Guys, keep your pants on.

I have pm'ed Romero to ensure we will not be causing him any more grief.

Soon as I have a response, I'll let you know what I've found.



Penno

@nvisser
Thanks for the waveform images.
Can you tell us the magnet size and grade/strength you used to produce the waveforms?

Here's a rough drawing of how far the field extends.
Just used the NSNS with three magnet spacing.

Quote from: duff on June 24, 2011, 04:14:16 PM
@e2matrix,
Romero states the South pole is facing up...

However, the following is a little confusing.
It is from Romero's Forum

Hey Thanks for catching that and correcting it.  I'll try to fix my post.  I couldn't remember whether it was N or S up but did take a quick look at the PDF file and thought the red color in the diagram represented North.  50/50 chance and I got it wrong 

Quote from: wattsup on June 24, 2011, 04:55:37 PM
Very nice post but there is something definitely wrong there in frame #3.

In the first two you show only north passing or north and south passing, but regardless of what polarity and what distance between magnets, each magnet passage is producing a full sine wave with the TDC separating each one.

But in the third, the TDC is between each half cycle. That should not be possible regardless of how the magnets are set, close or far, each passage should be one full cycle with TDC in the center of the cycle. Unless what you are saying is that a cycle in fig 3 starts at positive or negative peak with the TDC between the peaks. That seems to be incorrect.

wattsup

Wattsup, that is good that you have the full sine wave for each magnet!
Its all to do with direction of motion, right?

However, #3 is correct. What happens is, with the correct magnet spacing the retreating north pole makes the same polarity peak as the incoming south pole... and they overlap!

When the magnets spacing is too far apart you get the "M" wave (with NSNS) but when 'just right' they overlap precisely, giving you the double height output peak!!!

Ron

Quote from: dutchy1966 on June 24, 2011, 01:14:40 PM
Mags,

This sounds very plausible to me. So in R_UK 's scopeshot i guess the approaching magnet first induces the negative spike, followed by the positive one (magnet is passed TDC). Is the flat bit in the trace nothing more than waiting for the next magnet to approach?

regards,

Dutchy

Yes.  The flat spot is when the rotor mag is not near the coil any more.   
As the mag approaches the coil, its field is attracted to the core. So any movement of the mag causes those field lines, attracted to the core in concentration, to cut the windings causing current in the whole winding, even though the field is only cutting one side of the coil. When the mag passes center, its field is still attracted to the core and now the field lines are cutting the windings on the others side of the coil. Same direction, same field crossing the windings, thus causing the currents to be induced in the opposite direction in the coil as a whole.

If you look at an alternator stator, the stator windings seem quite large, but the iron core is not very wide. So the armatures field is concentrated to that core and only cut the "part" of the windings that are "in" the core. The rest of the stator windings that are not in the core are just necessary to complete the windings circuit.

As the armature drags the field around, the field attracted to the stator core, the field enters the slit gaps on the inner side of the stator core and the field lines "cross" the windings creating current.

Our coils do the same but our gaps are wide and the core is small.

This is all very basic, yet some dont realize it.  ;]

Mags