-=> Mike Ross said to Greg Mayman
 -=> about "VEHICLE LED'S" on 09-05-03  22:43.....

 MR> I measured 4.2milliHenry. It's not high at all.

If the cycle wheel has a circumpherence of about 7 ft, it will
turn about 3 times a second at 15 mph. Let's take someone's
stepup ratio of 35:1 for driving the dynamo. So the dynamo is
turning at about 100 times a second and generating an output at
100Hz.

4.2 mH will have an inductive reactance of 2.6 ohms at 100 Hz,
and if the lamp current is 400 mA it will drop 1.06 volts. This
is NOT insignificant for a 6 volt bulb.

 MR> That's true but if it is a load critical value (i.e. XL=XC=RL) then
 MR> there is no resonnant frequency and the effect of the capacitance is
 MR> spread out over a much broader frequency range.

Back to your books, laddie! It is resonant whenever XL=XC,
regardless of R.

 MR> The capacitor current will be at an angle leading the voltage while


What I was objecting to is your comment that the capacitor will
cause the current flow through the lamp to occur over a greater
part of the cycle of the output waveform. IT WILL NOT!!!!

 MR> There won't be many harmonics unless the pole steel behaves in a very
 MR> non-linear fashion and saturates.

Rubbish! Saturation is not needed.
 
Apart from hysteresis effects, the purity of the waveform
depends mainly on a sinusoidal buildup and collapse of the
magnetic flux in the pole pieces.

This buildup and collapse is NOT sinusoidal in most generators
unless they have been specifically designed for this, and is
especially non-linear in units that are designed for maximum
output at smallest size, and when purity of the waveform is
irrelevant.

Check it on your oscilloscope.

 MR> I've tested it on the circuit simulator and on the contrary the

 MR> The difference being that the circuit simulator didn't have the proper
 MR> generator model

In that case the results may not be anywhere near the truth.

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

... The real problem is not the overhead, it's the underfoot.
___ Blue Wave/386 v2.30

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