Re: [TCML] PFC Question (again)

[David Dean <deano@xxxxxxxxxxxxxxxx>]

Hi

On Monday 26 May 2008 03:15:43 pm bartb wrote:
> Yes, in non-ballasted transformers like PIG's and PT's. For those that
> are already ballasted (NST's), it may not be max.
>
Well, maybe not if you are "charging an inductor", but I do not see how using 
more PFC capacitance than required to correct for the short circuit condition 
in a self-ballasting transformer could do any good when the perpose is to 
charge a capacitor. 

> >> Maybe label it "maximum" PFC value. And for self-ballasting transformers
> >> only. I do not know.
> >>    
>
> I'll probably get rid of it altogether.
>
> >> One thing though, I think where some folks might get in trouble, is when
> >> they want to design a Tesla coil around a transformer (PT or pig),  and
> >> they insert some number into the box called "rated mA". For example,
> >> lets take my 5kVA pig. If I use 5000/14400 or 347mA, it gives me 4997VA,
> >> 41499 Ohms, resonant cap 60nF, PFC 230uF, static LTR 95.9nF, and  SRSG
> >> LTR 166.7nF.
> >>
> >> If I use the actual measured short circuit current with the ballast
> >> (15/60 NST, dual primaries in series for 240V operation, both
> >> secondaries shorted) in place, of 85mA, it gives me 1224VA, 169412 Ohms,
> >> resonant cap 15.7nF, and PFC of 56uF. Also static LTR 23.5nF, and SRSG
> >> LTR 40.8nF.
> >>    
>
> Yes, but the program specifically says to insert the "rated" current.
> Not measured in a shorted or opened configuration. The outputs which
> follow are based on the rated data as set by the manufacturer.
>
Right. But you do not know what the "rated current" is. You only have kVA 
rating and percent impedance on the nameplate. And if you did have a current 
rating, it would be the maximum continuous current that could be drawn at a 
particular ambient temperature without overheating the transformer. A PT or 
pig is a constant Voltage device, as opposed to a constant current device 
like a NST. It is apples and oranges. KVA/V gives max continuous current if 
you are going to run for hours at a time, which is _NOT_  equivalent to the 
rated current of a NST. The short circuit current with the ballast in place 
is.
> >> Anyway, I think there may be more folks running resonant or LTR with
> >> their pigs or PTs than are aware. Just a guess.
> >>    
>
> I don't think so. Costs and energy across the gap are the reasons. I
> think most are STR. Some might try LTR, but were talking huge cap sizes
> and severe bang sizes across the gap. Highly unlikely and very expensive
> in both cap and gap costs.
>
I maintain my opinion.

later
deano



_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla