Re: voltage drop of a old silenium rectifier

John Popelish wrote: 
tucker@xxxxxxxxxxx wrote:

 I want to build a hi current 12v supply, I know where i can buy a
6-12v 100amp battery
charger cheap. This charger had silenium (dont know the proper
spelling) rectifiers.  Im
thinking the transformer must be alot higher voltage than a similar one
in a modern charger
using silicon diodes. If i know the drop than i can figure the
transformers output voltage.
 So does anyone know the voltage drop of these old rectifiers?


The normal drop (at rated current) of selenium rectifiers is about 2 volts per plate.

After Bill posted .9 volts, I began to doubt my memory and looked it up in a reference (Reference Data for Radio Engineers, 5th Addition).

A typical rating is 27 volts reverse per cell, 600 mA to 1950 mA per square inch (that 100 amp supply must have a lot of square inches of selenium) and with a capacitive or battery load, 1.6 volts drop at rated average current. However, they have an essentially resistive aspect from about .5 times rated current to 2.5 times rated current. That is, the forward drop climbs linearly from about 1 volt at .4 times rated current to 3 volts at 2.5 times rated current.
.

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