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[AMPS] 4-1000A Project

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Subject: [AMPS] 4-1000A Project
From: (Tom Rauch)
Date: Fri, 6 Apr 2001 11:21:38 -0400
> > The current circulating in a pi-net tank coil divides between
> > the load capacitor and the coax because they're effectively
> > in parallel.  
> That isn't correct. They are in series, but have different resistances
> loads across each one.

Woops, I should have been more clear. I was speaking of the 
capacitors at each end of the tank. The load capacitor is across 
the load resistance, so current in the capacitor is proportional to 
the voltage across the load and the reactance of the capacitor.  

The concept of being "in parallel" allowing summing of currents to 
obtain the current delived to that end of the tank or the circulating 
current is incorrect.   
> > between the output coax and the load capacitor.  At 1500W,
> > the coax will take 5.5A RMS and the load C will take the
> > same amount.  So, the circulating current will be about 11 Amps.

I re-did this for a circuit Q of 15 (input Q 14, output Q 1), and I get 

Load current 5.3 amps
Load capacitor current 5.3 amps
Inductor current 7.5 amps
Tuning cap current 7.5 amperes

The circulating current is not the sum of load and loading capacitor 



> That's close but not exactly true. Every component has a different
> current. Circulating current in the inductor is the highest at 6.6
> amperes.
> > As a rule of thumb for a Pi-net at HF, it looks like the
> > circulating current runs about twice the coax current.
> > Assuming you design for generally recommended Q's.
> > When designing for higher frequencies, Q's tend to run
> > much higher.
> That rule of thumb does not work.
> 73, Tom W8JI
> --
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73, Tom W8JI 

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