coil, the ends of which 
are joined by a rectifier.  Stator has two coils, one for the output, one to provide field.  In this 
application (240v 50Hz 850W gas powered generator) the field was connected to the output coil via a simple 
current limiting capacitor.
> 
> It simply not a configuration I have seen before, and I was curious if it had a name.

I've certainly never seen or heard of it either - do you know how the coils are arranged (field on one side, 
output on the other, or interleaved, for example)?  How many poles are there?  I think the capacitor is 
probably for DC blocking rather than current limiting, or possibly give a bit of smoothing when the current / 
magnetic field reverses...

I wonder if the rectifier is to provide a sort of reverse-commutation, so you get something like a sine wave 
rather than half-wave rectified (I know this sounds counter-intuitive, but it's that sort of arrangement! :-)  
Was there some base excitation?  It must have either electrical feed or a permanent magnet somewhere, or it 
sould never get started.

I don't suppose you put a 'scope on the output?  I'd be fascinated to see if it manages a sine wave.

Cheers,


Howard Winter
St.Albans, England


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