Tesla's "COIL FOR ELECTRO-MAGNETS".

[gyulasun]

....

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

Hi Conrad,

Okay, just do your schedule as you wish I have no intention to "divert" anything.

In your above tests,  you used the same 10 uF tuning capacitor?

The DC resistance establishes a basic coil loss resistance and this latter establishes mainly the current via the coil: hence this influences the core's excitation I believe.

Gyula

[conradelektro]

Hi Conrad,

Okay, just do your schedule as you wish I have no intention to "divert" anything.

In your above tests,  you used the same 10 uF tuning capacitor?

The DC resistance establishes a basic coil loss resistance and this latter establishes mainly the current via the coil: hence this influences the core's excitation I believe.

Gyula

@Gyula: I always used the same 10 µF capacitor (yellow thing, I only have three, and two are in a box). No problem with suggestions, you are not diverting, you are teaching.


New test with air core (all the same, only the steel bolt was removed and coil is a bit closer to spinning magnet, 3 mm gap):

wires in series, air core (DC resistance 97 Ohm)

125 Hz, no load, motor consumption 7.3 V and 1.18 A
             load, motor consumption 7.3 V and 0.94 A, speed rises to 133 Hz


For comparison:

wires in series, mild steel core (DC resistance 97 Ohm)

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


For test with only one wire (mild steel core) see: http://www.overunity.com/13460/teslas-coil-for-electro-magnets/msg384176/#msg384176

Greetings, Conrad

[conradelektro]

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.

@tim123: yes, of course, but I wanted some space left and right of the spinning magnet for bigger pan cake coils. Thank you, every observation helps and brings me forward.

The biggest unbalance is the magnet, one even sees how one halve is slightly bigger than the other. I might try some counterweight on the axis.

Greetings, Conrad

[Farmhand]

The thing I looked at with the speed up under load effect is the dismal output as compared to the input, overall a faster rotor is not output, the power dissipated by the load resistor is the output, and the input compared to that.

Conrad try this if you don't mind, set the arrangement to the resonance point you get at 52 Hz or whatever it is how you have it, then after connecting the load adjust the drive motor to try to increase the voltage across the generator coil. Re tune the setup in other words, What I expect will happen is the output power dissipated by the resistor will increase and possibly change the efficiency somehow. It looks like you could tune it easily while loaded.

What I looked at was the efficiency of input to output. And a more lower input and faster rotor were a novelty compared to the tragic efficiency. Both loaded and unloaded as compared to a well designed and efficient "meets the load generator".

If you got 5.6 volts across the load resistor of 97 Ohms that works out to less than 0.4 of a watt. And if the input is some 3 or 4 volts at one amp when loaded then that is 3 or 4 Watts. Something to consider.

Cheers

[conradelektro]

The thing I looked at with the speed up under load effect is the dismal output as compared to the input, overall a faster rotor is not output, the power dissipated by the load resistor is the output, and the input compared to that.

Conrad try this if you don't mind, set the arrangement to the resonance point you get at 52 Hz or whatever it is how you have it, then after connecting the load adjust the drive motor to try to increase the voltage across the generator coil. Re tune the setup in other words, What I expect will happen is the output power dissipated by the resistor will increase and possibly change the efficiency somehow. It looks like you could tune it easily while loaded.

What I looked at was the efficiency of input to output. And a more lower input and faster rotor were a novelty compared to the tragic efficiency. Both loaded and unloaded as compared to a well designed and efficient "meets the load generator".

If you got 5.6 volts across the load resistor of 97 Ohms that works out to less than 0.4 of a watt. And if the input is some 3 or 4 volts at one amp when loaded then that is 3 or 4 Watts. Something to consider.

Cheers

Attached are the scope shots for the air core test (the phase shift of the current is still similar to the mild steel core test).

Scope shot of "mild steel core test" see here http://www.overunity.com/13460/teslas-coil-for-electro-magnets/msg384149/#msg384149


@Farmhand: The coil with air core seems to have a maximum output over the 100 Ohm resistor at about 200 Hz, at 240 HZ it definitely puts out less, also below 200 Hz.

The output is very low compared to the demands of the DC motor ( ~0.3 Watt versus ~4 Watt). It is a very bad generator, but it is intended to measure the "speed up under load" and not "generator design". You are right, there are many things to consider if maximum output is the goal.


@all: General observation

My feeling is that the "speed up under load" or the "delayed Lenz effect" has something to do with "resonance of the coil with its self capacitance", which can be shown at lower frequencies with an "external parallel LC circuit capacitor of high capacitance" (such simulating the resonance condition at an artificially lowered frequency).

To spin this haphazard theory a bit further: if the generator coil is in this "resonance condition" it introduces heavy losses and the losses are reduce if a load pulls the generator coil out of the resonance condition. Therefore the "speed up under load" and the "reduced power consumption of the drive motor under load".

May be I am wrong, but my tests point in this direction.

Greetings, Conrad