Effects of Recirculating BEMF to Coil

[gotoluc]

Hi Jetijs,

thank you for your positive comment

You are the best also you are always there willing to help and replicate to verify anyone's findings. Your contribution to this Forum is most outstanding



Luc

[Shamus]

Hi Luc,

I'm pretty sure that you don't need AC pulses to get into resonance, you just need *pulses*. From what I understand, it seems like both circuits you showed in your videos (awesome presentation, BTW ) are very similar to what occurs in Ms. Ainslie's circuit, no?

[Tecstatic]

Resonant mode would be interesting but since motors run at such low frequency I would be surprised we can get an air core coil to resonate.

To my understanding you can get resonance 2 ways:

1. applying a periodic signal at the resonant frequency
2. applying a single pulse of the right pulse width.

So even if the motor runs slowly, you can make low inductance coils with short time constants at the drive voltage, so at max revs you maybe have 10 or more pulses per pole passage.

This way you run in resonant mode.

You can maybe have the problem that the inductance is angle dependent, then a single pulse with is not enough.

In that case you have to add a high resolution encoder to the motor and let a micro controller read the angle from the encoder and from that and other factors determine the pulse with which triggering resonance.

Yes, I know some will say this is over complicated, but if you want much more efficient running with non-constant inductance, it may not be for free (a small simple circuit).

Eric

[Hoppy]

@ all

There is an important thing to understand about a charged coil / inductor being shorted via a series connected diode. At switch closure, the discharge pulse although very short in duration, is very high in current and governed by the total loop resistance which includes the forward resistance of the diode. The magnetising effect of the resulting and rapidly changing magnet field around the coil, is sufficient to levitate the magnet sitting above the coil pole piece. There is ample time for the magnet to respond to this field because the duty cycle of the applied pulse to the mosfet allows a very long 'off' period compared to its very short 'on' period. In contrast, given that time is needed to fully charge the coil, the resulting magnetic field created by the mosfet switching 'on', is insuficient to levitate the magnet to the same extent as the coil discharge field. This is why I think a difference can be seen between the switch open and closed states. The test of this is to run the mosfet at a 50 / 50 duty cycle and compare the distance of levitation between switch 'on' and 'off' states.

The level of current in the coil discharge will depend on the resistance of the closed loop. In this almost short circuit loop back situation, the discharge current pulse will be extremely high reducing the instantaneous high discharge voltage to almost zero (+0.6V ish for the forward voltage drop of the diode) very rapidly. This is in effect an energy conversion process from pure potential to an electron current flow. If the coil discharge pulse is applied to a battery instead of being shorted back to the coil, the discharge current pulse will again be very high and determined by the total loop resistance including the internal resistance of the battery and forward resistance of the series diode.

Hoppy

[baroutologos]

ok, guys something i do not get i suppose.

1) Coil idle
2) Coil gets energized (current gradually increases)
3) Transistor cuts off current
4) Coil's magnetic field collapses, energy stored there is realeased
5) Current starts to flow as a current and voltage spike
6) Re-formulation of magnetic field ????
7) This also has to collapse???
8) Fractal diminishing effect???

Pls explain.

Regards,
Baroutologos

[Hoppy]

ok, guys something i do not get i suppose.

1) Coil idle
2) Coil gets energized (current gradually increases)
3) Transistor cuts off current
4) Coil's magnetic field collapses, energy stored there is realeased
5) Current starts to flow as a current and voltage spike
6) Re-formulation of magnetic field ????
7) This also has to collapse???
8) Fractal diminishing effect???

Pls explain.

Regards,
Baroutologos

The magnetic field created whist the inductor is charging, disapears when the mosfet switches 'off'. The energy stored at this point is then released through the diode because the polarity of the coil reverses. There is therefore only one charging event and one discharging / field collapse event per applied pulse to the mosfet. When the switch is open / 'off', then the coil will still discharge through the lowest resistance path it can find but this could well be across the mosfet switch itself, if the voltage rating of the mosfet is insufficient to prevent breakdown. The higher the resistance of the discharge path, the higher will be the voltage developed across the mosfet. Here we have a transfer of energy in high voltage form, seeking a path to circuit ground in order to convert into electron current flow in order to dissipate. If this energy is unable to dissipate quickly enough through a leakage path between mosfet pulse cycles, then the inductor will become saturated and subsequent cycles will result in less current being switched through the inductor and the discharge voltage rising until it finds a level where an available leakage path allows the voltage to stabilise. The effect of this on the magnet should be as is observed, where the current in the coil whilst the switch is open, is insufficient to levitate the magnet very far in comparison to when the switch is closed.

Hoppy

[baroutologos]

The effect of this on the magnet should be as is observed, where the current in the coil whilst the switch is open, is insufficient to levitate the magnet very far in comparison to when the switch is closed.

I thought guys here are stating the exact opposite thing.

Nevertheless, you say in off mode, the current flow stops, magnetic field dissapears and the stored energy (in magnetic field) re-enebles current flow.(secondary one or volatge/current spike as we know it)

This in turn you say, it does not create any magnetic field, right?
Or the spike has not any mechanical effects (since it does not create a secondary magnetic field) right? Irrelevantly if electrons move also this time. (???)

I do not know, very confusing.

Regards,
Baroutogos

[Hoppy]

I thought guys here are stating the exact opposite thing.

Nevertheless, you say in off mode, the current flow stops, magnetic field dissapears and the stored energy (in magnetic field) re-enebles current flow.(secondary one or volatge/current spike as we know it)


This in turn you say, it does not create any magnetic field, right?
Or the spike has not any mechanical effects (since it does not create a secondary magnetic field) right? Irrelevantly if electrons move also this time. (???)


I do not know, very confusing.

Regards,
Baroutogos

Taking your comments in turn: -

I'm referring here to the mechanical switch. When the mechanical switch is closed, the magnet levitates to the greatest height.

Yes, when the mosfet is 'off'. Current is then able to flow through the diode if the mechanical switch is closed.

When the mosfet is 'off' no field exists around the coil. It is only re-established when the mechanical switch is closed and current is allowed to flow from the discharging coil. Current has to flow in order to create a magnetic field. The inductor holds a charge when open circuited as does a capacitor.

Hoppy

[gotoluc]

Hi everyone,

I have made a new video with a better quality camera I now have for all future videos.

I made this new video because something was bothering me about my previous conclusion using my good quality meter to measure the Watts Energy of the pulsing circuit compared to using straight DC. I talked to my Engineer friend and he has confirmed to me what I was thinking. Watts energy has nothing to do with Voltage since you can have thousands of volts going through a resistor and there could be no heat if there is no Watts energy. So Watts energy should be measured by heat dissipation at the Resistor regardless of the voltage.

So what I'm getting at is, since it's so difficult to measure the Energy used by these kinds of circuits lets just measure the heat dissipated in a resistor at the input of the circuit compared to the heat dissipated at the output.

I have redone a video using a visual restive load on the input with the circuit functioning with an 8% duty cycle to compare it using the same load with straight DC and the results are quite different then what my quality meter was calculating.

I know many will be saying that this is not the way to measure. However I'm not measuring! the bulb is only a visual display of Energy and nothing else regardless of the voltage going through it because it's resistive.

Also note that I will be redoing the test over but using standard resistors and measuring the heat dissipated at the input compared to the heat dissipated at the output and posting the video next week at some time. In the meanwhile this gives us something to think and talk about.

Video link: YouTube - Effect of Recirculating BEMF to Coil test 3

Luc

[Shamus]

Hi Luc,

I just watched your video #3 and all I can say is "WOW".

I like where you're going with this.

[gotoluc]

Hi Shamus,

thanks for your positive post

Looks like Inductive kickbacks can create lots of heat

Hard to believe that all that output heat Energy is capable of going through that tiny filament bulb without producing any heat there

I though there would be more comments on this video by now

Luc

[mklimesh]

Hi Luc


Great video, shows exactly what Rosemary is saying on the
COP 17 Heater thread, excellent job.

Mike Klimesh

[gotoluc]

Thanks Mike

as you may know the video is posted there also and Rosemary is fine with discussions about the circuit in her topic: http://www.energeticforum.com/renewa...html#post59813 and it maybe easier for everyone.

Thanks again for your positive comment

Luc

[Hoppy]

Luc

Great video well presented. In the pulsed setup you had a low brightness bulb and two very hot resistors. In the DC model you had a very bright bulb with not so hot resistors. How does the total heat radiation in the circuit for both setups compare? The heat in the coil should also be taken into account. A comparison of the total circuit energy to heat conversion in both models is essential to reach a firm conclusion.

If the total circuit heat conversion level and therefore energy input for both setups work out similar, an alternative explanation for the lower lamp brightness in the pulsed setup could then be sought.

Hoppy

[gotoluc]

Hi everyone,

a testing base line needs to be established to better study this circuit effect. That is why I first needed to confirm with .99 what I understood of using a fine filament bulb in series at the input as visual indicator of energy entering the circuit.

I have found that using meters no mater how expensive they are have been giving me false results. Once you makes a change to the circuit, like frequency and or voltage you want to re-tune the duty cycle to send back exactly the same amount of energy to compare the previous test. I know many will say your eye cannot be that accurate. That is right! ... if the intensity of the bulb is high... but if you keep the bulb intensity to the point where it just starts glowing and not go above that you will see that it has an amazing accuracy to show any change in the circuit. Just stay with this technique I just explained and it should work well enough. Also, know that you are not measuring anything with the bulb, it is just a visual indicator of change or a way to re-tune duty cycle after you make a change in order to send back exactly the same amount of energy in the circuit to be able to observe if the change you made is giving you more or less work for the same amount of energy. That is all you want to do at this time. Forget Over Unity proof.

You will understand more after seeing the video's below how I have been using this technique.

Link to test 5: YouTube - Effect of Recirculating BEMF to Coil test 5

Link to test 6: YouTube - Effect of Recirculating BEMF to Coil test 6

Thanks

Luc