How does this configuration work for a step up transformer? - Page 1
Forum section: electronics / general

author: Beamin
author_rank: Super Contributor
timestamp: September 22, 2018, 07:39:30 am
content: He has the primary wrapped around the O shaped core with the secondary as that big black core that goes around the primary and the O core. Wouldn't he need the primary to also be in the same configuration as the secondary? Its like the secondary has two cores and is not symmetrical.In green I drew where the magnetic circuit "flux" is formed. I can see how this would work if the secondary was put on the other side but since its over the primary as well doesn't this make the coil of the primary act like another core the secondary's field has to interact with since the wires coming off form another loop/coil? Or is the primary invisible to the secondary because its not ferrous/iron?Does that large air gap in the secondary and the core effect things? Or does the fact that the coil goes through core all that matters? I'm trying to think in terms of a magnetic circuit where the core acts as the conductor.

author: Beamin
author_rank: Super Contributor
timestamp: September 22, 2018, 07:59:28 am
content: He also says that since its isolated you can get + or - 50 kv with respect to ground. How does this work? I thought at those high voltages the ground acts as - like how old telegraph lines worked where they just sent one + wire where the negative lead was just the ground in the receiving station.Where he says how you get -50kv:https://youtu.be/uCm1iPLVe8I?t=43m20s

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 22, 2018, 08:28:50 am
content: The magnetic circuit encloses turns from both the primary and secondary, thereby linking their fluxes.The remaining flux leakage is due to the space between primary and secondary. If close coupling is required, they need to be in the same position as much as possible. Apparently that's not required here, so it's fine.Tim

author: Brumby
author_rank: Unknown
timestamp: September 22, 2018, 09:20:02 am
content: Quote from: Beamin on September 22, 2018, 07:59:28 amThose old telegraph systems had the "negative" lead connected to the (literal) ground at BOTH the transmitting and receiving stations. The earth (dirt under your feet) was the second conductor is making a circuit. There was no magic voltage induced anywhere.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: September 22, 2018, 12:32:33 pm
content: They also send power that way.https://en.wikipedia.org/wiki/Single-wire_earth_return

author: Beamin
author_rank: Super Contributor
timestamp: September 22, 2018, 08:44:13 pm
content: Quote from: Brumby on September 22, 2018, 09:20:02 amI know they do that with ULF transmitters but they are putting Mw in and only going a hundred miles. Telegraph lines were longer then that much longer for some. They were also sending DC pulses and had to make it non hazardous to the humans and not radiate it all out the long lines.After reading that Wikipedia SWER is AC with the entire return path in the ground? The ground acts as a wire and some magic property of the ground like in RF systems?The earth ground system still mystifies me. Is it like a giant collection of electrons that you can dump positive current into/ take from to your positive, electron poor power source?Modern electrical grids don't rely on a path all the way back to the station or are there so many ground poles that each one acts like a short couple hundred foot long, wire segment? Lightning is electrons jumping from the cloud to the ground unless its a superbolt that's electrons jumping into the top of the cloud.

author: SeanB
author_rank: Super Contributor
timestamp: September 24, 2018, 01:20:18 pm
content: No, ULF is an antenna system, but because it is electrically very much shorter than a wavelength at the frequency in question, the impedance is very high, and the coupling efficiency is very low. You need MW of power put in to get a few dozen watts of radiated power, but that signal does cover the entire planet though, penetrating to a few kilometers down even in the ocean, enough to be detectable with a long wire and sensitive receiver.SWER is using the random conduction path in a mix of soil, ground water to provide a somewhat lossy conductor for electrical power transmission at high voltage. The voltage drop can be a few hundred volts at full load, but it is cheaper to make the connection and maintain it than to build a 2 wire high voltage line to make a metallic 2 wire circuit.Telegraph the same, cheaper to run one long cable to each side and have a ground return than to add the extra wire and insulators to provide the second.Earth ground is there to provide a common reference voltage, nothing special, just a defined point that will be roughly the same for all points nearby, and thus a common way for all voltage sources to be roughly the same potential difference from each other. Nothing special, it is a big connection that has some poorly defined resistance, somewhat variable reactance, has roughly the same potential in an area and is a convenient point to use.In power use it is there for safety, providing a way for there to be low voltage differences between the houses in an area, and to keep insulation from exceeding the rated voltages if the one line that is not referenced floats higher in voltage relative to ground for some reason. thus all power cables have some earth reference by some means, generally using a point on a transformer winding that is deemed to be the earth protective point.