Author Topic: Caps (Read 1935 times)

GreenTeam · « **on:** July 15, 2020, 09:27:46 AM »

In designing or assembling a little turbine ,is it advantageous to add capacitors to the output lines? To increase the power it creates or stabilizes it? Could one even add diodes or Voltage regulators?

dnix71 · « **Reply #1 on:** July 16, 2020, 02:36:46 PM »

For a given wire size, alternating current is transmitted more efficiently than direct current. As long as the voltage can be safely transmitted close to the point of use, you should do your rectifying there. Your power conversion board is determined by what's coming in, versus what you need out.

SparWeb · « **Reply #2 on:** July 16, 2020, 03:29:47 PM »

If you're looking to get DC out of a 3-phase alternator (of any size) then rectifiers are the way to go.
Capacitors are a minor modification that you can try later - if you need the extra 10% that you may or may not get. How much you get depends on the alternator design.

GreenTeam · « **Reply #3 on:** July 17, 2020, 01:23:34 AM »

The extra ten percent may or is required. Or at least power stability. I understand that capicitors somehow take care of something called "ripple"? Is ripple bad for charging a battery bank? Or would it be nullified by a inverter?

ruddycrazy · « **Reply #4 on:** July 17, 2020, 05:14:34 AM »

My first wind genny was a F&P washing machine motor and rather do a rewind like everyone else was doing I just used a 100 series (1mm wire) wired in Delta unmodified Then using 400 volt 470uf caps back to back and in series with the AC output.

Without the caps the average current was 6-7 amps @ 24 volt, now by putting the caps in the current jumped to 11-13 amps. Well the rest is history and I went on to make a motor conversion.

To cut it short the wind genny I have up now is the same F&P and it's doing a fine job of charging the forklift battery in my shed.

Cheers Bryan

dnix71 · « **Reply #5 on:** July 17, 2020, 03:18:32 PM »

GreenTeam Capacitors smooth the ripple. But you haven't said what you intend to use the power for. You also haven't said how many phases/poles there are coming out in your genny and how close the genny is to the point of use for the power it makes. If you want to keep it simple and not spend lots of money unnecessarily, we need lots more details.

Making the most of your power means impedance matching from end to end, but sometimes that isn't practical.

GreenTeam · « **Reply #6 on:** July 18, 2020, 03:34:59 PM »

Quote from: dnix71 on July 17, 2020, 03:18:32 PM

GreenTeam Capacitors smooth the ripple. But you haven't said what you intend to use the power for. You also haven't said how many phases/poles there are coming out in your genny and how close the genny is to the point of use for the power it makes. If you want to keep it simple and not spend lots of money unnecessarily, we need lots more details.

Making the most of your power means impedance matching from end to end, but sometimes that isn't practical.

Right! sorry, my bad. Right now, I a,m doing a proof of concept because I said ahead of time that I can beat the infinity air:P Hands down lol. So, the infinity air is a little teensy wind turbine that is used to power up a smart phone. It producers 10 watts at a freakin 40 K/h wind lol. So, I am dismantling a 4.5 inch hove rbpard motor, which has 18 coils made from 0.5mm wire x2 and 3 phase. It also has20 magnets per stator. So, I am using the three phases rewound into 6 coils axial flux with 8 magnet poles. All together I have 40 magnets from 2 wheels. So, I may use both stators and do a double stator build woth 3 magnet rotors. Basically, I geuss 5v and 10 watts is my bottom I want to produce. So far, I am cutting my mold now, and its 4 inches diameter.

dnix71 · « **Reply #7 on:** July 19, 2020, 10:15:17 AM »

Okay. You want to power a cell phone. You will definitely need NO ripple. You need a voltage regulator and small battery on the output side and caps behind that. I have an Engel fridge and they have a bold warning printed on the fridge not to use a battery charger in place of a battery because the ripple could damage the circuit/compressor. A cell phone is also delicate.

The hand-held wind up usb chargers are designed like you want. The hand cranking produces nasty wild a/c, which is smoothed by caps to charge an internal battery. The output is clamped by a voltage regulator to usb standards.

https://www.amazon.com/American-crank-powered-flashlight-smartphone-ARCCR100R-SNG/dp/B003BYROUQ

WindyOne · « **Reply #8 on:** November 24, 2020, 10:12:28 AM »

Quote from: dnix71 on July 16, 2020, 02:36:46 PM

For a given wire size, alternating current is transmitted more efficiently than direct current. As long as the voltage can be safely transmitted close to the point of use, you should do your rectifying there. Your power conversion board is determined by what's coming in, versus what you need out.

For a given size wire, equivalent Volts and Amps ... DC is more efficient than AC.
Per Sandia National Labs ...
Utility Companies have already installed DC Transmission Lines that are more efficient than AC Transmission Lines
Equivalent DC Power reduces transmission line losses by 30% to 40% vs AC Power

What is the "source" for your statement?

Adriaan Kragten · « **Reply #9 on:** November 24, 2020, 12:15:19 PM »

Quote from: dnix71 on July 16, 2020, 02:36:46 PM

For a given wire size, alternating current is transmitted more efficiently than direct current. As long as the voltage can be safely transmitted close to the point of use, you should do your rectifying there. Your power conversion board is determined by what's coming in, versus what you need out.

I don't agree with this statement. It is just the opposite if you talk about a 3-phase current which is rectified. The rectifier should be placed as close as possible to the generator. It is easy to prove that you have the same copper losses for a DC-current flowing in two wires of a certain cross sectional area as for an AC-current flowing in three wires of the same cross sectional area. So for the same losses, you need 50 % more copper if the wires are guiding an AC-current. This is because the AC-current is flowing only during 2/3 of the time in each wire if the winding is rectified in star. Rectification of a 3-phase current is explained in my public report KD 340.

Bruce S · « **Reply #10 on:** November 24, 2020, 02:42:30 PM »

Quote from: WindyOne on November 24, 2020, 10:12:28 AM

Quote from: dnix71 on July 16, 2020, 02:36:46 PM
For a given wire size, alternating current is transmitted more efficiently than direct current. As long as the voltage can be safely transmitted close to the point of use, you should do your rectifying there. Your power conversion board is determined by what's coming in, versus what you need out.

For a given size wire, equivalent Volts and Amps ... DC is more efficient than AC.
Per Sandia National Labs ...
Utility Companies have already installed DC Transmission Lines that are more efficient than AC Transmission Lines
Equivalent DC Power reduces transmission line losses by 30% to 40% vs AC Power

What is the "source" for your statement?

We're going to need your "source" for these statements. Including the math would be nice too.

If the last statement were even close to being true , , , why then are all the high-power lines AC?

Bruce S

richhagen · « **Reply #11 on:** November 24, 2020, 05:10:07 PM »

If you take an incremental slice of time and look at the V=IR and P=IV of the system, they would be equivalent. I would think that inductance and capacitance of the system would give DC a slight edge intuitively as such properties would resist changes in voltage and current. Impedance = resistance plus reactance for example. Additionally, if I put a coil of wire near a high current AC line, I can pick up power from the changing magnetic field, which would show up as a loss in the transmission of power. This would not be the case for DC as the magnetic field would not change so much and it is a changing magnetic field that would be inducing such losses.

The actual reason that AC won out in transmission over DC back in the day was that transformers could be used to convert the voltage from high voltage for lower losses in transmission to lower voltages, suitable for use in motors and lighting and other industrial and household uses. At the time, there was no easy way to convert from high to low DC voltage, and even currently it is harder than converting AC. Edison advocated for DC generation and transmission, but without being able to take advantage of high voltage transmission, there was not enough copper in the world to electrify the U.S. He was limited to having a system with large numbers of small generating stations and huge costly cables. AC won out because it was better in that regard since you could use transformers to convert the voltage to high voltage and large central power stations to send electricity over long distances as a result.

Now that the ability to use and convert high voltage direct current, there has been research into creating a high voltage DC backbone to connect grids and send power across the country in voltages in excess of a million volts DC in order to further stabilize our grids and reduce losses and costs of transmission. So far as I am aware, no such system has yet been implemented. Just my thoughts on it, Rich

mab · « **Reply #12 on:** November 24, 2020, 08:40:33 PM »

I think there's a bit of confusion about context here:- there's a big difference between transmission from a private windmill to your house and utility scale long-range transmission.

basically, if you want to run electricity over a distance then higher voltage is more efficient.

As Richhagen just said, AC became dominant for utility scale transmission lines due to the ability to transformer the voltage UP for transmission and DOWN for use as required. The problem with AC at high voltage is capacitance of the lines(ironically coming back to the original subject of this thread); this causes the powerfactor to change over the distance and requiring the utility to install powerfactor correction stations which are expensive and waste energy. IIRC 1000km is the rule-of-thumb practical distance limit to HVAC overhead power transmission - you can run longer distance but the PF correction stations and line losses make it expensive - and nowadays it's cheaper to install HVDC. If you're dealing with underground/underwater transmission then the practical limit for AC is ~60km IIRC.

Richhagen - I'm not sure i haven't misunderstood your meaning but HVDC has been around for a while - albeit at <1,000,000V

the following wiki page describes the 1st UK/France HVDC as being commissioned in 1961 (now decommissioned) and the 2Gw ±270Kv bipole replacement was commissioned in 1986 and still in use, along with several others to europe & ireland:

https://en.wikipedia.org/wiki/HVDC_Cross-Channel

There's a link on that page to a whole list of ac and dc transmission lines: I did see the uk western link (built to bring wind power from Scotland to England)is 600kv 2.2Gw and there are some active ±320 Kv in europe, and one planned in Italy for ±500Kv

mab · « **Reply #13 on:** November 24, 2020, 08:53:47 PM »

Quote from: mab on November 24, 2020, 08:40:33 PM

I think there's a bit of confusion about context here:- there's a big difference between transmission from a private windmill to your house and utility scale long-range transmission.

basically, if you want to run electricity over a distance then higher voltage is more efficient.

As Richhagen just said, AC became dominant for utility scale transmission lines due to the ability to transformer the voltage UP for transmission and DOWN for use as required. The problem with AC at high voltage is capacitance of the lines(ironically coming back to the original subject of this thread); this causes the powerfactor to change over the distance and requiring the utility to install powerfactor correction stations which are expensive and waste energy. IIRC 1000km is the rule-of-thumb practical distance limit to HVAC overhead power transmission - you can run longer distance but the PF correction stations and line losses make it expensive - and nowadays it's cheaper to install HVDC. If you're dealing with underground/underwater transmission then the practical limit for AC is ~60km IIRC.

Richhagen - I'm not sure i haven't misunderstood your meaning but HVDC has been around for a while - albeit at <1,000,000V

the following wiki page describes the 1st UK/France HVDC as being commissioned in 1961 (now decommissioned) and the 2Gw ±270Kv bipole replacement was commissioned in 1986 and still in use, along with several others to europe & ireland:

https://en.wikipedia.org/wiki/HVDC_Cross-Channel

There's a link on that page to a whole list of ac and dc transmission lines: I did see the uk western link (built to bring wind power from Scotland to England)is 600kv 2.2Gw and there are some active ±320 Kv in europe, and one planned in Italy for ±500Kv

edited to say that now i start looking there's a lot more than i thought; this one in America is ±500kv and was commissioned in 1970:-

https://en.wikipedia.org/wiki/Pacific_DC_Intertie

Adriaan Kragten · « **Reply #14 on:** November 25, 2020, 04:17:52 AM »

Somewhere I have read an article about a very big DC power line lying in the sea from Norway to the Netherlands. It is only a single line and the return current is flowing through the salt water of the sea. So in this case one saves a complete cable. The single cable is built up from many different cables because it appeared that a current has a preference to flow along the surface of the cable and if you use many small cables in parallel, you have a much larger surface than for one massive wire.

Bruce S · « **Reply #15 on:** November 25, 2020, 10:44:45 AM »

I agree with Mab. IF we're to have a discussion on these , then we should define which type of transmission is being used.
DC has losses due to distance which can be calculated for voltage drop. The longer the distance the greater the possible voltage drop unless and larger conductor is used ( less Resistance)
However, as Adriaan pointed out the wire(s) for DC would need to be multi-strand due to the surface flow. These aren't a big issue if say your 48Vdc system is roughly 10Meters away.
I'm pretty certain that doing a search on this Forum (Zubbly ? might have been one) there's been discussions about bringing the wild AC down the pole and then rectifying it to DC to lessen the losses coming from the turbine, or use it as is.

Bruce S

GreenTeam · « **Reply #16 on:** November 25, 2020, 01:51:12 PM »

Quote from: mab on November 24, 2020, 08:40:33 PM

I think there's a bit of confusion about context here:- there's a big difference between transmission from a private windmill to your house and utility scale long-range transmission.

basically, if you want to run electricity over a distance then higher voltage is more efficient.

As Richhagen just said, AC became dominant for utility scale transmission lines due to the ability to transformer the voltage UP for transmission and DOWN for use as required. The problem with AC at high voltage is capacitance of the lines(ironically coming back to the original subject of this thread); this causes the powerfactor to change over the distance and requiring the utility to install powerfactor correction stations which are expensive and waste energy. IIRC 1000km is the rule-of-thumb practical distance limit to HVAC overhead power transmission - you can run longer distance but the PF correction stations and line losses make it expensive - and nowadays it's cheaper to install HVDC. If you're dealing with underground/underwater transmission then the practical limit for AC is ~60km IIRC.

Richhagen - I'm not sure i haven't misunderstood your meaning but HVDC has been around for a while - albeit at <1,000,000V

the following wiki page describes the 1st UK/France HVDC as being commissioned in 1961 (now decommissioned) and the 2Gw ±270Kv bipole replacement was commissioned in 1986 and still in use, along with several others to europe & ireland:

https://en.wikipedia.org/wiki/HVDC_Cross-Channel

There's a link on that page to a whole list of ac and dc transmission lines: I did see the uk western link (built to bring wind power from Scotland to England)is 600kv 2.2Gw and there are some active ±320 Kv in europe, and one planned in Italy for ±500Kv

Actually, if we wanna get to the nitty gritty of why ac won over dc is just good marketing hype. I kinda remember something about an elephant being electrocuted live in public with dc power. And the rest is history. For me, I don't really care , I'll use what ever is the most easiest to implement and with the least amount of hardware. We can always mod the power....

https://en.m.wikipedia.org/wiki/Electrocuting_an_Elephant

Now, ok I'm purty sure I can kill an elephant with ac or dc. But after this date, ac kinda won the game. History yo!!!

Mary B · « **Reply #17 on:** November 25, 2020, 02:56:35 PM »

I remember the debate over this line... and the controversy with towers being dynamited to stop it...

They went DC because it is more efficient for certain distances. It loses to AC after a certain length...

https://en.wikipedia.org/wiki/Square_Butte_(transmission_line)

Adriaan Kragten · « **Reply #18 on:** November 26, 2020, 06:59:48 AM »

Another important difference in between low voltage AC current and low voltage DC current is that DC current is much more dangerous. The advantage of AC voltage is that it becomes zero regularly. I have made hand contact with 230 V AC several times (and even once with 400 V AC). It isn't nice but you can pull away your hand because your nerves aren't blocked when the voltage is zero. But a DC voltage of more than about 40 V may kill you as it might be impossible to pull your hand back.

GreenTeam · « **Reply #19 on:** November 27, 2020, 06:59:14 PM »

lol When I was around 12 my mom asked me to change a light in a lamp stand that had a metal post holding the ceramic light fixture.
Well, the lamp did not survive the day, because, as I changed the bulb I did not pull the plug. As many of us have done millions of times.
But, this lamp post didnt ground properly. And as I rotated the bulb, I wrapped my hand around the base of the bulb onto the metal post.
And than my hand started to hurt. Felt like a sting, a bee sting but all over. Than it slowly went up my fore arm to my elbow.
And than! YEEEEOOOOOWWWW WTF$%^&* IS THAT MOM?!?!?!
my arm really really really hurt. Strangely, I was able to open my hand, which my mom always said to be electrocuted is a losing game because
your muscles will cramp shut leaving you unable to let go of what is harming you.
Luckily, it was only 110V AC in Edmonton.
To this day, I am still scared of some fictures. Especially if they look sketchy and old.

Scary lol

Scruff · « **Reply #20 on:** November 27, 2020, 08:24:22 PM »

I know better than to get involved in politics and religion. Here goes anyways;

DC is safer

& transmits better

Clicky

As regards 115V being safer...

....everything runs hotter with double current for same power. I can touch either...often have (so much so I can tell the voltage ±15V by the bang of it) I know our receptacles fail much less frequently than those across the pond.

Historically AC dominated because transformers are lower-tech than DC voltage converters. Not so much the case anymore with whole cycle viability.

Skin Effect (current travelling along conductor surface areaonly) is an AC phenomenon, DC is not subject to this.

Adriaan Kragten · « **Reply #21 on:** November 28, 2020, 03:09:38 AM »

Okay, I might be wrong. I have only personal experience with touching high AC voltage and not with touching high DC voltage. My explanation of the cramping of the nerves for DC voltage might only be valid for much higher DC voltages than available in small battery systems. Railways mostly use DC current and touching the high DC voltage of an overhead line might kill you directly if you are grounded.

Scruff · « **Reply #22 on:** November 28, 2020, 05:10:36 AM »

>30mA across the heart can kill you. The voltage is a means to inject it. Skin has a resistance ~1kΩ.

400V of either flavour is enough to do serious harm.

Mary B · « **Reply #23 on:** November 28, 2020, 02:01:58 PM »

I know 2 hams who lost fingers to the high voltage DC in an RF amplifier when they contacted 5,000+ volts at 1+ amp...

Scruff · « **Reply #24 on:** November 28, 2020, 02:29:56 PM »

Don't be the fuse.

Bruce S · « **Reply #25 on:** November 28, 2020, 06:30:51 PM »

Scruff, "don't be the fuse is one I'll need to remember :-()

Having survived being the ground to a previously unknown crack in the Bakelite button on a 660Vac I can say it truly truly hurt like nothing before or since (even auto destroying accidents).

The 20,000Vac on a starter cap tingles and serves to remind me to remove the 220Vac breakers to the unit under repair.
12Vdc hurts like he$$ across the elbows.

Having worked with EKG machines and stress test equipment (GE Medical) we use to teach nurses why it was important to "prep" the skin. We would show that dry skin will measure up in MΩ where as sweaty or prepped skin will be down in KΩ. Actually measurable with an Ohm meter.

Mary B
I have a lot of respect for people who work on tube based equipment. NOT my cup-o-tea.

Cheers
Bruce S

GreenTeam · « **Reply #26 on:** November 29, 2020, 02:40:19 AM »

Quote from: Scruff on November 27, 2020, 08:24:22 PM

I know better than to get involved in politics and religion. Here goes anyways;

DC is safer

& transmits better

Clicky

As regards 115V being safer... ....everything runs hotter with double current for same power. I can touch either...often have (so much so I can tell the voltage ±15V by the bang of it) I know our receptacles fail much less frequently than those across the pond.

Historically AC dominated because transformers are lower-tech than DC voltage converters. Not so much the case anymore with whole cycle viability.

Skin Effect (current travelling along conductor surface areaonly) is an AC phenomenon, DC is not subject to this.

Skin Affect is only going to exist due to lack of education or engineering know how, I beleive.
Litz wire, negates skin effect. And, you really dont need to have some god awful high MHz range for litz to do its job.
You can use litz in alternators, especially coreless designs to negate copper losses.
There is a really funky alternator design on youtube by YesEnstein , and he used a home made Litz.
There are many types of litz, from home made audio cables, to high speed alternators, and also low speed alternators.
I am experimenting with litz, simply because I am poor. And I found, by tearing down some house appliances such as microwaves, fans etc
I can acquire 0.15 mm magnet wire, and that, I usually tie on end to a nail in the wall, and walk the wire across the room to a hook.
And back and forth at least 25 times. Than I use a drill and twist it all. Now, I have a home made Litz that is very flexible, and very cost effective.

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Author Topic: Caps (Read 1935 times)