PLUR 2 Evolution

[Borat]

hello it's me again - George Chkhartishvili

that's right boys and girls. i took the most linear ( and dare i say, elegant ? ) ribbon motor design ( my own, if you recall ) :

Plur

and made it MORE LINEAR

behold ! PLUR 2 Evolution



if you refer to the original you will see that the difference is the addition of end caps. these are regular magnetic steel used to build speaker motors.

the result is a DRAMATIC improvement in symmetry resulting in dramatically improved field uniformity.

in fact PLUR 2 Evolution can be optimized for ABSOLUTELY uniform field.

the reason you can see a bit of "noise" in the flux lines on that graph is constructed the outline of the neodymium out of just 3 arcs wit the dimensions optimized by eyeballing the result. i spent about 10 minutes optimizing the shape. the shape can easily be, as i said, easily optimized for ABSOLUTE field uniformity.

once again i encourage those of you who like to build your own ribbons to build a prototype of this, as i don't really have time/money/energy to build one myself at the moment.

ps: this particular simulation is for a motor that will accomodate a 4" wide ribbon for an XMAX of about 10mm. the basic dimensions haven't changed but thanks to greater uniformity now the ribbon can take advantage of the entire width of the neodymium.

thanks for stopping by.

George Chkhartishvili.

[Borat]

think of an underhung woofer. the reason they are so linear is because the field is controlled on all sides of the voice coil by the gap.

in a regular woofer the parts of the voice coil outside of the gap are hanging in an uncontrolled field which is wildly nonlinear.

similarly in a regular ribbon motor the field is just hanging out there. it couldn't possibly be uniform because it is only being controlled from one side.

here in PLUR 2 Evolution the field is contained on all 4 sides. this is what ulimately enables the uniformity. and this makes it similar to an underhung woofer motor in some philosophical sense. although an underhung woofer doesn't control it on all 4 sides so actually there is no analogue to this design at all.

[Borat]

Some labels from FEMM in case it's not clear what's going on.

[thadman]

Very interesting

Aside from the uniform field, wouldn't the steel increase the inductance of such a system, resulting in a smearing of transients and temperature dependent field?

Recall the behavior of the core material in transformers. I believe you will observe air-core transformers to have significantly lower inductance compared to a transformer with a steel core.

[thadman]

Have you thought of replacing the steel caps with neodymium caps?

I don't think you'd observe the increase in inductance