Questions about size of magnetic wire to use

Is there some kind of guideline of what size of magnetic wire to use for induction coils (going off how many amps/volts you expect? For example being able to handle as much as 5KW/h 3 phase AC what would be the best choice? Would 5 phase be able to do it with smaller wire?

I'm also interested on rough estimates of what kind of results the following might be able to get at 500, 1000 and 1500 RPM:

3 phase system 600 turns per coil (possibly only 400) 54 coils total 18 1.5"x1"x0.25" N48 magnets - estimate pull force of ~ 40lbs 10 or 12" diameter rotor (or higher depending on my calculations)

Eric

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ewitte
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An induction coil is a device for supplying spark to auto ignitions. I built one. I used 13 miles of 32 AWG wire in the secondary. Works at about 1 KW . . .

It sounds like you are really talking about an alternator generator or dynamo.

More phases won't make more energy. The advantage of 3 phase is if you're driving AC motors (more efficient) or want to rectify and filter it (less ripple - smaller diodes).

5KW/h sounds like Five Kilowatt Hours? That makes no sense to me, since you could have 5KW for one hour or 50 watts for 100 hours . . .

Yeah that's real precise - 40 lb pull? An alternator is a little more complicated. The spacing between the rotor and stator for instance . . . quality of the iron, frequency, temperature, etc..

There's a wealth of information on the web already

Google for

generator "super magnets"

"brake drum alternator"

There's literally hundreds of thousands of pages on the topic and thousands of people who have practical first hand experience.

40 pound pull? LMAO Heard of Oersteds? Flux density? Gauss? Tesla's?

Kidding aside - throw some of those in as search terms and hit the "brake drum alternator" sites.

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Excellent advice!

Still, I believe it's funny that he was asking originally about "magnetic wire", which is something that I haven't seen since the

1950s... (Magnetic Wire is definitely not the same thing as Magnet Wire.)

Early wire recorders sold during the early 50s (including the Silvertone that my dad owned from Sears and Webster-Chicago) used magnetic wire as their recording medium.

Also, spark and ignition coils (like the Ford Model T spark coils) employed many parallel strands of magnetic wire to form their magnetic cores.

I haven't seen any in use since those days, although no doubt it remains in use for some unique and rare applications.

Harry C.

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hhc314

One do wonder what calculations he's referring to; that would probably be interesting reading.

I've only seen pictures of them. How was the fidelity? and what ips was the wire traveling at? Was the wire malleable or stiff?

I came across and antique store around here that has a stock of old original Model T coils.

I built my induction coil to work as a transformer on 120 VAC and spark coil on 50 VDC. It was used to excite the Tesla coils I was working on. As a transformer I could only get ~6-7 KV out and as and induction coil ~100KV.

I wound one primary on 12 gauge steel wire (stuff used to hang ceilings with - straight 8' pieces in bundles - cut to 18") and a second primary with 20 gauge electric fence wire. Almost no performance difference with the two wire sizes (primary turns the same , secondary turns the same) Primary is 354 Turns X four layers - can be switched into parallel and series arrangements. Secondary is ~67,800 turns (resistance came out to within 300 feet of the design value).

I ran 3 primary windings in series for 120 VAC and all in parallel for DC operation. Took a week to wind the secondary and about 6 months to build the whole thing.

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Yes I'm talking about "magnet wire." For some reason when I type it "magnetic" comes out :) Its for a generator. I'm not talking about more energy from 5 phase. What I mean is could it handle total higher amps? I'm mainly interested in getting help choosing a guage that will not melt or overheat. I would rather not go over 20 AWG cable.

Eric

Reply to
ewitte

That was all I could give you because I could not find the exact magnets. General N48 specs

Gauss rating 13.8-14.2KGs hcb >10.5Koe hcj >11Koe Max energy product 46-48MGOe

Reply to
ewitte

20 gauge magnet wire is small. You can wind more than one wire to increase current.

The current is one thing that determines heating. There's something called "wire tables" that gives some specs on what size conductor can be used for what current. There's also the insulation rating of the wire - some enamels can withstand very high temperatures, some are designed to melt and be easy to solder.

Resistance of the wire to current causes heat, but so do iron losses, and friction. Ambient temperature, and cooling techniques matter.

I use the wire tables from the amateur radio handbook. They are conservative and depending on cooling and surface area of the winding can be "pushed," a bit. 20 AWG is listed at 1.46 amps and that's for transformer construction, and conservative.

Temperature raises the resistance of the wire and lowers the efficiency of the generator.

Power is a function of both current and voltage . . . Like horsepower is a function of torque and speed of rotation. When specifying a generator, you (generally speaking) have some specific voltage in mind and some power level. What is your objective there?

Do you want AC or DC? I assume DC since you don't seem to care how many phases you have. At what current?

Have you checked out some of the on line resources?

AC induction motors can also be used to generate power - and they are plentiful and don't require any work. The output voltage will be a little lower than their design value as a motor, but if your goal is DC or frequency doesn't matter, you can compensate for that with a pulley (sheave) on the motor or source of power. Or just add a small boost auto-transformer to the output.

If my memory serves me - AC induction generators aren't particularly good at starting AC motors - but the information is on the web.

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What about this? Make 54 individual coils. Pair up each three so there is no gap in electricity. After all thats the purpose of 3 phase. So there is always something going on. Then continue over 18 more times. I can use individual diodes with less voltage drop for each output instead of bridge rectifiers. That way wouldn't it be closer to 1.46 amps per coil?

Eric

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ewitte

Right now DC or AC. I'd prefer AC in the future but that makes things a little more complicated.

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ewitte

One big advantage to three phase is "no gap in electricity" as you put it - that translates in an easier to move load, less tendency to "cog," as each magnet moves past a pole piece.

You may want to rethink the diodes. Silicon diodes drop less forward voltage as the temperature rises (if my memory is correct). And you can buy a three phase bridge rectifier if you wanted to.

You should have no trouble getting 1.5 amps per coil. Unlike a transformer, an alternator has some airflow around the coils.

So you plan to have one pair of coils (three amps per phase) span three poles of the stator? With an overlap in coils? (each three offset by one pole, total of 18 poles?)

I notice in a lot of modern motorcycle alternators they rotate the magnets around the outside of the stator. That probably helps keep the wire shorter (use less wire, less wire loss, less heat), shorter magnetic path length (less iron loss, less heat), and since the rotating part has a relatively large circumference, the speed of the magnets passing the pole pieces is higher for the same rotational speed. Looks easier to build the stator that way.

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If each set of three coils is a pole, yes ;) That would put it at 18

3-phase bridge rectifiers. Basically like this except modified so that each set of three coils is off to itself so I'm not putting too many amps through each coil.

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I've been playing around with this kit and have seen about 4-5W at maybe 400-600RPM. Its only 3-4 inches.

Eric

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ewitte

BTW whats the actual best way of using it for actual AC? Ideal would be about 230v AC with a 15a load and about 500-1000W DC load. The 230v

15a load would be used maybe 50% of the time at the most. That would do everything I'm looking for it to do. I'm not sure if a 12" rotor and 18 1.5x1x0.25 N48 magnets would be able to handle that.

Eric

Reply to
ewitte

It looks like a fun project. Ingenious way to form the stator windings.

I don't know that you will really increase the generation capacity by splitting off the coils and treating each to its own bridge rectifier

- I don't know. I just don't see how that changes the power any. I think you'll just have more diodes.

From the design it looks as if you could put another stator at the other end of the turbine, and increase the length of the blades to increase generating capacity.

What really should improve the efficiency would be to put some iron in there.

Looks to me like the only iron is behind the magnets. My guess would be that putting a steel sheet on the side of the stator away from the rotor may increase the output. A better idea would be to (if this is possible) use the stator to form the coils then remove them and pot them in steel filled epoxy.

The steel sheet isn't ideal because it will cause some drag from induced voltages. The thing is . . . iron is something like 800 times more permeable to magnetic flux than air (or plastic etc..). So more flux should be directed to the coils with some iron there to complete the magnetic circuit.

In an AC magnetic circuit (which is your stator) the iron should not be one contiguous piece. That causes induced voltages and drag. (the principle of a car speedometer - a magnet induces a voltage in a piece of aluminum and tends to try to drag it around as the magnet turns - but in the case of a speedo it expends the effort against a spring and moves a needle)

The "eddy currents," as they are called in alternators and transformers, are typically dealt with by using thin sheets of steel oriented in the same direction as the lines of magnetic force (down through the center of the coils). Not too practical in this design.

Some powdered iron mixed with epoxy and put in the centers of the coils should improve output.

Another way to boost the output is to have a second rotor on the opposite side of the stator. The magnets are aligned so that a north on one rotor is opposite a south on the other rotor. That doesn't look easy to do with this demonstration alternator.

That zener diode LED shunt regulator they show looks like a joke to me. If LED's are run at much above 30 milliamps current they tend to have a short life span. A shunt regulator is a good idea - because it will slow the turbine down in a high wind without cooking the storage batteries - but just not that particular design.

And that little "regulator" they show suggests that the current output of this generator is far less than a few amps. If you can get a few watts out of that - you're probably already getting as much as it can do.

Do you plan to scale it up?

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I'm not using completely stock parts. For instance I'm using two bridge rectifiers instead of the diodes. Yes I'm looking at scaling it to 12-20 inches, triple the magnets (5 times the strength each) and triple the coils. The configuration I mentioned was not to get more power off of it. Its to divide the amps out so the thing does not overheat and I could use smaller wire. A huge amount of coils producing 1.5Amps each would be easier to manage than the entire device putting out 54 or so combined off of 3 20 guage wires. Or I could just divide it into quadrants and split it out among 12? That would be easier to manage.

Eric

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ewitte

I just had a fairly interesting idea. What about putting a small strip of iron in each slot underneath each coil?

Eric

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ewitte

worth a try I'd say. It would be better to have some objective way to measure the difference.

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That little rotor is not about to make significant power. You aren't seriously suggesting that are you?

Maybe if it were 500 times larger . . . Think more in terms of car wheel hubs for bearings and 20 foot blades. The rotor itself isn't exactly an aerodynamically clean design. It is a toy - a demonstrator Good for learning not for power.

Look at some of the web sites where people are actually making usable power if that's what you want to do.

Actual AC takes some way to control frequency. The frequency of an alternator is dependant on the number of poles and speed of rotation.

The voltage out is dependant on the number of turns of wire, strength of the magnets (up to the point where the iron can't carry any more flux) and speed of rotation.

The power out is dependant on the voltage and current.

The current out is dependant on the size of the wire.

More or less - there's losses to contend with also.

You don't control the wind. It is not really economical to try to control the rotational speed in small scale wind plants - it only starts to make sense when you have a power grid you want to synchronize to and pump energy into.

Folks that "live off the grid" do so with large storage batteries, and power inverters that can put out the power and frequency they need

- and then they only do it for appliances that require AC - everything that can be run on DC, is.

Folks that live off the grid are obsessive in their desire for self reliance to the point where they would rather sacrifice their comfort for self sufficiency. Or they own a solar cell factory or like to spend money on technology . . . Or they just like to stay far away from "civilization."

A few lucky people with a waterfall in their back yard or geothermal vent are the exceptions. It is cheaper to buy power. (so far).

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I'm not actually talking about wind. They have 100hp AC induction motors for $200 on ebay (probably plus a ton of shipping) and they are seriously nowhere near the size your talking about. Probably 1/4 the size of a car and they put out a ton more than I need. I see people all the time getting ~ 1kw or so with smaller designs. For instance the site I linked to they have a larger 12" version that can get 700 watts or so at under 600RPM. I'm looking at closer to 1500RPM.

Eric

Reply to
ewitte

It sounds like you have 18 magnet poles and 54 stator poles.

for best performance configure the rotos so the magnets altenate north in/ north out, in-out-in-out etc for the 18 magnets

then with the 54 stator poles wind them all the same way and connec them in three series groups a-b-c-a-b-c-a-b-c etc round the stator.

so coil 1,4,7,10... are in series and 2,5,8,11 and 3,6,9,12 etc

then you'll want a three phase bridge rectifier .-->|-A->|--. | | --+-->|-B->|--+-- - | | + `-->|-C->|--'

Bye. Jasen

Reply to
Jasen Betts

if it's a wind turbine it's unlikely to produce usable AC. convert it to DC and use an inverter

Bye. Jasen

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Jasen Betts

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