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Re: Musein' and mathin'




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>Richard wrote:
>
>> All,
>> 
>> What follows is a long and perhaps for some, tedious diatribe, but is speaks
>> to many points which I and others have labored over on this list in the last
>> year or so.
>[snip]
>> Thus the peak current which we might expect in the tank is based on the peak
>> capacitor voltage and the surge impedance.  Such that... I peak =
21,000/50 or
>> 420 amps   From this we compute peak impulse power = 420 X 21000 = 8.82
>> megawatts!!!!!
>
>
>Shouldn't that be MVARs (Mega-Volt Amps Reactive), as the V and I aren't in
phase?
>The MVARs in the primary, of course, do not represent the real power in the
circuit.
>
>
>> Now do we really believe that we get this out the top of the coil?  Do we
>> really even believe we really get this in the tank circuit?  If we do we are
>> six times a fool.  Let's examine our wrong turns.  Was the math wrong.  Math
>> is never wrong!  Right?  If the math is correct and based on solid physics
>> and electrical concepts, where did we do wrong?
>> 
>> Answer.
>> 
>> It started at the wall plug and went down hill from there.  The biggest part
>> was the museins'- go back and count 'em.  It continues with the assumptions.
>> (count them too.)  and finally the math and its application is flawed.  Each
>> equation taken by itself is rock solid and in an isolated ideal circuit
>> (like in the stinkin' college lab) always solves out fine.  But all these
>> interact in a dynamic way that we did reckon or assume on.  Pspice and its
>> ilk can help here but then there are those nasty museins' and assumptions.
>> This is were pspice and such programs can die on their mathematical vine.
>
>
>It's true that even the best circuit simulator cannot make up for sloppy 
>circuit parameter modeling.  No argument there.
>
>
>> 
>> Richard Hull, TCBOR
>> 
>> I still sorta think 3 megawatts peak is close.
>
>
>That's about what PSPICE says my 20" (360kHZ) coil puts out, in VARs.
>Say, you're not one of those closet PSPICE users, are you?
>
>-GL
>
>Greg,

 You are right, of course, about the Mvar bit.

No I am not a closet Pspice type.   I have played with Pspice on a friends
CPU but found the endless input parameter requests and required assumptions
to produce same a bit ludicrous, and told my fellow engineers in the
department so.  A good old time engineer who has a "feel" for many aspects
of a situation might use Pspice to great advantage being a better guesser
and more creative human input engine than a lot of the younger wild eyed
chaps so taken with it.  By the opposite qwerk most grizzled engineers are a
bit anti-computer.  I think the combination might be the ultimate match made
in heaven.  When I use the CPU it is because it is just another tool.

Pspice, like anything else on the CPU, is not auto-erecting and talent is
still required to formulate a good model followed by the grueling input
machinations.


Richard Hull, TCBOR

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