DC current flows better through wire with fine strands and gentle curves ?? - Page 1
Forum section: electronics / projects

author: calzap
author_rank: Frequent Contributor
timestamp: September 13, 2020, 09:02:53 pm
content: I was reading a pond management magazine, and there was a column giving pointers on solar power. Quote: “DC current flows better on higher strand count wire, thus saving resistance, which saves lost energy.” Huh? Maybe he just means it flows better through thicker wire.Quote: “DC current hates hard 90 degree turns. Imagine trying to navigate switchbacks on a mountain road with hard right and left turns instead of S-curves. Try to curve your wires to allow for better DC flow.” Don’t want the electrons to get motion sickness. Maybe he’s just trying to have folks observe minimum bending radius rules.Things can be dumbed down only so far without creating nonsense.Mike in California

author: magic
author_rank: Super Contributor
timestamp: September 13, 2020, 09:37:45 pm
content: Probably (mis)heard some rules and reinvented his own "common sense" justifications for themIt's not that hard to explain that cables have minimum bending radius or that thicker is better.

author: wizard69
author_rank: Super Contributor
timestamp: September 14, 2020, 03:21:18 am
content: I've seen a lot of nonsense published in the various solar power & homesteading magazines over the years. I use to pick up Home Power magazine every month and in the beginning it was pretty bad. Eventually they got better writers, not sure what happened to that magazine.Part of the problem is that some of these writers had an anti establishment mind set and couldn't bother to learn why some things are done the way they are. Others just seemed to have no technical education at all. This is one reason why I see high school physics as mandatory, far more useful to the general population than home economics. Probably should add in Algebra and trig.Quote from: calzap on September 13, 2020, 09:02:53 pm

author: Dave
author_rank: Super Contributor
timestamp: September 14, 2020, 11:46:47 am
content: Absolute nonsense. The only thing that matters for "better current flow" (minimal losses) at DC is the cross section of the wire. Higher strand count cables are more convenient for snaking around tight places, but that's about it. Same thing with the gentle curves, it only matters mechanically - sharp bends tend to result in broken strands and cracked insulation.Quote from: magic on September 13, 2020, 09:37:45 pmSounds about right.

author: NiHaoMike
author_rank: Super Contributor
timestamp: September 14, 2020, 12:34:34 pm
content: Most likely a complete misinterpretation of the skin effect, which only applies to AC and is generally only significant at high frequencies.

author: capt bullshot
author_rank: Super Contributor
timestamp: September 14, 2020, 01:16:56 pm
content: Quote from: calzap on September 13, 2020, 09:02:53 pmYes, of course. It's just the same when you operate a circuit upside down - all the electrons will fall out.

author: bsdphk
author_rank: Regular Contributor
timestamp: September 14, 2020, 01:52:05 pm
content: "DC current hates hard 90 degree turns"There actually is a kernel of truth in this, but in two very narrow and mostly historical contexts.The first is lightning arrestors. Lightning have slew-rates of kilovolt per nanosecond, and anything looking like inductance is in for a jolt of energy. (When ever you run an antenna cable into the house, tie a knot or make a few windings on the outside!) Therefore competently installed lightning arrestors always have gentle curves and 90° turns are strictly forbidden.The other case is in old telephone switch buildings where the DC power-bars carried enough current to interact with the earths magnetic field. That made subjected 90° corners to mechanical stress whenever the current changed dramatically (throwing switches, blowing fuses, shorts etc.)But yeah, probably not what they were referring to...

author: calzap
author_rank: Frequent Contributor
timestamp: September 14, 2020, 02:30:07 pm
content: Quote from: wizard69 on September 14, 2020, 03:21:18 amHome Power ceased publication at the end of 2018. However, they maintain a website (www.homepower.com), and PDFs of all back issues are available for free. Although some articles went off the rails a bit, it's still a valuable resource for those interested in generating their own power.Mike in California

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: September 14, 2020, 03:30:46 pm
content: Quote from: bsdphk on September 14, 2020, 01:52:05 pmBut that isn't actually DC though.

author: magic
author_rank: Super Contributor
timestamp: September 14, 2020, 04:49:36 pm
content: Quote from: capt bullshot on September 14, 2020, 01:16:56 pmNo joke, electrons actually have mass and therefore inertia, so imagine all those little balls slamming hard into a corner. At high enough current they will wear down the insulation in no time and start leaking by corona discharge.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: September 14, 2020, 06:22:51 pm
content: At corners the magnetic field has to be constricted on the inside of the bend, which should result in some apparent narrowing of the wire. Doubt if the originator of the comment has the physics to have generated this, or the math to calculate the magnitude of the effect, but there is a grain of truth to it.

author: Gyro
author_rank: Super Contributor
timestamp: September 14, 2020, 06:52:18 pm
content: The biggest reason for fine stranded wire and gentle curves is entirely practical. They are more tolerant of bending... and small bend radius can damage (and potentially split if exposed long term to UV) the insulation. Sensible and smooth bend radius is good wiring practice.