[AMPS] Bridge vs. Doubler

[Rich Measures]

>Rich wrote:
>
>"because a doubler is full-wave -- i.e., current flows on both half 
>cycles.  The trouble with half-wave is that DC flows in the transformer's 
>secondary winding."
>
>I'm afraid that I can't agree, but maybe we're arguing semantics.
>
€  Your e-mailer application is not doing attribution marks correctly, 
Dave. 

>Assuming the typical doubler schematic, on the positive half cycle one
>rectifier charges the "top" capacitor.  On the negative half cycle, the
>other rectifier charges the "bottom" capacitor.  So, each capacitor gets
>charged half of the time.  Maybe this is full wave, but its not full wave
>like a bridge where the entire capacitor bank gets charged on both 
>positive and negative half cycles.
>
>I still maintain that a doubler is simply two "stacked" half wave
>rectifiers, and that the regulation will always be inferior to a full
>wave bridge, assuming equal total C and reasonably equal transformer
>design and sizing.

€  Not a sound bet.  
>
>Rich, what I don't understand is:
>
>1) What do you mean by "half wave rectifiers have DC in the winding"

€  with a DC ampmeter in series with the winding and one sees a DC 
current.  Transformer are not at all happy with DC flowing in a winding.  

>and why does the doubler not have this condition?
>
€  with a DC ampmeter in series with the transformer winding of a FWD 
supply, one sees zero DC current.  

>2) Why does the FWB need "four times the wire in the secondary?  

€  It does not.  The length of the wire is double.  

>I would understand two times...
>
€  Compared with a FWD winding, the FWB winding requires twice the number 
of turns -- i.e., the wire is twice as long.  In order to accomodate 
twice as many turns in the transformer, the wire diameter must be 
smaller.  However, accomodating twice as many turns means that more 
layers of wire must be insulated from each other with additional layers 
of paper.  To compensate for more paper, the diameter of the wire must be 
made even smaller.  The bottom-line is that there are relatively more 
than four times as much R in a winding designed for FWB service.  .  .  
Yea, verily, Mo' copper is mo' betta than mo' paper.    

-  cheers, Dave


Rich...

R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures  


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