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Author Topic: Tesla's "COIL FOR ELECTRO-MAGNETS".  (Read 505776 times)

conradelektro

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Re: Tesla's "COIL FOR ELECTRO-MAGNETS".
« Reply #735 on: January 20, 2014, 04:37:03 PM »
The magnet spinner is finished and the coil is mounted. It does easily 150 Hz, also 200 Hz, but at 200 Hz and above the noise is not good. It did 230 Hz, but one wants to run away because of the vibrations.

On the photo with everything (power supply and scope) the spinner does 150 Hz and the coil produces 5.6 Volt over a 100 Ohm shunt. Coil has 97 Ohm DC resistance. Coil specs see

http://www.overunity.com/13460/teslas-coil-for-electro-magnets/msg383774/#msg383774
http://www.overunity.com/13460/teslas-coil-for-electro-magnets/msg383363/#msg383363

Tomorrow I will start the " resonance and speed up under load tests". Have to go now.

possible tests (10 μF in LC circuit):

70 Hz --- bifilar, steel bolt core (4200 rpm)
120 Hz --- bifilar, air core (7200 rpm)
138 Hz -- monofilar (half coil), steel bolt core (8280 rpm)

248 Hz -- monofilar (half coil), air core not possible (14.880 rpm)
140 Hz -- monofilar (half coil) air core with 30 μF cap in LC circuit (8400)

Greetings, Conrad

tim123

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Re: Tesla's "COIL FOR ELECTRO-MAGNETS".
« Reply #736 on: January 20, 2014, 04:46:44 PM »
Hi Conrad, the build's looking good :)

Just a thought - your bearings & supports are quite far apart - which is probably why you have the vibration problem. If you were to move the bearings closer to the center of the shaft, it might help.

Regards, Tim

synchro1

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Re: Tesla's "COIL FOR ELECTRO-MAGNETS".
« Reply #737 on: January 20, 2014, 06:50:55 PM »
@Conradelektro,


Looks like a ton of bolts! Even if you achieve critical minimum frequency (CMF) for delayed lenz effect (DLE),  with your resonant output coil, your low speed limit won't allow for any meaningful acceleration effect measurement.

gyulasun

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Re: Tesla's "COIL FOR ELECTRO-MAGNETS".
« Reply #738 on: January 20, 2014, 11:12:12 PM »
Hi Conrad,

It is interesting that pancake coils have the magnetic poles in their center area.
Unfortunately I read somewhere the same pole positions like Magluvin described yesterday.
Here is a measurement on the magnetic poles of monofilar and bifilar pancake coils done by a compass
http://www.youtube.com/watch?v=O12UVMFGe2U  It shows the poles also in the center area on the opposite sides of the pancake coil and with his compass he probed the strength of the fields at some distances, both for the mono and bifilar pancake coils but he did not measure difference in field strength between them.

Greetings,  Gyula

MileHigh

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Re: Tesla's "COIL FOR ELECTRO-MAGNETS".
« Reply #739 on: January 21, 2014, 02:48:29 AM »
Gyula:

That was a nice little clip.  Everything measured fine and the edges of the coil looked fine.  There is another fun test as a sideline not related to the investigations.  It's to measure the sizes of the magnetic bubbles in the two main orientations and for say two current levels.

Conrad:

Looking forward to your tests.  Note you are not likely to see any speed-up under load or a speed up at resonance.  It's because you are not using a mosquito-pee pulse motor anymore.  Chances are that the motor will not speed up if you add a load to the pick-up coil.  Just keep in mind that a "classic" "delayed Lenz effect" test is a relatively light load after an FWBR with a mosquito-pee pulse motor.  If you use a matched load resistor and a powerful DC motor the setup has changed.

However, there is a great work-around for that and you will get better data.  The data you get could one day be crunched down to torque and mechanical power by testing with a prony brake, but that's not really necessary.  If you do a basic test where you measure the current consumption of your motor when you add some friction you will probably observe an increase in current consumption but only very small change in the RPM.

Okay, assuming that's true, then do you have a digital multimeter with three digits of precision after the decimal point?  (Gotoluc has a mind-blowing multimeter with five or six digits after the decimal point.)   Assuming that you can measure three digits after the decimal point, then just monitor the current consumption of the motor to observe the "delayed Lenz effect."

Note you have some good data points:  The motor voltage and initial current consumption and delta current consumption between "no delayed Lenz" and "delayed Lenz."  You also have the two RPMs.  You can also assume that the specified efficiency for the motor is correct within +/-10%  (A guess).

So that means you can measure change in average electrical power consumption for the two cases.  So factor in the motor efficiency and that gives you the change in mechanical power.  Then since you know the RPM you can calculate the change in torque when you go from "no delayed Lenz" to "delayed Lenz."

Perhaps the most interesting measurement and follow-up number crunching is the change in average torque and the related change in mechanical power between "no delayed Lenz" and "delayed Lenz."  And of course you can compare that to the change in electrical input power and also measure how much power is going into the pick-up coil load.

Sorry I forgot about making measurements on the output load resistor but I will leave that to others.  You see people sometimes give me a hard time about not experimenting, and at the same time I can easily come up with great experiments.  I threw out all of my 74XXXYY chips, my 4000 series CMOS chips, and my PALs and GALs years ago.  But like the proverbial fish I still know how to swim.

MileHigh

Farmhand

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Re: Tesla's "COIL FOR ELECTRO-MAGNETS".
« Reply #740 on: January 21, 2014, 04:51:36 AM »
I think I remember reading something about the poles of a spiral coil being described by Tesla in a patent or somewhere but I can't recall where. I'll try to find it. I think the gist of it is that it can be modeled as a single turn "height" solenoid but with multiple layers to that one turn height, just my take on it. Another advantage of spiral coil in general is that it negates turn direction in that any spiral coil when turned up side down it appears to be opposite wound, but with a solenoid the same does not apply.

TIM. we don't want a strong magnet spinning too close to those aluminium brackets.

Conrad, might I suggest wooden or plastic blocks drilled and screwed to the base so the uprights can screw to it, maybe with brass or copper screws. The blocks could be mounted outside of the uprights rather than inside. Or as I did a single block could be mounted so that the two uprights screw to the outsides of it.

Cheers

Farmhand

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Re: Tesla's "COIL FOR ELECTRO-MAGNETS".
« Reply #741 on: January 21, 2014, 05:04:46 AM »
MileHigh, I don't agree with your comments above quoted below.

Quote
Note you are not likely to see any speed-up under load or a speed up at resonance.  It's because you are not using a mosquito-pee pulse motor anymore.  Chances are that the motor will not speed up if you add a load to the pick-up coil.  Just keep in mind that a "classic" "delayed Lenz effect" test is a relatively light load after an FWBR with a mosquito-pee pulse motor.  If you use a matched load resistor and a powerful DC motor the setup has changed.

Have a look in this video clip http://www.youtube.com/watch?v=iFWin-crxQY and tell me if you see any mosquito pea motors being used in it. The prime mover is a universal motor powered by about 2 amps from the 12 volt battery so 25 Watts input there, the motor is used under the rated voltage but the torque is not too bad for the input. In the longer (2nd Part of the full) clip you can hear the acceleration of the rotor that happens when I increase the input with the boost converter. It accelerates the rotor with a fair bit of parasitic drag quite easily with the motors torque  ;D Shorting the drag/load coils only speeds it up slowly. hehehehe

The scope shows I used a lower harmonic on the Drag/load coils I believe.

Watch just the beginning of this clip from about 0:38 to 0:53, also at 5:45 to 5:57, I had to be careful to stay under 5 or 6 amps to save my boost converter diodes.  ;)  http://www.youtube.com/watch?v=TV_dm8COKBY to see the current from the battery and the increase in rotor speed by me applying more power, while the parasitic drag is present and in effect trying to slow the rotor.

Also Gesalt's video I think he uses an induction motor for the prime mover. He also got speed up under load.

I can do it with almost any prime mover, it's about creating enough parasitic drag to slow that prime mover, whatever it takes, then removing some of that drag. With a flea-pea pulse motor it takes little with a stronger prime mover it takes more.

The applied load reduces the overall load on the prime mover and a speed up occurs, it's not rocket surgery.

Cheers 

MileHigh

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Re: Tesla's "COIL FOR ELECTRO-MAGNETS".
« Reply #742 on: January 21, 2014, 05:19:49 AM »
Farmhand:

I agree that I am generalizing.  The idea is that with a weak motor when you go from light mechanical load on the rotor to a very light mechanical load on the rotor the weak motor will speed up.  Or to put it another way the weak motor slows down under a light mechanical load.  If, under the same conditions, you replace the weak motor with a strong motor, you won't see the speed change because the strong motor will not have slowed down in the first place.

But it remains to be seen what Conrad does.  My real point being that if his setup looks like the "strong motor" setup as described above, you can measure the motor average current consumption and RPM and do some number crunching and generate some pretty good data:  Measure the change in the output torque of the motor between "no delayed Lenz" and "delayed Lenz."

MileHigh

Farmhand

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Re: Tesla's "COIL FOR ELECTRO-MAGNETS".
« Reply #743 on: January 21, 2014, 05:23:18 AM »
Oh yes you are right, if the motor can draw more current to compensate it may not slow down.

I didn't take into consideration that my boost converter and the circuit resistance in the motor was restricting the input current for me. I should have made that more clear in the video's too I suppose.

You do make a very good point. Point taken.  :)

Cheers

P.S. If you watch right at the end of the clip when I turn off the power to the drive motor how quickly it stops. So the amount of drag I had artificially induced on it was significant.  ;)

Oh and if I had used Bifilar coils maybe that drag might have been less, as I may have needed less external capacitance, but I think it would still have been there just relative to the "tank current". hehe  And also to the "tank energy lost I guess", something like that.

..

Magluvin

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Re: Tesla's "COIL FOR ELECTRO-MAGNETS".
« Reply #744 on: January 21, 2014, 06:17:43 AM »
The coils capacitance is 6.7nf with one meter and 7nf with another. Not sure why.

Im going to wind another tomorrow to see if there is a variance. The wire is so small, as it was winding, the wires could have tracked away from the other. Looked pretty good as it went.  Just doesnt make much sense. I ve wound larger and smaller coils and capacitance grew accordingly. Here it should have been up, but it is down compared to coils with much less turns.  Im beat.  maybe Ill see that I wired it wrong tomorrow.

With calculating L n C it should have rung at near 7.5khz but rings at around 13khz.

Maybe Im just tired and not doing something right.

Mags

Farmhand

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Re: Tesla's "COIL FOR ELECTRO-MAGNETS".
« Reply #745 on: January 21, 2014, 07:53:21 AM »
Mags did you do a test for a short using the continuity function ? Distractions and fatigue can get the better of anyone, temporarily. If something doesn't seem right it probably isn't.

Cheers

gyulasun

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Re: Tesla's "COIL FOR ELECTRO-MAGNETS".
« Reply #746 on: January 21, 2014, 03:13:07 PM »

The coils capacitance is 6.7nf with one meter and 7nf with another. Not sure why.
...

Hi Mags,

You may wish to check the two C meters with a 5.6 nF (or 10 nF) normal capacitor and compare the two values, of course you may have done so?
Also, if you check the measuring frequencies of the C meters with a scope when you measure say an 5.6 nF capacitor with them: perhaps the differing measuring frequencies could also explain the difference.

Gyula

conradelektro

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Re: Tesla's "COIL FOR ELECTRO-MAGNETS".
« Reply #747 on: January 21, 2014, 04:48:27 PM »
I managed to do the first "speed up under load" test, please see the video at

http://www.youtube.com/watch?v=vAXQBpuLu68&feature=youtu.be
(Please read the video info.)

The more the rotor speed goes away from the resonance frequency of about 52 Hz (lower or higher) the more the "speed up under load" diminishes.

25 Hz , no load, motor consumption 2.0 V and 0.82 A
            load, motor consumption 2.0 V and 0.91 A, speed drops to 23 Hz

52 Hz, no load, motor consumption 4.4 V and 1.7 A
           load, motor consumption 4.4. V and 1.09 A, speed rises to 68 Hz
(the magic happens)

110 Hz, no load, motor consumption 6.4 V and 1.06 A
             load, motor consumption 6.4 V and 1.06 A, speed stays at 110 Hz

Please comment and make suggestion for further tests and scope shots. (I will test air core and monofilar, but would like some discussion before I go on, I might do something wrong.)

@MileHigh: thank you again for the help, finally I managed an interesting test. The 12 V DC motor was a great idea. The motor made it simple to build a versatile and stable magnet spinner. I have nor problem with posters who do not do experiments as long as the posts are helpful and state important principles and facts. Posters with relevant knowledge are very rare.

Greetings, Conrad


gyulasun

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Re: Tesla's "COIL FOR ELECTRO-MAGNETS".
« Reply #748 on: January 21, 2014, 06:37:13 PM »
Hi Conrad,

Thanks for your efforts and kind words, very good work! 

As I mentioned in the first few lines of my earlier post ( http://www.overunity.com/13460/teslas-coil-for-electro-magnets/msg383401/#msg383401 ) I suspect the bolt as a core may "trick" the LC circuit by changing its magnetic properties as the AC current inside the tank changes: first when the magnet gets near to the bolt and then starts spinning and second when the 100 Ohm load is attached.  (Perhaps it would be good to check the coil inductance when the magnet is stationary in front of the bolt and the 10 uF cap is disconnected, with both magnet polarity.)

This is why a normal ferrite core would be ALSO good to use, and when you have such (I gave a link to obtain it in my earlier post), then you would  insert it into the coil to have the same resonance what the bolt gave in the unloaded case.
I mention this because the bolt core may "trick the circuit because when you attached the 100 Ohm load, the phase relationship between the current and the voltage in the tank changed from the nearly 90° to almost  180° out of phase.  I suspect this phase shift happens due to the permeability change in the bolt due to the much less current amplitude in the tank: in the unloaded case the tank current is 108 mA and in the loaded case it is 56 mA.

I believe the effect of this change in the excitation current would not influence a ferrite core's permeability as much. I mainly consider here the eddy current losses in the bolt: it increases when excitation is increased and vice versa.

You may have noticed that the voltage amplitude across the tank decreased to a too low value (from 31.2 V rms to 4.8 V rms) when you attached the 100 Ohm load: if the load is matched to the generator, then the loaded output voltage may have half the value of the unloaded output, in this case it should be around 15.5 V instead of the measured 4.8 V. This may indicate that the inductive reactance of the coil changes as per the excitation i.e. by the AC current magnitude in the tank, hence influencing the Quality factor of the coil, hence influencing the generator output impedance. 

Perhaps you happen to have a 470 or 1000 or even a 2200 Ohm variable resistor, either a trimmer or a normal potmeter and you may wish to use it instead of the fix 100 Ohm to adjust the 15.5 V AC rms across the tank and also slightly adjust the motor speed to reastablish the best resonance (because the changing load affects the core magnetic properties).

So it is very good you show the tests with the bolt core. 

Greetings,  Gyula

conradelektro

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Re: Tesla's "COIL FOR ELECTRO-MAGNETS".
« Reply #749 on: January 21, 2014, 06:52:15 PM »
I did some more tests with one wire only (still the steel bolt as core).

wires in parallel, mild steel core  (DC resistance 20 Ohm)

110 Hz, no load, motor consumption 7.3 V and 1.79 A
              load, motor consumption 7.3 V and 1.06 A, speed rises to 130 Hz
 

only thicker wire, mild steel core (other wire open, DC resistance 27 Ohm)

110 Hz, no load, motor consumption 7.1 V and 1.64 A
              load, motor consumption 7.1 V and 1.01 A, speed rises to 126 Hz
 

only thinner wire, mild steel core
(other wire open, DC resistance 70 Ohm)

100 Hz, no load, motor consumption 6.5 V and 1.44 A
              load, motor consumption 6.5 V and 1.1 A, speed rises to 113 Hz


It look s like the DC resistance of the wire has an influence?

I will proceed to tests with air core. I have a Ferrite rod which just does not fit into the hole of the coil. I will try to widen the hole a little bit. But I do not want to do that till I have enough measurements with air core and steel bolt core (the coil might be damaged when manhandling it).

 Greetings, Conrad