Mag v4 Production complete

[02parkave 5,000+ posts]

Its funny how as soon as the T/S are posted no more arguing? I guess that was the point of it all then.

not really.. most of us are sitting in the corner laughing too hard

 

[Electrodynamic 10+ year member]

Kyle, the coil is 18.4mm long and the magnet is 85mm ID x 170mm OD x 20mm thick.

 

[newusername 10+ year member]

And I'm still not completely convinced that copper in the rebate is the best approach. This is one thing no one has ever answered for me: a rebate in the middle of the pole piece would make inductance slightly lower at rest than at any other position (since there is less steel in the core). The only exception to this would be on the outstroke when windings start to pass the top of the pole. Adding a shorting ring in the region where inductance is already lower seems like you are opening yourself up to greater inductance variation (increased harmonic and intermodulation distortion). I propose this only as a theory, and not data, but would love to see Le(x) that shows otherwise.

Time to revisit this.

When it comes to using shorting rings in a motor, the goal is generally to lower inductance and/or make the value of inductance vary less with position, Le(x), and vary less with current, Le(i). For what I explained already above, copper in the rebate isn't a great solution for Le(x). It isn't necessarily detrimental, but not perfect.

However, it does help greatly with Le(i) variation. First, let's look at the Le(i) data for a motor without copper in that rebate.

It is pretty obvious from that image that inductance is not constant with current (which is our goal). So how would we correct that? Well for starters, let's think about what the problem is: a variance with current. That means the problem occurs with current flowing through the coil. What region of the gap "sees" the coil the most? Easy answer: the center of the gap (since the coil rests there, all movement must start and return to this position at a rate equal to the frequency of the signal).

The real question here is one of what is called "eddy currents". In essence, eddy currents are what make inductance vary. A conductor moving through a magnetic field will cause a circulating flow of electrons, or a current, within the conductor. These circulating eddies of current create electromagnets with magnetic fields that opposes the change of the magnetic field, and essentially we are looking at inductance variation. Using copper in the motor helps short out these eddy currents, hence the term "shorting ring".

Back to Le(i): with more current through the conductor, we will experience increased eddy currents. Going back to the most common position of the coil (in the center of the gap), it is best to put copper in the place it is most effective. And since XBL^2 has that rebate, guess where eddy currents can short out to quite easily? Now, to make this effective over a wide range of current levels, you will need a fairly thick ring, but that is the beauty of the rebate: fitting a thick shorting ring in the rebate is extremely easy.

This is very intuitive: the place where the coil travels through the most, the place where varying current levels will most frequently be encountered, is also a good location for copper.

To wrap it up, here is an Le(i) plot for an XBL^2 driver with copper in the rebate:

 

[UndercoverPunk 5,000+ posts]

Solid post! When are you going into business? //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif//content.invisioncic.com/y282845/emoticons/tongue.gif.6130eb82179565f6db8d26d6001dcd24.gif

 

[UndercoverPunk 5,000+ posts]

avatar

I turned them off.

 

[Kyle_Keating 10+ year member]

Kyle, the coil is 18.4mm long and the magnet is 85mm ID x 170mm OD x 20mm thick.

thanks Nick!

When you are launching? I'm gonna pick up one or two.

 

[Hintzyboy 5,000+ posts]

thanks Nick!
When you are launching? I'm gonna pick up one or two.

Preorder starts Wednesday

 

[SocMunky 10+ year member]

Certainly a far cry from the old Mag. I have to wonder why it even retained the same name.

I think that perhaps this train of thought is why the t/s parameters were not released initially. Spec wise its not the same as the old mag, but I think he wants people to here it first before writing it off as being "not as good".

 

[bose301s 5,000+ posts]

Wow, I leave on vacation for a week and huge pissing match breaks out.

 

[James Bang 5,000+ posts]

Wow, I leave on vacation for a week and huge pissing match breaks out.

It was nice to not have your fanboy hearsay posts to read.

 

[Hintzyboy 5,000+ posts]

Is the pre-order any cheaper than if we wait to hear other reviews?

No, but they will sell out quick for the first couple runs I'm sure. If you're not in any hurry, then go ahead and wait

 

[ngsm13 5,000+ posts]

It was nice to not have your fanboy hearsay posts to read.

INdeed. Too bad he didn't die in a horrific motor vehicle accident.

nG

 

[bose301s 5,000+ posts]

Well, I finally caught up on this thread. As for the pissing match between Nick and Nick, neither of you are 100% correct in electromagnetics. Gaps in the motor will increase reluctance and will create extremely small field perturbations at the edges of the material, also called fringing. It will not cause this problem in the centers of the motor parts. Also, magnetic field lines do not flow randomly as claimed by Nick Morgan, they follow extremely predictable mathematical patterns which if your FEA software is up to snuff it will model perfectly. If stacked plates were so bad electrical transformers would not be made using sheet steel, especially when these transformers are in the vicinity of 95% efficient.

 

[UndercoverPunk 5,000+ posts]

No-one, wants your input.

 

[snoopdan 5,000+ posts]

No-one, wants your input.

lol.