alternating current

Discuss the technical details of an "open source" community-driven design of a polywell reactor.

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ohiovr
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alternating current

Post by ohiovr »

Could alternating current be developed in a collection grid by simply modulating the fuel ion injection rate?

Nik
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That's not AC...

Post by Nik »

That sounds suspiciously like un-smoothed DC...

IMHO, not a good idea unless you can run system reliably in pulsed mode at 50 (60) or eg 440 Hz to simplify switching.

( Don't some electric trains run on lower frequencies ??)

Hmm: But I must wonder if such un-smoothed DC *could* be used by 'skimming' the AC component for export and returning the DC to the mag-coils etc.

IMHO, it would need a non-standard design of transformer, possibly air-gapped / air-cored to tolerate the DC component.

Nearest equivalent I can remember is an obsolete but elegant motor control system that 'throttled' local transformer by running low-voltage DC through an auxiliary winding and partially saturating the core. Depending on format, it was known as 'magnetic amplifier' or 'saturable core transformer'. Google Images soon found examples.

Um, this is a distant cousin to CME / PowerGrid issues, where Aurora-induced DC ground currents bollix big voltage transformers.

D Tibbets
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Re: alternating current

Post by D Tibbets »

ohiovr wrote:Could alternating current be developed in a collection grid by simply modulating the fuel ion injection rate?
As Nik pointed out in the second post of this thread- pulsed direct current could pe produced, but not alternating current (+/-). Everything (almost everything?) electronic that runs from the current A/C grids would have to be junked.


Dan Tibbets
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dch24
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Post by dch24 »

It is surprising, but a large part of your existing household setup is fine on something like 110VDC. The wiring is fine. The fuses and breakers are fine.

Anything with a switching power supply is fine (computers, monitors, flat screen TVs, newer stereos and amps, printers, etc.). Even most new washers and dryers are fine.

Any AC heating element is probably fine, though a small number use a transformer and that design would break on DC. The doorbell 120V-to-24V transformer would need to be replaced with a (cheap) switching power supply.

AC motors once also worked on DC, though pretty much all AC motors now will not work on DC -- it's cheaper that way, unfortunately. With dual-mode (AC + DC) motors, fridges, power tools, fans, compressors (e.g. your forced-air heating and cooling), etc. would work fine.

There are things that really just work better on AC and are hard to replace with DC equivalents: flourescent "tube" lighting, microwave ovens, and UPS power supplies (but if you have DC mains you probably don't need what a UPS does -- a regular battery is a "DC UPS"). Oh yeah, and your Tesla Coil probably needs an AC supply or needs a redesign to use a solid-state primary.

D Tibbets
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Post by D Tibbets »

dch24 wrote:It is surprising, but a large part of your existing household setup is fine on something like 110VDC. The wiring is fine. The fuses and breakers are fine.

Anything with a switching power supply is fine (computers, monitors, flat screen TVs, newer stereos and amps, printers, etc.). Even most new washers and dryers are fine.

Any AC heating element is probably fine, though a small number use a transformer and that design would break on DC. The doorbell 120V-to-24V transformer would need to be replaced with a (cheap) switching power supply.

AC motors once also worked on DC, though pretty much all AC motors now will not work on DC -- it's cheaper that way, unfortunately. With dual-mode (AC + DC) motors, fridges, power tools, fans, compressors (e.g. your forced-air heating and cooling), etc. would work fine.

There are things that really just work better on AC and are hard to replace with DC equivalents: flourescent "tube" lighting, microwave ovens, and UPS power supplies (but if you have DC mains you probably don't need what a UPS does -- a regular battery is a "DC UPS"). Oh yeah, and your Tesla Coil probably needs an AC supply or needs a redesign to use a solid-state primary.
http://en.wikipedia.org/wiki/Switched-mode_power_supply
Looks like you are right. I was thinking that a step down transformer was the first step in the power supplies. At least most (all?) electronic switched supplies may not use this. So, OK, most of your modern electronics would work, and you could use an inverter for the rest. But what about fans (A/C motors as you mentioned) in your airconditioner, central heating, Power substation fans, fluorescent lights (at least the old veriaties), step up and step down transformers in power substations and pole pigs, old microwaves, electric trains and subways (?), etc. Alot of infastructure would need to be replaced.

Dan Tibbets
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ohiovr
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Post by ohiovr »

I don't think telling the world to go back to DC is going to work. AC has a multitude of advantages the first 2 that stand in my mind are:

1. Voltages and currents are easily stepped down and up
2. Very long transmission distances are allowed by high voltage AC

Number 2 could be accomplished with high voltage DC as well but what do you do with it once its at a house?

As I understand it, and as proposed, the output of the collection grid is dc. 12 volts DC isn't terribly difficult to convert to crude ac with a $50 inverter from walmart. But what do we deal with multi million volt DC, turning it into utility grade AC? Are there even semiconductors that could withstand a million volts with a few hundred amps? Is there a vacuum tube technology we could employ? Or would we have to resort to using superconducting motors turning generators?

I was just hoping for a cheaters way out by just modulating the fuel line. I thought it had a chance of working because the plasma is already so incredibly thin as it is.

dch24
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Post by dch24 »

ohiovr wrote:I don't think telling the world to go back to DC is going to work. AC has a multitude of advantages the first 2 that stand in my mind are:

1. Voltages and currents are easily stepped down and up
2. Very long transmission distances are allowed by high voltage AC

Number 2 could be accomplished with high voltage DC as well but what do you do with it once its at a house?

As I understand it, and as proposed, the output of the collection grid is dc. 12 volts DC isn't terribly difficult to convert to crude ac with a $50 inverter from walmart. But what do we deal with multi million volt DC, turning it into utility grade AC? Are there even semiconductors that could withstand a million volts with a few hundred amps? Is there a vacuum tube technology we could employ? Or would we have to resort to using superconducting motors turning generators?

I was just hoping for a cheaters way out by just modulating the fuel line. I thought it had a chance of working because the plasma is already so incredibly thin as it is.
I think pulsed mode and modulated operation are worth looking into.

But HVDC is not really a problem -- it has lots of existing uses in power transmission.

Short story: http://en.wikipedia.org/wiki/Electric_p ... ct_current

When HVDC is preferred to AC, and some history: http://en.wikipedia.org/wiki/High-volta ... ct_current

Wikipedia doesn't talk much about HVDC disadvantages, but engineering problems aside, switching from AC to DC usually reduces harm to the environment. The technology has come a long way, especially the newest valve designs. Some of it may even be useful in a polywell. Putting a polywell at some of the main HVDC installations in the US would benefit multiple power networks from a single source -- and the equipment to plug in a setup like that is already in place. :)

You hit the nail on the head talking about how to deliver power to homes... Even though the world disagrees on what voltage and frequency to use, AC power delivery makes a lot of sense for the "last mile" to each home. (And nobody would pay to replace all the installed equipment!) Delivering 150kV to a home is also not really an option, because it's so dangerous.

But there's a hidden gotcha in the engineering. Designing multi-point HVDC delivery is really, really sensitive to communication between delivery points (or multi-point generation for that matter). AC systems handle changing loads much better (because of how cheap it is to step the voltage up and down), but the "grid" is rapidly becoming linked enough that this wouldn't be a problem. Until something went wrong and took the communications out... Having a 100MW polywell that is sort of "locked in" to a single voltage setting might be the key to getting standardized HVDC generation and distribution, especially because when you need more power, you can "throw a switch" and get a relatively cheap 100MW anywhere you need it.
Last edited by dch24 on Thu May 14, 2009 5:14 pm, edited 1 time in total.

wfbrowniii
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AC or Not to AC

Post by wfbrowniii »

If a polywell reactor can be throttled from off to a maximum voltage in a sinusoidal fashion, then there are several ways to turn it in to bipolar AC without very much issue. I think the real issue is that the B-H reactor produces a higher DC voltage at full operating potential than anyone has yet dealt with. Something like 2 million volts. The highest DC line in operation is less than 500kV. [The so called megavolt bus down from Canada is actually one 500K line plus and one 500K line negative]
As they say, it's an engineering challenge, not a physics issue.... I hope. :) that's a lot of voltage to try and isolate.

Bill
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Morgan
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Post by Morgan »

Why can't we just use the DC current to drive an AC generator? Too lossy?

MSimon
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Post by MSimon »

AC motors once also worked on DC,
They are called universal motors. They had brushes.

The new trend in motor design is to use a switching supply to develop the (three phase) AC to run the motors.

Just think in about 100 years all the motors on the grid will effectively be AC/DC motors again. Especially as the price of power semiconductors drops further and the switching speeds increase with the advent of carbon nanotube transistors.

BTW the easiest way to get an AC component on top of the DC would be to modulate the grid voltage.

And think of it: A 100 MW self generating power amplifier for rock concerts. It might require two BFRs in a bridged configuration. In fact that might work for AC generation to the grid if the minimum output could be reduced by 1E3 or 1E4 below maximum output to minimize losses.

As an amplifier it would be fairly non-linear but that could be fixed with feedback or pre-distortion. A fast high sample rate FIR filter would probably do the trick.

Of course the 100 MW self generating power amplifier would probably need to be done at a fixed venue due to radiation shielding rqmts.

Don't stand too close to the speakers kids.
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MSimon
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Post by MSimon »

Number 2 could be accomplished with high voltage DC as well but what do you do with it once its at a house?
Normally there are inverter stations on the line to convert the HVDC to AC. In any case there is not going to be a 2 MVDC line to your house.

For now it looks like DC for long distance transmission and AC for City Loads.
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MSimon
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Post by MSimon »

Are there even semiconductors that could withstand a million volts with a few hundred amps?
Actually yes. There are now IGBTs that are rated 6.5 KV at a few hundred (I think maybe up to 2,000) amps. You put them in series. And the semiconductors would be avalanche rated so that small timing differences in turn on and turn off would not destroy the setup.

You can currently buy power supplies that use IGBTs to switch 100 KVDC. It is just a matter of extending that technology.

Of course you derate the transistors to about 1/2 the rated current and 2/3s the rated voltage.

Also note that the ratings of transistors is still going up. And before IGBTs became cost effective SCRs were used to do the switching. The circuits for that are more complicated but it was done where ever high power conversion was required. Say in HVDC to AC conversion stations at the end of a HVDC line.

The wiki is pretty good on this. Search around.
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MSimon
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Post by MSimon »

AC systems handle changing loads much better
This is true. But it is more due to transmission line effects. Which to some extent also operate with DC.

And yes - DC multi input/output lines would need to be co-ordinated.
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dch24
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Post by dch24 »

MSimon wrote:
dch24 wrote:AC systems handle changing loads much better
This is true. But it is more due to transmission line effects. Which to some extent also operate with DC.

And yes - DC multi input/output lines would need to be co-ordinated.
Yeah. Polywell (or IFR or anything nuclear) is good base load generation. In an ideal world where the power supply is practically all polywell, you benefit from being able to turn a polywell off with much less than 1 second notice. You might need to dump a few megawatts into heat and need some fancy setup to handle the switching but for now, HVDC isn't a problem...

kunkmiester
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Post by kunkmiester »

My dad mentioned this idea. You get pulsed DC out, which then just needs a transformer. Big challenge is controlling the field collapse on the down side of the DC pulse, which I'm sure people know how to do. A bigger challenge might be that you'd need to pulse the reactor at some arbitrary frequency, and you'd then have to change that down to 60 hz, and depending on how that works, it might not be worth it.
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