Re: Parallel and Series LCR Circuit Qs

[ghub005-at-xtra.co.nz (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

On 21 Aug 2000, at 18:36, Tesla list wrote:

> Original poster: "Malcolm Watts" <M.J.Watts-at-massey.ac.nz> 
>
 
<snip>

> > Richard
> > 
> > Surely a source impedance of zero ohms means that your power 
> > source also has a zero output voltage? (Ohm's law)
> > 
> > For maximum power transfer you will need to make the TC's output
> > impedance equal to the complex conjugate of the spark impedance i.e.
> > match the resistive componets and reverse the reactive component.
> > This will give you a theoretical maximum efficiency of 50% (as at
> > least half of the power will always dissipated in the source
> > impedance).
> > 
> > Of course, the spark impedance probably isn't linear - so all this
> > may be moot. I would recommend that you just aim for the ballpark
> > and concentrate on reducing losses in the SG and primary etc etc.
> 
> Technically a voltage source has an internal impedance of zero 
> ohms. By definition this means it can deliver any amount of 
> current asked of it with no voltage drop at its terminals. A 
> large lead-acid battery comes close to this definition as does 
> a power station.
> 
> Regards,
> Malcolm
> <snip>

Fair enough

I almost always instinctively think of a power source as being an 
ideal current source in parallel with an internal impedance (the 
Norton equivalent?). With that model, a zero-impedance intuitively 
results in a zero-output voltage.

Of course, the model clearly makes no physical sense if the output 
impedance is zero (because of the infinite loop current etc). As you 
suggest, the Thevenin equivalent gives a much more useful (and 
realistic) result. 

Isn't it funny how unconscious assumptions can undermine the 
process of interpretation! 

Best regards,

Gavin