Increasing coil out-put

[artv]

Hi All,...I've read alot of postes here ,on various topics , but haven't seen anything about boosting coil out-put at the AC side ....
No rectifiyers, caps or transformers,....just the AC straight from the coil??
If the coil (a single coil) puts out 1/2 a volt AC (.5VAC) at 200 rpm ,....the bridge will absorb all the available voltage (due to the diodes .7volts drop) and the result will be O volts DC.............is this correct??........artv

[RP]

Not really "absorb".  Just not enough voltage to switch the diode on but yes, zero volts output.

[rossw]

Hi All,...I've read alot of postes here ,on various topics , but haven't seen anything about boosting coil out-put at the AC side ....
No rectifiyers, caps or transformers,....just the AC straight from the coil??
If the coil (a single coil) puts out 1/2 a volt AC (.5VAC) at 200 rpm ,....the bridge will absorb all the available voltage (due to the diodes .7volts drop) and the result will be O volts DC.............is this correct??........artv

Well, duh! Thats why we wind more than one turn. If one turn makes 0.2V (not enough to use generally), then 10 turns wound the same way will make 2V, and 50 turns makes 10V.

No electronics, no trickery, no smoke and mirrors, nothing to fail with EMP or lightning. Insulated properly and wound carefully, it'll last near enough forever...

[Flux]

"If the coil (a single coil) puts out 1/2 a volt AC (.5VAC) at 200 rpm ,....the bridge will absorb all the available voltage (due to the diodes .7volts drop) and the result will be O volts DC.............is this correct??........artv"

That is only part of the problem, even if you get over the rectifier drop, what use will it be. Even a led will need another volt and a half to light and similar for a single cell.

I really don't follow all this confusion, you can get as many volts as you want out of a coil by increasing the turns, why boost it. You can connect more coils in series to do the same thing.

What is far more confusing is the difference between having enough volts and enough power to do something. You can boost volts by many methods but they invariable restrict the amps available, you can't boost power. If it is only the lack of volts that is causing your trouble then there are many ways round it but for a given speed, magnets and copper there is only so much power available. The best you can do is match it to the load in the best way.

Flux

[electrondady1]

optimizing the output of each coil is a worthy area of exploration.
with lots of different directions to go .
as flux has said it's relatively easy to get the volts you want.
 but its tough to get amps
it comes down to geometry i think

[artv]

Thanks for the replies.....I'm not being very clear I guess
RP......so at 200rpm ( .5VAC) after rectification I should not be able to charge my parallel 56volt ,12000uf caps?

Ross....when I said single coil ,I didn't mean a single turn of wire....the coil is 36 turns of,.. I think 1.2mm wire
I measured it with a tape..."nothing to fail with EMP"...I don't know what that means???
Flux..."you can get as many volts as you want out of a coil by increasing turns".....by doing that you also increase resistance right??....and that lowers the amps out?
E1..."worthy area of exploration"....I've been trying various coil configurations.....I'm still testing , but was able to increase the output of the coil above from 1/2VAC  at 200rpm to off the scale on my meter(200VAC)....and it does charge up my caps.
Just for fun I tried a big primary out of a micro-wave transformer, with no metal behind it and it charged the caps even faster...
I added a bifilar winding to the top of the coil , to get these results...the big primary was off the scale of 250VAC....but the volts on the other side of the bridge were still low.......The bifilar coil does boost output......artv

[rossw]

Ross....when I said single coil ,I didn't mean a single turn of wire....the coil is 36 turns of,.. I think 1.2mm wire (Attachment Link)
I measured it with a tape..."nothing to fail with EMP"...I don't know what that means???

Ahh. ok. Wasn't clear.
EMP is "Electro-Magnetic Pulse". I was thinking in terms of complex device(s) to boost the output and their susceptibility to damage.

I added a bifilar winding to the top of the coil , to get these results...the big primary was off the scale of 250VAC....but the volts on the other side of the bridge were still low.......The bifilar coil does boost output......

Odd, bifilar windings are generally wound such that they're "non-inductive" - which also means they shouldn't have any appreciable voltage induced in them in the presence of a magnetic field, so I don't see the mechanism by which one will "boost output" at all.

As for your comment that "additional turns = additional resistance = less current"..... well, yes, but lets not forget that if the voltage is so low you get nothing out the bridge, you already have "no current" so even a small current is better than no current

There are basically a few variables. For a given coil that means its number of turns and physical dimension is a constant, you can increase the output voltage by:
 * adding additional complete coils in series (in phase)
 * increasing the rate of change of the magnetic field
 * reducing the load (obviously not a consideration in unloaded coil tests)

Increasing the rate-of-change of the magnetic field could be done by increasing the relative speed of the movement between the coil and magnet, or by making the magnet stronger, or by interspercing additional magnets of alternating N/S alignment, or a combination of the above.

At a theoretical (rather than practical) level, confining the magnetic field into a narrow beam would allow for a substantially higher rate-of-change of flux density and therefore higher voltage, but over a proportionally reduced time, making high voltage pulses. Probably the same *power* output (watt-seconds) and *average* voltage, so I can't see where you get an advantage.

[rossw]

(due to the diodes .7volts drop) and the result will be O volts DC.............is this correct??

Some low-voltage machines use schottky diodes which have lower forward voltages.
Some machines use synchronous rectifiers which have very very low forward voltage drop (but not suitable in this application - they use the very low voltage drop to reduce heat generation rather than permitting them to produce very low output voltages)

[artv]

Just getting here now,..Hi Flux ,"you can boost volts", " you can't boost power"......the more power you have the faster you can charge a capacitor??.....Less will only charge so high,...then come to a rest at a certian voltage..............Thanks for the replies'.....artv

[seilertechco]

I've been researching the use of permanent magnets combined with electromagnets.  Seems that there is a way to make it either stronger, weaker or just the force of the permanent magnet to explore that can work by having no exciter voltage or changing from + to - .  I want to do more in this area. 

Toby

[MattM]

Sorry to resurrect an old thread, but this Youtube video demonstrates bifilar coils in an axial PMG rig.