affect of dual vs single rotor

[defed]

let's presume i have a set of coils and running a single rotor, what affect does adding a 2nd rotor have?  is only the voltage increased or also the amperage?

seems this should have been an easy answer to find, but i've been searching for awhile w/ no luck!

thanks!

[Mary B]

Only increase voltage(doubles) if you run them in series, current stays the same, in parallel it is the same voltage but double the current

[defed]

thanks, i was thinking only voltage changed....but i'm a little confused on the part about series vs parallel.  are you referring to how the coils are wired up?

for my experimental setup, i have a single phase stator, 4 coils wired in series.  i am running a single rotor.  i used pretty fine wire, not knowing what i wanted to do - to get a baseline...i get plenty of voltage, just not many amps.  so before i wind some coils w/ thicker wire, i was wondering what adding the 2nd rotor would change...and that is only to increase voltage.  but knowing that may affect how i proceed w/ the new coils.

[MattM]

If you have three phases each 'stator' then adding a second stator gives you six phases.  Phases all tied in serial would be double voltage for a single phase.  (e.g. 2v * 6 = 12v)  Or run each stator as a single phase to double amperage, but across two phases.  (e.g. 2v * 3 = 6v * 2)  Or you could run each paired opposing phases in serial would be double amperage for each of three phases.  (e.g. 2v * 2 = 4v * 3)  Or you could run each phase as standalone to simply have six phases.  (e.g. 2v * 1 = 2v * 6)  Do ask yourself if you want 1, 2, 3 or 6 phases.

Or if you like wobble, run the phases from one stator out of phase with the opposing stator and mismatch phases so its imbalanced.  Or run something like four phases (serial or parallel) separate from the remaining two phases (serial or parallel).  Some people are wired to do crazy stuff like that.

[defed]

right now, i have 1 stator, single phase, and 1 rotor.  what i wanted to know is what happens to the output of the stator when adding a 2nd rotor (everything else staying the same -  rpm, stator wiring).  if i get 30v and 1 amp now, adding another identical rotor will do what.....60v and 1 amp?

as i don't understand how to design a stator to do what i want, i am experimenting and just winding some coils.  then i will attempt to adjust and tune it to where i want to be.  this is axial flux.

[electrondady1]

with a single rotor the magnetic flux is moving from one magnet to the next.  and not cutting through the coil at 90 degrees.
with two rotors the flux travels from one rotor to the other and cuts through the coils at 90 degrees. the flux density is more than double.
the voltage and the amperage is going to be increased.

[defed]

with a single rotor the magnetic flux is moving from one magnet to the next.  and not cutting through the coil at 90 degrees.
with two rotors the flux travels from one rotor to the other and cuts through the coils at 90 degrees. the flux density is more than double.
the voltage and the amperage is going to be increased.

is there a general rule as to what degree they increase?  do they both double?  does voltage double and amperage by 20%?  i'm sure there are many factors, but just looking for a rough idea so i know what to aim for in my next test coil.

[SimonMester]

with a single rotor the magnetic flux is moving from one magnet to the next.  and not cutting through the coil at 90 degrees.
with two rotors the flux travels from one rotor to the other and cuts through the coils at 90 degrees. the flux density is more than double.
the voltage and the amperage is going to be increased.

Why don't they employ the same double rotor idea for radial machines then?

[electrondady1]

when flux density is increased  the voltage will rise.  if your looking for a specific voltage then the number of turns can be decreased or the conductor diameter can be increased to reduce resistance.
in a radial the coils are usually embedded in iron that pulls flux through the  coil. you could build two rotating cylinders of magnets  but that becomes tricky from a mechanical standpoint.

[defed]

right now, i'm just experimenting.  i don't have specific voltage in mind, i just made a coil because i had no idea where to start.  i used 30awg because the magnets/coils are small, so i figured i needed thin wire to get any voltage.  i ended up w/ ~7.5 volts per coil (x4 in series), so 30v open circuit.  i have a little test motor, running around 1600rpm on 4w.  to test the power of the alternator, i used some leds.  each led is 3v and 20ma.  i start my motor, get the stator close to the rotor, put 1 led into my breadboard and the thing bogs right down to a stop.  amps spiked at maybe 300ma.  i'm thinking, there's no way this thing can't run ONE led!  i figure out that i have to move the stator away from the rotor, then it's working fine.  i can keep adding leds, in series and parallel (again, to experiment and try to figure out what it can output) and the more i add the closer i move the stator to the rotor...i can have 25 leds running fine, but if i put one led in so that only it draws the load, the same thing happens, it spikes to 300ma and bogs down....interesting that it can run 25 in a certain configuration, but not one (i don't fully understand what is happening there).  i seem to recall from the windmill books that you have to tune your coils to what you are trying to run, so i presume that is what is happening when i have to adjust the gap between stator and rotor, and that a certain gap for certain loads works.  i figure at best i'm making .5w.   so now, i think i want less voltage and more amps, so i'm going to try thicker wire....but if i know what a 2nd rotor will do, i can afford to go for less voltage if i can double it later w/ another rotor.  one other thing i know is hindering output is, i don't have a steel backing on my rotor.  i am probably losing a lot because of that.  my little test motor is on magnetic bearings, i still have to test how much weight it can bear before trying to add something there.

yes, i have no idea what i am doing, but i figure the best way to learn is to play around and see what happens.  just looking for some basic guidelines to point me in the right direction.

[Mary B]

right now, i'm just experimenting.  i don't have specific voltage in mind, i just made a coil because i had no idea where to start.  i used 30awg because the magnets/coils are small, so i figured i needed thin wire to get any voltage.  i ended up w/ ~7.5 volts per coil (x4 in series), so 30v open circuit.  i have a little test motor, running around 1600rpm on 4w.  to test the power of the alternator, i used some leds.  each led is 3v and 20ma.  i start my motor, get the stator close to the rotor, put 1 led into my breadboard and the thing bogs right down to a stop.  amps spiked at maybe 300ma.  i'm thinking, there's no way this thing can't run ONE led!  i figure out that i have to move the stator away from the rotor, then it's working fine.  i can keep adding leds, in series and parallel (again, to experiment and try to figure out what it can output) and the more i add the closer i move the stator to the rotor...i can have 25 leds running fine, but if i put one led in so that only it draws the load, the same thing happens, it spikes to 300ma and bogs down....interesting that it can run 25 in a certain configuration, but not one (i don't fully understand what is happening there).  i seem to recall from the windmill books that you have to tune your coils to what you are trying to run, so i presume that is what is happening when i have to adjust the gap between stator and rotor, and that a certain gap for certain loads works.  i figure at best i'm making .5w.   so now, i think i want less voltage and more amps, so i'm going to try thicker wire....but if i know what a 2nd rotor will do, i can afford to go for less voltage if i can double it later w/ another rotor.  one other thing i know is hindering output is, i don't have a steel backing on my rotor.  i am probably losing a lot because of that.  my little test motor is on magnetic bearings, i still have to test how much weight it can bear before trying to add something there.

yes, i have no idea what i am doing, but i figure the best way to learn is to play around and see what happens.  just looking for some basic guidelines to point me in the right direction.

LED's do not like more than 3 volts typically(some 1.5ish!) so you are shorting it out

[defed]

hmm, that does make sense as it acts similar to shorting the stator (as is done to brake windmills).  LOL

guess i never knew that would be the result of too much voltage to the led.  i was very confused as to what was happening.

[Bruce S]

defed;
Depending on where you're located USA or EU do a search for AWG or M2 wire to find the max current handling abilities.
Thin wire will give you a higher voltage while thicker wire will give you a higher current.
We have a FAQ section that will help you a ton in understanding the interactions of the two. It can certainly help in understanding serial vs parallel.

Cheers
Bruce S

[defed]

defed;
Depending on where you're located USA or EU do a search for AWG or M2 wire to find the max current handling abilities.
Thin wire will give you a higher voltage while thicker wire will give you a higher current.
We have a FAQ section that will help you a ton in understanding the interactions of the two. It can certainly help in understanding serial vs parallel.

Cheers
Bruce S

yes sir, i am aware of current capacity of wires, though more as in residential gauges rather than these small magnet wire sizes.  i do know that thin wire gives more voltage, that's why i started thin, because i wasn't sure what i could even get from this tiny alternator.  and i've also read that there is no real formula for designing coils...mostly trial and error.  so now that i know what voltage/current i am at, i can adjust from there.  i just wanted to know what affect adding a 2nd rotor has, if it doubled both, that's one thing.  if it just doubles voltage, well, i can theoretically design my coil to make half the voltage i am after and chase amps and then add that 2nd rotor.

[defed]

now that i've established a baseline...i get this much out of this wire, this many turns, this rpm....is there a way to determine what different wire sizes will achieve w/o actually winding every wire gauge and testing?

ex:  30awg gives me this result.  using that info, i can calculate that 26awg will do this, 23awg will do this, etc.

[Bruce S]

As I stated earlier the FAQs section has a ton of info,even a wire calculator  .
Here's a link that I found in there.
https://fieldlines.com/index.php/topic,143174.0.html

Bruce S

[MagnetJuice]

Hi defed,

i do know that thin wire gives more voltage, that's why i started thin, because i wasn't sure what i could even get from this tiny alternator.

A thin wire does not give more voltage. It is true that for the same coil size, you can get more turns with thin wire. Voltage is determined by the number of turns, not wire thickness.

let's presume i have a set of coils and running a single rotor, what affect does adding a 2nd rotor have?  is only the voltage increased or also the amperage?

As others have said, adding a second rotor will increase both voltage and amperage. In other words, it will increase power (watts).

Here is an example:

The 4 foot machine from Hugh Piggott's book will produce 26 volts with 155 turns per coil, at 300 RPM.
If you add another steel disk without magnets, it will produce 38 volts. If you place magnets on the second disk, it will produce 54 volts. All with the same 155 turns per coil and at the same 300 RPM.

What are you planning to do with the power after you build your final alternator?

Ed

[defed]

Hi defed,

i do know that thin wire gives more voltage, that's why i started thin, because i wasn't sure what i could even get from this tiny alternator.

A thin wire does not give more voltage. It is true that for the same coil size, you can get more turns with thin wire. Voltage is determined by the number of turns, not wire thickness.

let's presume i have a set of coils and running a single rotor, what affect does adding a 2nd rotor have?  is only the voltage increased or also the amperage?

As others have said, adding a second rotor will increase both voltage and amperage. In other words, it will increase power (watts).

Here is an example:

The 4 foot machine from Hugh Piggott's book will produce 26 volts with 155 turns per coil, at 300 RPM.
If you add another steel disk without magnets, it will produce 38 volts. If you place magnets on the second disk, it will produce 54 volts. All with the same 155 turns per coil and at the same 300 RPM.

What are you planning to do with the power after you build your final alternator?

Ed

yes, you are right, turns = volts, not wire thickness....but as you also said, you can fit more turns of thinner wire onto a given coil....so while i was technically 'wrong', i know what i meant...but i should state it accurately!

when you say dual rotors increases the watts...yes, increasing either volts or amps will increase wattage....in your example, the 4' goes from 26v to 54v, which is more than 2x voltage, and wattage, (unless you made a typo), so do the amps actually increase as well, which would more than double the output?

i have no idea what i'm going to do...charge a battery probably, but i'm so far from that as i'm still just testing the feasibility of even turning an alternator.  i still haven't gotten around to trying different wire for my coils yet.

[MagnetJuice]

(unless you made a typo), so do the amps actually increase as well, which would more than double the output?

No, I didn't make a typo and yes, the amps will increase as well.

Let’s say that your alternator's open voltage (no load), is 36 volts and you are charging a 24 volts battery. The battery is going to clamp the voltage at 24 volts, or a bit higher. You had 36 volts and now you have 24. What happened to the other 12 volts? They went into the battery as amps.

Ed

[defed]

that's one thing I need to figure out, how to 'tune' the alternator to the load.  i made a single rotor 4' turbine quite a few yrs ago (15+), so it's been a long time since i worked on an alternator.  i remember the concepts of open voltage vs charging voltage, cut in, stall, etc but i don't remember how to figure it all out.  for example, if i want to charge 12v batteries, it almost seems like, hey, if i have 60v open, that HAS to be better, right?  that gives me plenty of 'extra'... but i don't think it's a matter of making the most possible.