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Forum Index : Electronics : Calculate how many conductors can fit through a hole
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Haxby Guru  Joined: 07/07/2008 Location: AustraliaPosts: 423 |
Was there an online calculator somewhere that shows how many conductors can fit through a hole? I want 70 conductors through a 54mm diameter hole and need to know how thin they should be... |
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phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 2135 |
With a rough back-of-the-envelope calculation I get a touch over 5mm OD for the wires. |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
The magic answer is..... Seventy 5.6mm wires fit through a 54mm hole. https://www.engineeringtoolbox.com/smaller-circles-in-larger-circle-d_1849.html Edited 2021-06-30 13:27 by Warpspeed Cheers, Tony. |
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| Haxby Guru Joined: 07/07/2008 Location: AustraliaPosts: 423 |
Thanks guys. |
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| bob.steel Senior Member  Joined: 27/02/2020 Location: AustraliaPosts: 188 |
Course if the hole stretches ,well! |
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| Godoh Guru Joined: 26/09/2020 Location: AustraliaPosts: 458 |
Hi Haxby, it may seem counter intuitive but as a former electric motor rewinder., I would often try a few different guages of wire, in a motor if the slots looked full on the winding I was going to replace. Often I would find that instead of a large number of small wires in parallel, that a smaller number of larger wires would actually leave more room in the slot and make the wind easier. What happens is that as you put the windings into the slot they don't stay neat and parallel, it is difficult to keep them all straight so they bunch up. In a transformer winding by hand, such as a torroid, it may not happen as much if you are very careful. It will depend on whether you have a bit of scrap cable of the size you want to use to test it out. I used to cut enough short bits of magnet wire and put them in the slot just to test it out. It was amazing how many times a tight winding became easy by changing the guages. The way to get the calculations right is to work out the cross sectional area of the wires in parallel and find other combinations of conductors that add up the same. Pete |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
I can see that laying a winding carefully into a rectangular slot with relatively tight U turns between slots might be rather a challenge to get the conductors laying flat in neat layers without tending to pile up around the sharp corners. And thicker wire should I would think be easier to deal with, especially if it happens to be a convenient size with relation to slot dimensions. As soon as you start getting crossovers around the corners you are getting into deeper and deeper trouble. Toroids are rather different in that its much easier to lay the conductors parallel right where they pass through the hole. Heaps of room between turns going around the outer circumference as it all spreads out. Some things will be obvious to the old toroid winding veterans, but the novice may not have thought of. The fine wire with the highest turns always goes on first. It could be either the primary or the secondary, but always the higher voltage winding goes on first. The reason being the smaller wire produces a much smoother winding. Very heavy gauge wire will produce a lumpy winding, which on the outer final layer does not matter. Much more difficult to wind fine wire over a very lumpy previous layer. The other fascinating thing about toroids is how many turns will fit onto each layer. If you start with one single central wire, six more wires will cluster very neatly around that, a perfect fit. I think everyone knows that. What may be a surprise is the next layer will fit exactly six more wires than the layer underneath. And the next layer again six more wires than the layer underneath that. So centre wire = 1 wire. First layer 1+6 wires = 7 wires total Second layer 1+6+6 = 13 wires total Third layer 1+6+6+6 = 19 wires total and on and on it goes forever. But the really interesting thing for us, is it works the other way too. When winding a hypothetical toroid, (without any insulation between layers) theoretically, if you find after measuring your hole, and from the wire diameter, lets say 280 turns will just fit around the inner circumference in the first layer. You can assume that the next layer to go in will be six turns less or 274 turns. Third layer again six turns less 268 turns and so on. Actually its never quite that good, extra insulation and small gaps between the wires reduce what will fit, but its a pretty good initial guide to estimating what might be possible when trying to figure out if a design is even possible. So if 280 turns will fit on the very first layer, in a perfect world, on the sixth layer 36 less turns (244) might fit. It won't in practice. But if you only need say 235 turns per layer it might be a pretty safe bet that six layers of 235 turns should fit onto that core. Edited 2021-07-09 10:29 by Warpspeed Cheers, Tony. |
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| phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 2135 |
Unwound a piece of heavy power cable. The rule of 6 more per layer works but not quite in the way shown. First layer 1+6 wires = 7 wires total Second layer 1+6+(6+6) = 19 wires total Third layer 1+6+(6+6)+(6+6+6) = 37 wires total |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Yes you are quite right Phil. The important thing to remember is that each successive layer is 6 more. Cheers, Tony. |
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