-=> Mike Ross said to Greg Mayman
 -=> about "VEHICLE LED'S" on 09-08-03  23:43.....

 MR> You are using the "inductive reactance" of 2.6 ohms as if it was a
 MR> real resistance but it isn't. You have to find the impedance to get the
 MR> real voltage across the lamp. Let's assume in this case the lamp
 MR> presents a constant 12 ohm load, then Z=12.28 ohms. The voltage across
 MR> the lamp will be I * RL = (6/Z) * 12 = 5.86 V and totally not like 6V -
 MR> 1.06V! 

Mea culpa.
 
 MR> That's true but if it is a load critical value (i.e. XL=XC=RL) then
 MR> there is no resonant frequency and the effect of the capacitance is
.....^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

 MR> Of course, it is resonant any time XL=XC,

So don't say "there is no resonant frequency." Let's try to avoid
such sloppy terminology.

   but I assumed you understood
 MR> that maximum power will be transferred from the generator to the load
 MR> when XL=XC=RL.

I understand nothing of the kind!

The maximum power is transferred when the effective OUTPUT
RESISTANCE of the generator is equal to the resistance of the
load. The effective output resistance of a resonant generator
usually is NOT equal to Xc or Xl.
 
 GM> What I was objecting to is your comment that the capacitor will
 GM> cause the current flow through the lamp to occur over a greater
 GM> part of the cycle of the output waveform. IT WILL NOT!!!!

 MR> Why not? In the above circuit simulator example we can see how a

Forget your simulator, and go back to basic theory.

1. If the waveshape of the current is sinusoidal without the
capacitor, it will still be sinusoidal after the capacitor is
added. The current will NOT flow through the lamp for a greater
part of the cycle.

2. The only way you can make the current effectively flow for a
greater part of the cycle is to change the waveshape towards a
square wave, which implies a greater amplitude of harmonics.
Adding the shunt capacitor will have the reverse effect.

 MR> specific critical value of capacitance becomes useful in pulling up
 MR> the output voltage across a broad frequency range rather than simply at
 MR> a single resonant frequency.

That is a lot different from saying that "the capacitor can
supply current to the lamp when the dynamo output goes through
zero and hence the current will flow for a greater part of the
output cycle."

 MR> Okay, I will try to find a longggggg extension cord... 

What do you need a long extension cord for? In this case, the
reults you get with the bicycle on a stand in your workshop or
garage are going to be the same as the ones you get on the road.

After all, we don't need to figure in windage or road surfaces to
find what the dynamo is going to do at different speeds as
regards brightness of the lamp and drag on the wheel.
 
 MR> That's a possibility but however improbable what remains is the truth.

"When you have eliminated the impossible, whatever remains,
however imprable, must be the truth."
                A. Conan-Doyle, "The Sign Of Four".

If you must use quotations, you could at least get them right,
AND pick those that are appropriate.

In this case, since you admit that your simulator model of the
dynamo may not be accurate, a more appropriate quote would be
"GIGO - garbage in, garbage out." (origin unknown).

From Greg Mayman, in beautiful Adelaide, South Australia
   "Queen City of The South"    34:55 S  138:36 E

... Runtime Error 6D at 417A:32CF: Incompetent User.
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