A More Efficient Bridge Rectifier?

Good farm land doesn't care where it is. good farm land is where the soil is fertile whether it be the side of a mountain or the prairies in Saskatchewan.

Yes, that's a keeper. Many good points and ISTM an honest assessment of pros and cons.

Exactly. But it can be done gradually and "phased-in" as it were. It just needs to be formulated into a realistic proposal and then acted upon. There will be many engineering challenges, but that will be the "fun" part that also will inspire innovation and spur the economy, at least the personal economic welfare of electronic and electrical engineers.

Paul

Soil on the sides of mountains quickly ends up at the bottom of the hill. Very little of the good farm land of the world is at a steep angle.

g

Big transformers are also very efficient. Getting equal efficiency with something electronic is not very easy. The switcher still most likely has to have inductive elements so it takes some clever design to get there.

Can you say "Litz wire the size of may arm"

It may happen that industrial loads go DC first. There is more money per installed system to work with.

Most buildings use electronic ballasts in the lighting already. It would make sense to do the lighting load as its own system since they mostly already have there own wiring runs. The lighting load could have a DC-DC converter per run. Each would handle a few KW. They would be logically connected so that they start up in turn to reduce the rate that the current rises during turn on.

No big deal -- they already use aluminum strap for the 240V windings in pole pigs. The big hunk of ferrite would be smaller than the bigger hunk of iron, and volts/turn higher so copper losses can be lower for a given current density. The current ripple can be small because regulation on the input side is already fairly good, so you don't need much powdered iron to filter it, either. You can use big heavy metal boxes to seal in most of the EMI, and extra filtering (you *will* need more powdered iron for this part) to keep it off the wires.

Switching might be one of the bigger problems... switching HVDC is notoriously troublesome. Electronic switches just wouldn't be good enough for fault clearing and line switching. You still need mechanical beasties, and existing AC designs won't handle it (= still more infrastructure expense).

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

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I have to agree there would be massive objection at the suburban = residential=20 level. If you convert the pole rigs (or vault/pad transformers) too = massive=20 inductors to provide 120/240 60 Hz single phase you might get it to go.

Not only that those pole pigs have turns ratios of 10:1, 20:1 and even =

50:1,=20 i am not knowledgeable enough to evaluate the impact of that. Nor do i = know=20 much about how solid state systems are made for 12 kV and up.

Do they even? Seems to me there's kind of a hole in the middle... VFDs are easy enough to build (easy being a relative term) from watts up to ~1MW. I know they make SCRs rated for 2kV or so, and even more amps, so you can get a few solid megawatts from just a few of the things.

For HVDC, they make monster cascodes of them, able to switch ~1MV and some kA's with moderate efficiency (the voltage drop is large over an entire stack, so effiency tops out in the 90-95% range IIRC -- an awful lot of heat when you're switching gigawatts, but still not terrible overall).

I have no idea if anyone makes anything inbetween. Megawatt motors are often supplied by AC in the 10s of kV range, but I don't know if anyone makes a VFD-like supply using the same voltage internally (without passing it through a transformer to make ~1kV instead).

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

Going from a single semiconductor to two or more semiconductors in series seems to be a big threshold.

In EU and other countries using the IEC low voltage definition (< 1 kV AC, For HVDC, they make monster cascodes of them, able to switch ~1MV and some

There is no real demand.

Since big (1000+ MW) nuclear power station generators operate around

10 kV, I do not understand, why a

Right, it's easier to go with heavy ass conductors (~10kA) and medium voltages than to use transmission voltages (100-750kVAC) directly. And that's even just working with the electromechanical systems directly, no electronics at all.

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

Remember that peak voltage of an AC transmission line is 1.414 higher than the nominal RMS value. Normally this doesn't matter: you just space the conductors a little farther on the HV pylon---but when the cable needs to be buried or at the sea bed it needs to be much more expensive, so buried or undersea transmission lines almost always are DC.

A buried or undersea cable has a much higher phase-to-phase and phase-to-ground capacitance than an overhead line. These capacitances must be charged and discharged every half cycle, consuming a lot of reactive power and hence current. With a very long cable, all the current carrying capacity goes to this (dis)charging and no current can be delivered to the load.

In principle this could be compensated with a compensation station every few kilometers, but for reliability and serviceability, an undersea compensation station is not a good idea.

On a DC link, the cable capacitance is not an issue, it is charged once when the power is applied and finally discharged into the load, when the source is disconnected perhaps within a few months.