[Amps] Choke-input with voltage doubler?

[John Popelish]

Larry Keith wrote:
> 
>>>
>>>My friend obtained a 1000-VCT brute of a
>>
>>transformer, weighs 25 lb. Old Chicago Transformer,
>>potted, looks mil-surplus. I assume it was made for
>>a choke-input filter. He wants to use the full
>>secondary with a full-wave voltage doubler. This
>>will be for a linear that will be used for
>>continuous-carrier DSB AM. Looks as though two
>>chokes would be required? Thanks.
>>
>>If you derate the transformer for output current,
>>the chokes are not 
>>necessary. 
> 
> So, I should de-rate by 10% or so?


Too many unknowns to say exactly what derating factor is required.
The goal is to keep the winding temperature in spec.

>> You can also lower the peak factor on the windings by 
>> adding a small inductance in series with the primary
>> to spread out the rectifier conduction time.
> 
> 
> Small as in the inductance of filament transformer in
> series with the primary?

Way too much.  Something more like a millihenry or so, like what is 
used in big speaker cross overs.  Unfortunately, those are not 
externally insulated to handle line voltage.  The choke has to handle 
the peak line current without saturating its core.  A drum core 
inductor could work:
http://www.jwmiller.com/pdf2/1140.pdf