Effects of Recirculating BEMF to Coil

[cody]

I'm not sure about it holding the magnetic field longer, since if I hold the magnet down on the coil you can feel many more time the push up compared to no re-circulating. So it appears to strengthen the magnetic field.

Luc,
I think you could easily prove or disprove with a gaussmeter weather the field is actually stronger. I think some people even use clamp on amp meters as an indication of field strength. Not sure how the pulsing would effect the measurments though But that is defiantly an important question that should be understood. Peters comments are very incouraging

[SkyWatcher]

Hi folks, Hi Luc, I ran a test with an air-core coil with the dimension ratios of a brooks coil using 18 gauge pulsed with 555 using a 12v battery. Using 1" dia. neos for testing, when using the flyback diode there is definitely more lift on the magnet, however I'm not sure how extended duration of coil field could account for that, though I see why Peter would say that. But the results seem to say that the magnetic field is stronger to me, unless a longer duration field at same intensity can account for that, I'm not sure and only some kind of Gauss meter test would prove it.
peace love light
Tyson

[poynt99]

See these references Luc...

Luc:

Quote from: poynt99 on July 04, 2009, 11:36:34 PM at OU.com
Luc.

In my tests I've confirmed all your findings, except the magnet elevation, but since the magnetic field in a coil is proportional to the current through that coil, I think it's safe to say that is covered as well.

What you've built is essentially a DC-DC converter. You've taken a high voltage low current source and converted it to low voltage / high current in a load. In this case the load and conversion element are one in the same, the coil. The diode completes the appropriate circuit path that allows the conversion to actually take place.

Some numbers I obtained from my tests:

Ave VS Ave IS Ave WS Ave VC Ave IC Ave WC
Without Diode: 170V 15.5mA 2.635W 157mV 15.5mA 2.43mW
With Diode: 170V 10.6mA 1.802W 2.932V 285mA 0.836W

Where:
VS = Supply Voltage
IS = Supply Current
WS = Supply Power
VC = Coil Voltage
IC = Coil Current
WC = Coil Power
(these are averaged values)

Indeed the current from the supply decreases with the diode in-circuit, but the output power from the coil never exceeds the input from the source.

Notice the huge increase in coil current with the diode in-circuit compared with it out of circuit? This explains the force it has on your neo magnet. With coils, it's all about current. A substantial amount of power has been transferred to the coil with the diode present (about 46% of the input), as opposed to nearly none without the diode.

Are there any gains in power or energy? No, in fact there is quite a substantial loss due to the DC resistance of the coil and connecting wires.

I hope this explains all that is happening with your experiment, but I'd be happy to expand on or run tests on any aspect if you want. Scope shots are also available if you wish.

Regards,
.99

Quote from: poynt99 on July 06, 2009, 12:22:34 PM at OU.com
Hi Luc.

Monitoring a coil's voltage does not always indicate what is going on there in terms of its current. The fact that the bottom portion of the coil voltage disappears when the diode is in-circuit, actually does indicate that a conversion is taking place. The conversion is from high voltage/low current, to high current/low voltage. If you zoom in when the diode is in-circuit, you will probably see a negative swing of about -0.65 Volts (from the previous -300V or so), but the current has shot up significantly. This is the indicator that "something" different is happening in the coil that is causing the increased magnetic power.

With no load (i.e. without a flyback diode), the coil sees almost an open circuit during its inductive kickback cycle. The same amount of energy (minus losses) must be conserved, so the coil voltage extends quite high in the reverse direction, but the current is quite small.

When the coil IS loaded during its inductive kickback cycle by placing the diode across it in reverse, the diode creates nearly a short circuit across the coil during this cycle, so the current has no choice but to increase by a large amount. It is this increase of current that you can not see by looking at the coil voltage, but this increased current is what is responsible for the much larger magnetic force being applied to your neo magnet.

Remember with coils, it is current that energizes them and produces a corresponding magnetic field, not voltage. With a heavy enough wire you could produce quite a strong magnetic field with only a few volts, as long as the source can supply a large current.

Hope that helps,
.99

and with the document:
Effects of Recirculating BEMF to Coil
or
http://www.energeticforum.com/60397-post73.html

Peter L. is the only one that is somewhat close so far, but not quite. It's simple: Adding the flyback diode causes the inductor current to be "rectified", similar to how voltage is that's used to charge a capacitor. Because of this rectified current, the average, or mean current in the inductor increases substantially, and as such, so does the magnetic force from the coil which kicks the magnet. Remember also that the flyback diode helps convert voltage to current, which is what is needed for a stronger mag field. See the comparison of the coil current wave forms at the end of the document.

.99

[SkyWatcher]

Hi poynt99, you said quote "Remember with coils, it is current that energizes them and produces a corresponding magnetic field, not voltage. With a heavy enough wire you could produce quite a strong magnetic field with only a few volts, as long as the source can supply a large current."
This is not the complete truth, my experiments show that as Joseph Newman states that current is a catalyst, the magnetic field comes from the wire. Take 1 turn of say 18 gauge and at a certain current input, adding any more current above a threshold does not give more magnetic field it just gives heat. So this simple test proves that the magnetic field from a coil of copper wire is a function of the wire not solely current. Thought that needed to be said because I notice this theme of folks trying to distort whats really happening within a coil of wire.
peace love light
Tyson

[poynt99]

Tyson,

Indeed this may happen. It all depends on the wire.

What happens to the characteristics of the wire as it heats up? (Hint: this is not a rhetorical question )

.99

[SkyWatcher]

Hi folks, You may answer your own quiz questions for us poynt, I'm not playing those games, though i do know what your getting at. Anyway here is a circuit that may work to switch in and out the flyback in a motor configuration, though a commutator would work also if the motor geometry were simple, like for proof of principle, 1 or 2 magnets on a rotor would make for a simple commutator build. Not sure if just using a straight reed switch would hold up.
peace love light
Tyson
edit forgot circuit pic

[SkyWatcher]

here is a pic of the circuit.

[Inquorate]

Tyson,

Indeed this may happen. It all depends on the wire.

What happens to the characteristics of the wire as it heats up? (Hint: this is not a rhetorical question )

.99

The wire heats up and resistance increases.

[SkyWatcher]

Hi folks, thanks inquorate for filling in the quiz box. I would hope we all can have a conversation without playing the know it all game or i think i know more than you, because that is one reason the world is the way it is. Now, my idea of what this threshold means is the same thing that happens to a permanent magnet when heated to i believe the curry point. its the same in a wire, no matter the thickness. It may be similar to what happens to water at the threshold point between it turning to ice. Though I'm more concerned keeping on topic with what Luc is doing.
peace love light
Tyson

[poynt99]

The wire heats up and resistance increases.

So Tyson or anyone, I would very much like to hear why this does not adequately explain the tapering-off of the increasing mag field as one attempts to increase the current in a wire that begins to heat up?

The current has a tendency to self-regulate, very much like it does in an incandescent bulb.

Why the attitude towards me Tyson

.99

[SkyWatcher]

Hi folks, Hi poynt, no attitude, just not thrilled with quizzes and the superiority complex that it conveys. I know nothing compared to what I dont know and I'm sure that lack of knowledge is vast beyond my comprehension at this point, therefore I try to keep an open mind. I understand resistance increases but my thought is that it's more of an effect not the fundamental cause, maybe like when ice turns to water or vice-versa it may be a thermal change which is the effect however its an operation intrinsic to the matter itself that is the cause and thats what I'm getting at. It may seem like a gradual blending threshold but at some point it is like a switch turned on or a flipping similar to magnetic domains flipping and we have ice crystals forming. I hope this makes more clear what I'm trying to convey as to my thoughts. Its all good.
peace love light
Tyson

[cody]

poynt99,

I never thought of it like that but i think you are right. The collapsing field comes out at a higher voltage than the original applied voltage. So the higher collapsing voltage applied back into the coil would convert into more amps than the original amps(just in a shorter time frame i believe). More amps means stronger magnetic field Very good thinking, but it should still be tested

[SkyWatcher]

Hi folks, here is my take on it after some thought and poynt's thoughts. We may get a higher intensity magnetic field initially to boost the magnet up higher then as the coil rings back and forth through the diode it gives a progressively less intense magnetic field until next primary pulse. Therefore I think this is why Peter L. said what he did, that the magnetic field's duration is extended and this may explain what he was getting at and how at the same time the fields intensity is boosted and its duration. let me know what ya folks think. Its all good.

Tyson

[SkyWatcher]

Hi folks, Hi Luc, just wondering how the experiments are going and if you've got the test bed device up and running yet whatever it may be.
peace love light
Tyson

[gotoluc]

Hi Tyson,

thanks for your interest

I spent many days building a a very complex relay switching timing system (6 relays) to operate my small dual MOT secondary coils motor with rotating PM in the center. I found the re-circulating diode effect only works with capacitive discharge of low uf but higher voltage then one would normally use to operate a motor. It comes to the same thing as very short duty cycle and higher voltage.

It looks like a trade off, as if I run it with strait DC it will run at a much lower voltage and the re-circulation diode has no effect at these voltages and if we add up all the watts numbers I seems to be more efficient with strait DC then with capacitive discharge or short duty at higher voltage.

Most likely this is what .99 was explaining. Unfortunately I am self tough, so I don't understand these common educated explanation and graphs! it just goes over my head ... I need to do an experiment to come to understand. So if you're reading this .99!... please make a point to keep this in mind for next time and save yourself allot of writing. All you need to do is think of an experiment I can do to make me see what you want to explain.

At this time I'm presently working on an effect that I found a while back when I was working with resonance and will soon make a new video and topic to share and see if it has any value to continue to research.

I'll post the link to the new topic when I start it.

Thanks for all your interest

Luc