weird shaped torroidal magnetics? - Page 1
Forum section: electronics / projects

author: sarepairman2
author_rank: Frequent Contributor
timestamp: January 14, 2016, 06:01:04 am
content: So the typical torrid is the doughnut, E core, I core, r coreAre there oddball shapes made for weird purposes? with unsymmetrical geometries?i.e. donut with a taper on one side, asymmetrical figure 8 (like Klein bottle shape without the 4d)i know they have conical cores for wide band filtering.

author: sarepairman2
author_rank: Frequent Contributor
timestamp: January 16, 2016, 02:39:32 am
content: things go bump in the night

author: cdev
author_rank: Super Contributor
timestamp: January 16, 2016, 03:10:24 am
content: How about these?https://en.wikipedia.org/wiki/Minimal_surface

author: rdl
author_rank: Super Contributor
timestamp: January 16, 2016, 04:34:12 am
content: Check out some of the videos on youtube about the Wendelstein 7-X stellerator fusion device. Probably one of the most complex things I've ever seen. I think "weird shaped toroidal magnetics" describes it well.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 16, 2016, 04:15:15 pm
content: For transformers, nope. No point. Just pack as much flux into a simple-to-manufacture shape as possible, while leaving it easy to wind.You'll end up with a rounded rectangle cross section (better manufacturing -- ferrite powder is pressed into a cylindrical mold), with an inner (hole) diameter not quite half the outer diameter, and a height about half that again (give or take -- the height is adjustable in a cylindrical mold, another manufacturing advantage).So, that's basically what we have.For parts that do... interesting things, like nonlinear (saturating) cores, you can get some funky shapes, which are still topologically related, but aren't the smooth shapes we might think of:Sony used this sort of discrete resonant power supply in many products, especially high resolution Trinitron monitors. The core is pretty open, which allows for more winding space, a necessity due to the peculiar organization of the windings. Flux is a low priority on these, since the wire doesn't need to be large, and many turns can be wound to compensate for that.Ferrites that wind up in even more interesting applications, like particle accelerators, often have exaggerated aspect ratios, like thin discs, or a pot core with a very wide face. Typical purposes being beam sensors*, beam kickers, dynamic focusing, pulse generators (saturating shock lines, "magnetic compressors") and so on.*Bonus diversion:The kind of beam sensor I'm thinking of is pretty neat, because it's a current transformer, boiled down to its absolute physical purity.Particle accelerators (greater than fairly low energy levels) don't operate on continuous beams, but on 'bunches': wads of charge (of whatever charged particles are being zapped, usually electrons or protons). Which means, every time a bunch passes along the beam line (which is just a metal vacuum tube, usually kept quite cold to keep gas and contaminants down), it's a tiny burst of moving charge -- a current.All you need to do is wrap a current transformer around the beam path, and voila, you can detect the bunches! But you aren't going to do that with the kind of transformer that's got turns on it, not when the bunches are passing at relativistic speed -- you need to resolve sub-nanosecond current pulses here!What's done is, the beam line is cut open at some point. Effectively, the gap between the "particles are coming from here" pipe and the "they're going thataway" pipe experiences an induced voltage when a bunch passes the gap. The vacuum tube still needs to be sealed, you know, like a vacuum, so more metal is slapped on around the gap. But at a larger diameter, so as not to short out the pulse immediately. So the environment around the bunch goes like this: pipe, pipe, pipe; gap looking into bigger pipe; pipe, pipe, pipe...If a bunch of cables (usually coax, but any transmission line will do) are connected across that gap (you want them evenly distributed along the circumference of course), the voltage can be picked off. Indeed, it's necessary to do so, because the termination resistance of those cables prevents reflections (wouldn't want the bunches to generate interference with each other), and controls the amount of energy being drawn off at that point. Because necessarily, the bunches 'feel' the drag of a resistive sensor load; or by the same token, can be pushed along if correctly-timed pulses are driven into this same gap. Which is how all relativistic accelerators work, incidentally -- an RF power supply drives a chain of resonant cavities, the openings of which are presented to the beam, so that the beam absorbs energy (being pushed faster) exactly in step with the RF voltage peaks.Finally: ferrite doesn't necessarily have to come into any of this, but the size of that stepped-up-pipe-diameter should be kept to a minimum, to prevent reflections from its geometry. But that prevents much of a signal being produced, which is dumb. Solution: fill the larger pipe with ferrite, so the impedance is quite large even at fairly low frequencies (like, ~MHz instead of ~GHz). Indeed, the whole thing is a single turn current transformer, with a whole bunch of burden resistors in parallel (the transmission lines arranged around the periphery), instead of multiple turns and a single resistor.Tim

author: Assafl
author_rank: Frequent Contributor
timestamp: January 16, 2016, 07:01:13 pm
content: Sometimes shapes of toroids are to support different voltage gaps. Elongated for high voltage windings. Sometimes for supporting structure. Sometimes shaped for cooling (like pole pigs with oil cooling).Love the Wendelstein 7-X Stellerator reference.