[Amps] Rectifier diode strings

[Richard]

>Well, so far the only significant reason that has been offered, by Steve K, 
>is that for fast transients, the rectifier string "appears to be a string of 
>small capacitors." True enough, and indeed small they are. Down in the 10pf 
>range. 
>
True enough.

>Now. lets consider this in context. These rectifiers will typically appear 
>on 
>the secondary side of a large transformer that is not exactly a shining 
>example of high-frequency transformer design. Although I have never gone 
>looking for it, I would not expect to see much high frequency energy on the 
>secondary side. Especially peaks in the range of many kilovolts. 
>In order to get anywhere with this line of reasoning, we need to adopt a (or 
>some) generic models of transient pulses and look at the possible results. I 
>think it is futile, however, because of another practical factor. In a 
>typical full-wave rectifier, one leg of the rectifier is always in 
>conduction. This provides a path from the transformer, through the 
>conducting rectifier (very low R) through the filter caps (low Z for all 
except UHF 
>transients) and back to the transformer. Hence, any high-voltage transient 
>that would happen to make through to the secondary during the 'off' period 
>of  the other rectifier would likely be highly suppressed. I can't see how it 
>could ever even develop any kind of energy-bearing waveform across our 
>string of diodes/capacitors.
>
€  It can't, Eric.  Good logic, methinks.  However, with half-wave 
rectification, only the forward transient is stored in the filter 
capacitor, so shunt capacitors across the diode string is needed for 
reverse protection.   So how many turkeys use half-wave rectification for 
anode and/or screen supplies?  

>The basic technical issue at work here is still hanging wide open, and I 
>maintain my challenge to anyone to offer something we can chew on. That is, 
>how do you get all the rectifiers in the string into simultaneous 
>conduction? 

€  Use same-type diodes in series, and put  nothing  in parallel with 'em